Scanning Electron Microscopy in Archaeology 9780860545798, 9781407347370

Citation preview

Scanning Electron Microscopy in Archaeology

edited by

Sandra L. Olsen

BAR International Series 452

1988

B.A.R. 5, Centremead, Osney Mead, Oxford OX2 ODQ, England.

GENERAL EDITORS A.R. Hands, B.Sc., M.A., D.Phil. D.R. Walker, M.A.

BAR -S452, 1988: 'Scanning Electron Microscopy in Archaeology' © The Individual Authors, 1988

The authors’ moral rights under the 1988 UK Copyright, Designs and Patents Act are hereby expressly asserted. All rights reserved. No part of this work may be copied, reproduced, stored, sold, distributed, scanned, saved in any form of digital format or transmitted in any form digitally, without the written permission of the Publisher. ISBN 9780860545798 paperback ISBN 9781407347370 e-book DOI https://doi.org/10.30861/9780860545798 A catalogue record for this book is available from the British Library This book is available at www.barpublishing.com

D edicated t o D on B rothwell, w ho f oresaw t wenty y ears a go t he g reat c ontributions s canning e lectron m icroscopy h as t o o ffer a rchaeology.

CONTENTS Part I:

Methods and Techniques

SANDRA L. OLSEN: Introduction: Applications Electron Microscopy to Archaeology. DONALD CLAUGHER: Viewing Uncoated MEEKS: NIGEL Archaeological

Preparative Materials.

Methods,

Scanning

Replicating, and Imaging

Electron

Backscattered Materials.

of

of

9

23

Archaeometallurgy

Part II:

A. DAVID Complementary

SCOTT: Methods

SEM of

Analysis:

Microprobe and Investigation.

DANA E. GOODBURN-BROWN: Metalworking Tools and Practices: Interpretation of Worked Metal Rubber Moulds. Silicone via

Part III:

Workshop Surfaces Material

of Organic Products.

WATSON: Identification JACQUI Metal Corrosion Preserved by

47

55 65

Pottery

DONALD J. BLAKESLEE and RICHARD K. DUNN: Subsoil Inclusions in Pomona Ceramics. Part IV:

Stone

Artifacts

and

Identification

of

Grains Studies: Archaeologists by

Chemical Etching KJEL KNUTSSON: Experimental Quartz Tools.

Wear

FRANCESCO Study of

d'ERRICO: The Use Lithic Use-Wear.

of

Features

of

Resin

Replicas

FRANCESCO d'ERRICO: A Study of Epipaleolithic Engraved Pebbles.

Upper

Paleolithic

Plant

79

Mineralogy

P. A. BULL and A. W. MAGEE: Quartz for Reconstruction Environmental Scanning Electron Microscopy.

Part V:

3

for

on the and

103 117 155 169

Materials

JULIET PRIOR: Methods Used in Charcoal the Relationship between Woods Used in Times and the Present Fuelwood Crisis.

iii

and Analysis Archaeological

187

BRUCE

D .

SMITH:

Morphological

S EM

and

t he

I ndicators

of

I dentification

Domestication

of

i n

M icro-

S eed

P lants. E .

2 03

ANN

BUTLER:

Particular SUSAN

M .

The

S EM

Reference COLLEDGE:

Animal

T IM YATES: Marine

I dentification,

w ith 2 15

Some

Wild

Wheats

a nd

Ryes. 2 25

Materials

T he Detection of Diagenetic C hanges i n Non-

S IMON

H ILLSON: of

PAT

S eed

V icieae.

S hells.

S tudy

a nd

the

S EM S tudies o f t he C ell P atterns o f t he

Pericarp Layers o f Methods and P roblems. Part V I:

a nd

t o

2 39 The

Ancient

S HIPMAN: Hominid

FRIEDEMANN

S canning

Electron

Microscope and

t he

Teeth.

2 49

Actualistic

S tudies

o f

Animal

Resources

Activities. SCHRENK:

Makapansgat

2 61

Actualistic

Limeworks

Bone

PAT S HIPMAN and JENNIE ROSE:

SEM

S tudies

on

t he

Breccia. Bone

2 87

Tools:

An

Experimental

Approach. SANDRA Tool

3 03

L .

Part V II: P .

OLSEN:

Marks

F .

on

The I dentification

Bone

Hominid

P UECH,

Fluoride

F .

o f

S tone

and

Metal 3 37

Artifacts.

Remains C IANFARANI,

Content

and

A .

MARKITZIU,

Microwear

of

and I .

Teeth

i n

GEDALIA:

the P eninj 3 64

Australopithecus. KEITH

DOBNEY

Microscope YOLANDA Buccal

DON of

BROTHWELL: Archaeological

FERNANDEZ-JALVO and S triations

Atapuerca CATRYN

and

S tudy

on

t he

A

S canning

Dental

Electron 3 72

C alculus.

JOSE MARfA BERMÜDEZ d e CASTRO: Hominid

Anterior

T eeth

f rom 3 86

( Spain).

POWER

I nterproximal

a nd V .

R .

Abrasion

O 'SULLIVAN: Grooves

i n

i v

The

O ccurrence

o f

Some I rish P opulations.

4 02

L IST O F C ONTRIBUTORS J ose M aria B ermüdez d e C astro M useo Nacional d e C iencias N aturales J ose G utierrez Abascal,

2

2 8006 Madrid S pain D onald J .

B lakeslee

D epartment o f Anthropology T he W ichita S tate U niversity Wichita,

Kansas 6 7208

U .S.A . D on B rothwell D epartment o f Human E nvironment I nstitute o f Archaeology U niversity C ollege U niversity o f L ondon 3 1-34 Gordon S quare L ondon,

E ngland WC1H OPY

P eter A .

B ull

S chool o f G eography U niversity o f O xford O xford, E .

England OX1 3 TB

Ann Butler

D epartment o f Human E nvironment I nstitute o f A rchaeology U niversity C ollege U niversity o f L ondon 3 1-34 Gordon S quare L ondon,

E ngland WC1H OPY

Frangois C ianfarani D epartment o f F orensic M edicine Faculte d e M edecine L a T imone 2 7 B d J ean M oulin Marseille C edex 5 F rance 1 3

3 85

D onald C laugher E lectron Microscope U nit B ritish Museum ( Natural H istory) C romwell Road, London,

England S W7 5 BD

S usan C olledge D epartment o f Human E nvironment I nstitute o f Archaeology U niversity C ollege U niversity o f L ondon 3 1-34 G ordon S quare L ondon,

E ngland W C1H O PY

K eith D obney D epartment o f A rchaeology B radford U niversity B radford,

E ngland

R ichard K . D unn D epartment o f G eology T he W ichita S tate U niversity W ichita,

K ansas 6 7208

U .S.A . F rancesco d 'Errico Laboratoire d e P rehistoire, C .N.R.S.

U .A .

1 84

I nstitut d e P aleontologie Humaine

1 R ue R ene P anhard 7 5013 P aris F rance a nd Human P aleontology L aboratory D epartement o f Human P aleontology a nd P hysiology U niversity o f T urin C orso M . 1 0126,

D ' Azeglio 5 2

I taly

Y olanda F ernAndez-Jalvo M useo N acional d e C iencias Naturales J ose G utierrez Abascal, 2 8006 M adrid,

2

S pain

I tzhak G edalia D ental R esearch H ebrew U niversity Hadas s ah S chool o f D ental M edicine J erusalem, D ana E .

I srael 9 1

1 20

G oodburn-Brown

M useum o f L ondon L ondon,

E ngland

v i

S imon H illson D epartment o f Human E nvironment I nstitute o f A rchaeology U niversity C ollege U niversity o f L ondon 3 1-34 Gordon S quare L ondon,

E ngland WC1H O PY

K jel K nutsson D epartment o f A rchaeology U ppsala U niversity U ppsala,

S weden S -75220

A lfred W .

Magee

S chool o f G eography U niversity o f O xford O xford,

E ngland OX1 3 TB

J udy M .

M aguire

B ernard P rice I nstitute f or P alaeontological R esearch U niversity o f t he Witwatersrand J ohannesburg 2 001,

S outh A frica

A lice Markitziu O ral D iagnosis H ebrew U niversity Hadassah S chool o f D ental Medicine J erusalem, N igel D .

I srael 9 1120

Meeks

T he B ritish Museum R esearch Laboratory G reat R ussell S treet L ondon,

E ngland WC1B 3 DG

S andra L .

O lsen

D epartment o f C ell B iology a nd Anatomy T he J ohns Hopkins U niversity S chool o f M edicine 7 25 N orth Wolfe S treet B altimore,

Maryland 2 1205

U .S.A . V .R.

O 'Sullivan

D epartment o f Anatomy U niversity C ollege C ork C ork, C .

I reland

P ower

D epartment o f Archaeology U niversity C ollege C ork C ork,

I reland

v ii

J uliet P rior D epartment o f P ure a nd Applied B iology I mperial C ollege o f S cience a nd T echnology P rince C onsort Road L ondon,

E ngland S W7 2 BB

P ierre-Fran cois P uech D epartment o f P rehistory M us e d e l 'Homme d e P aris B .P.

1 91,

2 r ue S aint-Antoine

Nimes C edex,

F rance 3 0 0 08

J ennie Rose D epartment o f C ell B iology a nd Anatomy T he J ohns H opkins U niversity S chool o f M edicine 7 25 N orth Wolfe S treet Baltimore,

Maryland 2 1205

U .S.A . Friedemann S chrenk H essisches Landesmuseum Friedensplatz 1 6 100 D armstadt West G ermany David S cott T he G etty C onservation I nstitute 4 503B G lencoe Avenue Marina d el R ey,

California 9 0292-6537

P at S hipman D epartment o f C ell B iology a nd Anatomy T he J ohns Hopkins U niversity S chool o f Medicine 7 25 N orth Wolfe S treet Baltimore, Maryland 2 1205 U .S.A . B ruce D .

S mith

D epartment o f Anthropology N ational Museum o f N atural H istory/National Museum o f Man S mithsonian I nstitution Washington,

D .C.

2 0560

U .S.A . J acqui Watson Ancient Monuments Laboratory H istoric B uildings a nd Monuments C ommission f or E ngland Fortress H ouse 2 3 S avile R ow L ondon,

E ngland W 1X 2 HE

v iii

T im Yates D epartment o f Geography U niversity College U niversity o f London G ower S treet L ondon,

England WC1H OAP

i x

P ART I :

METHODS AND T ECHN IQUES

INTRODUCTION: ARCHAEOLOGY

APPLICATIONS

O F

S CANNING

ELECTRON

M ICROSCOPY

T O

S andra L . O lsen

T his

v olume

i s

E lectron M icroscopy

t he

p roduct

o f

i n A rchaeology,

a c onference

h eld

i n

1 986,

a t

e ntitled t he

S canning

I nstitute o f

A rchaeology, t he U niversity o f L ondon. A g athering o f o ver 6 0 s cientists f rom 1 0 n ations s pent t wo d ays p resenting t heir r esearch a nd o penly d iscussing t heir m ethods. I t w as a r are o pportunity f or a rchaeologists, c onservators, a nd s pecialists f rom a n umber o f o ther f ields t o s hare t heir v iews a nd e xchange i deas a bout t he p otential u ses o f s canning e lectron m icroscopy ( SEM) t o a m yriad o f s cientific p roblems. T he r esults w ere r ewarding: r esearchers w ho w ork o n v ery d ifferent m aterials f ound t hat m any o f t he d ifficulties t hey h ad e ncountered w ere s hared b y o thers a nd t hat, b y i nteracting w ith e ach o ther, t hey c ould d iscover s olutions t o t hese p roblems. A s a r esult o f t his m eeting, t hose w ho p resented p apers, a nd o thers w ho s ubsequently c ame f orward, h ave c ontributed t o t his v olume t o f urther d isseminate i nformation

o n

m ethods

o f p reparation o f

a rchaeological

s pecimens

a nd

a pplications o f S EM t o t he a nalysis o f a rchaeological d ata. B rothwell

( 1969)

w as

o ne o f

t he

f irst

t o a dvocate

t he u se o f S EM

i n t he a nalysis o f a rchaeological s amples. H e p ointed o ut t he a dvantages o f S EM o ver o ptical m icroscopy, d emonstrating h ow i t c ould b e u sed t o s tudy a ncient b one, d entition, t extile f ibers, h air, p lant r emains, a nd s tone t ools ( Brothwell 1 969: 5 64-566). I t i s c lear, b y t he d iversity o f s ubjects c overed i n t his v olume a nd t he i ncreasing r eference t o s canning e lectron m icroscopy i n r ecent p ublications, t hat SEM has become an important t ool i n t he i nterpretation o f a rchaeological d ata. T he S EM h as b een s hown t o h ave n umerous s pecific a pplications o n a wide v ariety o f m aterials, b ut b ecause o f t ime, e xpense, a nd d ifficulties i nvolved w ith s pecimen p reparation, i t i s r arely u sed i n e xclusion o f o ther a nalytical i nstruments. I n f act, o ne o f t he g reat s trengths o f S EM i s i ts c omplementarity w ith o ptical m icroscopes. W hereas t he o ptical m icroscope p rovides a s imple a nd i nexpensive m eans o f a nalyzing b ulk s amples, t he S EM a chieves a h igher s tandard o f a nalysis o n a g reatly r educed p opulation o f o bjects. T he w ell-known a dvantages

o f

t he

s econdary e lectron e mission m ode

o ver o ptical m icroscopy a pply t o t he s tudy o f a rchaeological m aterials a s w ell a s o ther o bjects. T hese i nclude: t he v ast, c ontinuous r ange o f m agnifications g reatly e xceeding t he o ptical l imit o f a round 1 000 t imes, t he i ncreased d epth o f f ield ( which i s a bout 3 00 t imes g reater t han f or a n o ptical m icroscope), a nd t he h igh r esolution ( practically s peaking a round 2 00 9 i i n t he S EM).

A ll o f t hese f eatures a re i mportant

r easons f or c hoosing S EM f or a rchaeological a nalysis o f m icroscopic s urfaces. E ven a t l ow m agnifications t he h igh q uality o f s canning e lectron m icrographs a nd s tereo-pairs e nables t he r esearcher d emonstrate h is o r h er f indings c learly i n p ublished f orm . M ost p rimarily

a rchaeological s tudies w ith t he o bservation o f

t o

w hich e mploy S EM a re c oncerned s urface t opography a nd, t herefore,

3

r ely m ainly o n t he s econdary e lectron i mage ( SEI). M uch o f t he w ork i nvolves l ow m agnifications b etween 1 0 a nd 1 ,000 t imes, a lthough s pecific p roblems m ay o ccasionally r equire h igher m agnifications. A w ide r ange o f a rchaeological m aterials i ncluding m etals, g lass, f aience, p ottery, s tone, s oil p articles, p igments, b one, t eeth, f ingernails, s kin, h air, e ggshell, m ollusks, i nsects a nd p arasites, p lant r emains, w ood, p ollen, s econdary e lectron i maging.

f ibers,

a nd s o o n h ave b een e xamined w ith

T he s econd m ost c ommon u se o f t he S EM i s f or d etermining c omposition, g enerally u sing e nergy d ispersive x -ray a nalysis ( EDAX). T he a dvantages o f u sing x -ray m icroanalysis w ith a S EM a re n umerous. I t p rovides a r elatively q uick a nd n ondestructive m eans o f o btaining q ualitative i nformation o n t he c onstituents o f am aterial w ithout m uch s pecimen p reparation. A t t his l evel t he s ample m ay o nly n eed t o b e c oated w ith c arbon, u nless i t i s s ufficiently c onductive w ithout c oating. F or m ore q uantitative s tudies t he s ample m ay n eed t o b e s ectioned a nd p olished, b ut t his s till a llows t he s pecimen t o b e u sed f or o ther f orms o f a nalysis. A n x -ray m icroprobe i s s ometimes p referred b ecause o f i ts s uperior q uantitative r esults, b ut s ince t hese i nstruments a re g enerally m ore e xpensive a nd l ess c ommon, a ccess m ay b e l ess c onvenient t han f or a S EM-EDAX. X -ray m icroanalysis h as b een u sed b y r esearchers o n m etals, c eramics, g lass, f aience, b one, a nd o ther a rchaeological materials. E lemental m apping h as b een e xtremely e nlightening i n t he s tudy o f m etal a lloys a nd f or i dentifying i nclusions i n p ottery. B ackscattered e lectron i maging ( BEI) h as s een m ore l imited a pplication, b ut h as t he a dvantage o f s upplying b oth t opographic a nd c ompositional i nformation s imultaneously. I t a lso e liminates t he p roblem o f t he e dge b right-up e ffect d ue t o c harging, a c ommon p roblem w ith a rchaeological s pecimens t hat a re p oorly c onductive. T his i s e specially i mportant i f t he e dge o f t he o bject i s t he c hief a rea o f s tudy a s i n w ear a nalysis o f s tone, b one, o r m etal t ools ( Meeks, e t a l., 1 982). Cathodoluminescence ( CL) h as r eceived l ittle a ttention b y a rchaeologists, b ut i t h as b een s hown t o h ave v alue i n t he e xamination o f q uartz g rains b y s oil a nalysts ( Krinsley a nd H yde, 1 971) a nd f or d etermining t he l ikely s ources o f t hermoluminescence s ignals i n p rehistoric c eramics ( Singhvi a nd Z immerman, 1 979). A uger e lectron e mission i s o ne o f t he l east c ommonly e mployed S EM m odes i n a rchaeology. T his may b e d ue t o a c ombination o f l imited a ccessibility t o m icroscopes w ith A uger d etectors a nd a l ack o f c ommon k nowledge a mong a rchaeologists a bout t he p rinciples a nd a pplications o f t his m ode. I n o ne c ase, h owever, A uger e lectron s pectroscopy w as u sed t o a nalyze t he c onstituents o f G reek b ronze a rrow t ips ( Polak e t a l., 1 983).

P reparation M ethods f or Archaeological S pecimens W orking samples a re m icroscope.

w ith a rchaeological m aterials m ay p ose p roblems w hen p repared f or e xamination w ith a s canning e lectron S ometimes a rchaeological s pecimens a re r eplaceable o r

4

a vailable i n v ast q uantities, a s w ith s oil s amples, p ollen, a nd c ertain k inds o f s tone, b one, o r p ottery c ollections. I n t hese c ases i t i s e asy e nough t o j ustify t he s ectioning, m etal-coating, o r o ther d estructive a lterations n ecessary f or o ptimal o bservation i n t he S EM. V ery o ften t his i s n ot t he c ase, h owever, a s w hen t he s amples a re u nique o r v ery r are a nd c onservation b ecomes a p rimary c oncern f or t he r esearcher. I n t hese s ituations a lternative m ethods o f s pecimen p reparation m ust b e f ound, s uch a s t he a voidance o f c oatings a nd a dhesives, t he s election o f f ragments o f m aterial s mall e nough t o f it i nto t he c hamber w ithout s ectioning, o r t he u se o f r eplicas. T hought m ust b e g iven t o t he k inds o f a nalysis t o b e p erformed o n t he s ample b efore a ny p reparation i s c arried o ut. F or e xample, i f m icroanalysis i s t o b e c onducted, o bviously t he s pecimen s hould b e c oated w ith c arbon r ather t han a m etal a lloy, s uch a s g old-palladium. I n s ome c ases f urther a nalytical t echniques m ay n eed t o b e p erformed a fter S EM o bservation, r equiring c areful p lanning d uring p reparation. O n r are o ccasions, t he s ample m ay b e l ater r adiocarbon d ated, i n w hich c ase c ontamination b y c oatings a nd a dhesives s hould b e a voided. W henever p ossible t he u se o f c oatings a nd a dhesives s hould b e r estricted t o s amples t hat a re c onsidered e xpendable o r r eplaceable; i f s everal k inds o f a nalysis a re t o b e p erformed o n a g iven s ample, t hen t he m ost d estructive t ests o r p reparation t echniques s hould b e d one l ast. I t i s n ot u nusual f or s pecimens t o b e h oused a nd m useum w hich d oes n ot h ave a l oan p olicy f or i ndividuals o r w ill n ot a llow m odifications t o b e p erformed o n t he t hese s ituations t he r esearcher m ay f ind i t n ecessary t o s pecimen i n o rder t o s tudy i t a t o ther f acilities d estructive t reatment o f t he o riginal.

c urated i n a o r f oreigners o bjects. I n r eplicate t he o r t o a void

I n a ddition t o p roblems p ertaining t o t he c onservation m easures a ssociated w ith t he c are a nd h andling o f r are a rchaeological s amples, m any o f t he d ifficulties e ncountered i n p reparation a re s pecifically related t o t he n ature o f t he m aterial e xamined. T he s ize, c onductivity, p orosity, a nd s tate o f p reservation o f a rchaeological s amples a re t he c hief s ources o f p roblems w ith p reparation. W ith i ncreasingly l arger S EM s pecimen c hambers, a rchaeologists n ow h ave m ore f reedom t o s tudy w hole a rtifacts w ithout t he n eed t o r eplicate o r s ection t hem . T he o ption o f v iewing s mall f ragments r ather t han c omplete o bjects i s v ery o ften f easible, s ince s o many a rchaeological m aterials a re f ragmentary w hen r ecovered. E ven w ith a l arge v acuum c hamber,

s ize l imitations m ay s till b e a

s erious p roblem i f t he m aterial i s v ery p orous. B one a nd a ntler, e xample, a re p roblematical s ince i t m ay b e d ifficult t o e vacuate

f or t he

c hamber i f l arge s amples a re u sed. P lacement o f s pecimens i n a d esiccating c hamber f or t wo t o t hree d ays p rior t o o bservation i n t he S EM c an f acilitate o utgassing. I f a C harge F ree A nticontamination S ystem ( CFAS) i s i ncorporated i n t he S EM, t hen l arge, p orous s pecimens c an b e s tudied. T he C FAS m aintains a s ignificant v acuum d ifferential b etween t he c olumn a nd t he c hamber, s o t hat o bjects c an b e v iewed i n a p oor v acuum . T he r esults

5

a re s ignificant f or a rchaeologists, s ince n ot o nly c an l arge s amples b e s tudied, b ut a lso n onconductive s amples c an b e v iewed w ithout c oating ( Claugher, t his v olume). I f a C FAS i s n ot a vailable, t hen t he c onductivity o f t he a rchaeological m aterial i s i mportant. A s m entioned a bove, m etal c oating a ncient

m ay n ot a lways b e a v iable p rocedure w ith r are o r v aluable o bjects o r t hose t hat w ill b e d isplayed i n m useum e xhibits.

T here a re s everal a lternatives t o m etal c oating, h owever, w hich m inimize t he p roblem o f c harging c onsiderably. M any a rchaeological m aterials

a re

s ufficiently

c onductive

w ithout

c oating

i f

c ertain

p recautions a re o bserved a nd i f o nly l ow m agnifications a re t o b e u sed . T ransparent a nti-static c oatings c an b e a pplied j ust p rior t o v iewing t o r educe c harging w ith n o v isible d eleterious e ffects. S lowing t he s canning s peed, r educing t he a ccelerator v oltage a nd m inimizing t he v iewing t ime p rior t o p hotographing a p articular a rea w ill a ll h elp a void c harging e ffects. W rapping a m etal w ire a round t he o bject a nd t wisting i ts e nds a round t he s pecimen m ount w ill h elp d rain o ff c harging, a s w ell. I t h as b een f ound t hat s tone, b one, s hell, p ottery, a nd m etals c an u sually b e s tudied a t m agnifications u nder 1 000 t imes i f t he a bove r ecommendations a re f ollowed. W henever p ossible, s uch a s w hen s amples a re e xpendable, o r w hen e xperimental i mitations a re t o b e e xamined, i t i s c learly p referable t o c oat t he o bject w ith g old-palladium f or n ormal i maging o r c arbon f or m icroanalysis a nd t o a ttach t he s pecimen f irmly t o a s tub w ith a c onductive a dhesive s uch a s s ilver o r c arbon d ag. I n m any c ases t he b est s olution f or S EM a nalysis o f a rchaeological s amples i s t o r eplicate t he a rea t o b e s tudied . T he m ost c ommon p rocedure i s t o m ake a s ilicone r ubber m ould o f t he s urface o f t he o bject. T he n egative r eplica c an t hen b e c overed w ith a c onductive m etallic c oating a nd v iewed d irectly i n t he S EM, o r i t c an b e u sed t o p roduce a p ositive r esin r eplica f or s tudy. C onsiderable i nformation h as b een p ublished o n r eplicating t echniques w ith u seful c omparisons b etween d ifferent c ommercial p roducts ( Pfefferkorn a nd B oyde, 1 974; P ameijer, 1 979; L arsen, 1 979; d 'Errico e t a l., 1 982/83; R ose, 1 983; B romage,

1 985).

C onclusions A lthough

t his

v olume

d oes

n ot

e xplore

t he

f ull

p otential

o f

s canning e lectron m icroscopy i n a rchaeological a nalysis, i t i s h oped t hat t he r eader w ill b e p rovided w ith a s ample f rom t he r ange o f possible applications. A s l esser-known S EM m odes, s uch a s c athodoluminescence a nd A uger e lectron e mission b ecome m ore c ommon, t heir u se i n a rchaeology w ill u ndoubtedly i ncrease. S canning e lectron m icroscopes a re, t hemselves, b ecoming m ore r eadily a vailable a nd a ffordable, s o t he s ize o f s amples w hich c an b e s tudied w ith S EM i s r apidly e xpanding. T he i mprovements i n i maging t hrough f rame s torage a nd d igitalizing, a s w ell a s o ther c omputerized f eatures, i ncrease t he q uality o f i nformation o btained t hrough S EM . O ne o f t he m ost i mportant p oints w hich c ontributors i n t his v olume h ave a ttempted t o c onvey i s t he c omplementarity o f S EM w ith o ther f orms o f a nalysis. I t i s n ot v iewed a s a s ubstitute o r r eplacement f or o ptical m icroscopy, b ut

6

rather

an

independent

means

o f

c ontributing

i nformation

t o

a rchaeological r esearch.

References B romage,

T .

1 985.

S ystematic

r eplica c ombinations f or S EM. B rothwell,

D .

1 969.

i nquiry

i n

t ests

o f

n egative/positive

J ournal o f M icroscopy 1 37(2):

2 09-216.

T he s tudy o f a rchaeological materials by means o f

t he s canning e lectron m icroscope: a n i mportant n ew f ield. C hapter 4 8 i n D . B rothwell a nd E . H iggs ( eds.), S cience i n A rchaeology, pp. 5 645 66.

T hames a nd H udson,

C laugher, D . 1 987. u ncoated materials. i n A rchaeology. d 'Errico, 1 1:

S econd e dition,

r evised a nd e nlarged.

P reparative methods, r eplicating a nd v iewing o f I n S .L. O lsen ( ed.), S canning E lectron M icroscopy

B AR I nternational S eries,

F .,

r eplicas:

L ondon.

G iacobini,

a n ew method

G .

f or

a nd

London.

P uech,

P .F.

1 982/1983.

Varnish

t he s tudy o f w orked bone s urfaces.

O ssa 9 -

2 9-51.

K rinsley,

D .H.

s ediments. M icroscope

a nd H yde,

P .J.W .

P roceedings

o f

S ymposium P arts

1 971. t he

I a nd

C athodoluminescence s tudies o f

F ourth

I I:

Annual

4 11-413.

S canning

E lectron

I IT R esearch I nstitute,

C hicago. Larsen,

E .B.

1 979.

C onservation, M eeks,

N .D.,

M oulding a nd C asting o f Museum Objects.

d e G .

S ieveking,

G .,

T ite, M .S.

a nd C ook,

J .

a nd u se-wear t races o n f lint s ickles a nd s imilar phenomena. A rchaeological S cience 9 :

G .

G loss

J ournal o f

t echniques w ith n ew d ental d ifferent n egative i mpression

S canning E lectron M icroscopy 1 979/II:

P fefferkorn,

1 982.

3 17-340.

P ameijer, C .H. 1 979. R eplication i mpression materials i n c ombination w ith materials.

S chool o f

C openhagen.

a nd B oyde,

A .

s canning e lectron m icroscopy.

1 974.

5 71-574.

R eview o f r eplica t echniques f or

S canning E lectron M icroscopy 1 974/I:

7 5-

8 2. P olak, M ., a pplied

t o

Baram, t he

2 5(1):

5 9-67.

Rose,

J .J.

J .

1 983.

m icroscopy:

a nd P elleg,

a nalysis

A

a pplications

o f

A .K .

f ine-grain

a nd

s amples

f or

Z immerman, f rom

1 983.

r eplication

P hysical A nthropology 6 2(3): S inghui,

J .

Auger e lectron s pectroscopy

a rchaeological

a rtifacts.

t echnique

f or

a nthropologists.

Archaeometry

s canning

American

e lectron

J ournal

o f

2 55-261. D .W .

1 979.

a rchaeological

7 3-77.1

7

T he

l uminescent m inerals i n

c eramics.

Archaeometry

2 1(1):

P REPARATIVE M ETHODS, R EPLICATING, AND V IEWING OF U NCOATED MATERIALS D .

C laugher

I ntroduction S ince t he a dvent o f t he f irst S EM i n 1 965 d esign h as i mproved a nd m icroscopes h ave b ecome m ore v ersatile. E arly S EMs w ere o nly c apable o f p roducing s econdary e lectron i mages, b ut q uite r apidly i t w as f ound t hat a nalytical f acilities c ould b e i ncorporated t ogether w ith a n umber o f a lternative m ethods o f i maging. I n s hort t he S EM b ecame a u niversal t ool f or s cientists i n a l arge n umber o f d isciplines. D espite

t he

i mprovement

o f

t he

m icroscope,

o ne

t hing

h as

n ot

c hanged, a nd t hat i s i ts i nability t o p roduce a f irst c lass i mage f rom p oorly p repared s pecimens. M any p eople i nvolved i n t he p reparation o f material f or S EM e xamination g ive l ittle t hought t o s pecimen p reparation a nd t his l ack o f t hought, o r p erhaps l ack o f u nderstanding, l eads i nvariably t o d isappointing r esults, f or w hich t he i nstrument o r t he o perator i s b lamed. I n a ll f airness i t m ay b e s aid t hat t here a re a n umber o f o perators, w ho t hrough l ack o f u nderstanding a re u nable t o g et t he b est f rom t heir i nstruments, b ut t he r esults f rom e ither o f t hese c ircumstances i s a d isappointing m icrograph. E xcluding t he s pecialised t echniques o f a nalysis a nd m etallurgy, I w ould l ike t o d well o n m ethod o f g etting t he b est f rom y our s pecimen b y o utlining s ome o f t he t echniques t hat t wenty y ears o n a v ariety o f m aterials.

h ave

b een

u sed

o ver

t he

l ast

S pecimen P reparation M ethods o f p reparation d epend u pon t he m aterial b eing e xamined, a nd t he s tate i n w hich i t i s f ound. S pecimens f rom a m arine e nvironment r equire d ifferent t reatment t o t hose f rom a t errestrial o ne. G enerally s peaking a ll s pecimens t o b e e xamined i n t he S EM s hould b e c lean a nd a bsolutely d ry. D rying c an b e a chieved b y d esiccation o ver s ilica g el w ith o r w ithout v acuum, o r s imply b y p lacing t he s pecimen i n a 3 7 C o ven t ill i t i s d ry. W et o r d amp s pecimens w ill n ot s tick t o S EM s tubs e ven w ith t he m ost s uitable a dhesives, a nd i f a dhesion i s o btained b y s ome o ther m ethod, t he m icroscope w ill n ot b e a ble t o a chieve o perating p ressure i f t here i s v apour b eing g iven o ff b y t he s pecimen. S ome m icroscopes a re a ble t o t olerate a p oorer v acuum t han o thers, b ut t he p oorer t he v acuum t he p oorer t he r esolution a nd t he w orse t he q uality o f t he m icrograph. S pecimens r ecovered f rom d amp o r w et e nvironments m ust h ence b e t reated t o r emove m oisture. A ir d rying o r d esiccation m ay c ause c onsiderable s hrinkage a nd t herefore o ne m ust c onsider a lternative m ethods. T he t wo m ost c ommonly u sed a re f reeze d rying a nd c ritical p oint d rying.

9

Freeze Drying Specimens may be washed or sieved to remove adherent material and may, depending on the durability of the specimen, be subjected to ultrasonic treatment. After this initial treatment they should be thoroughly washed in at least three changes of double glass distilled water, noting that deionised water should not be used as a substitute, for glass distilled water. After the cleaning, the material should be frozen in a minimal quantity of distilled water and placed in a previously cooled freeze drying chamber. The apparatus is · then evacuated and the drying proceeds. The rate of drying is dependent upon the physical size and the density of the specimen, it is better to leave the specimen too long in the apparatus than to take it out before the drying cycle is complete. Critical Point Drying Specimens for critical point drying are usually "fixed" in the biological sense, that is to say that they have been treated with a chemical substance, usually formalin or alcohol, to preserve them. Archaeological fixatives or consolidating substances such as polyvinyl acetate emulsion should not be used on specimens intended for SEM examination, as the presence of this substance will obscure fine detail on the surface. Specimens that do not appear to dry well with the Material for freeze drying method may be critical point dried. critical point drying is dehydrated through ascending grades of alcohol or acetone in water. The starting solution may be as low as 10%, then the specimens are transferred through the ascending grades of 20%, 30%, 40%, 50%, and so on till 100% is reached, then two changes of the absolute solvent follows, in order to ensure that all the water has been removed. If alcohol has been used to dehydrate the material it should be treated in two changes of acetone prior to the next stage. When dehydration is complete the material is placed in the critical point drying apparatus and drted. The two methods outlined above give satisfactory results, but you may find that some materials respond better to freeze drying and others to critical point drying; much depends upon the material and its state when found. It must be emphasised that material recovered from the sea must be thoroughly washed in distilled water prior to further treatment. Freeze drying rather than critical point drying appears to be more suitable for artifacts that have been recovered from the sea. Assuming that you have a clean specimen, the riext stage is to mount it on a stub, and this is where many mistakes are made. There are very few mountants that are suitable for this purpose. It is popularly assumed that any adhesive will suffice to hold the specimen onto the stub, but in fact nothing could be further from the truth, as there are very few adhesives that are stable inside the microscope. It was common practice some years ago to mount specimens on double sided adhesive tape, indeed some firms still sell stubs made up with double­ sided tape, but these should be avoided if you value your specimens or the inside of your instrument. Double-sided tape is convenient to use

b ut i nteracts w ith t he e lectron b eam t o p roduce v apours t hat d eposit o n t he f inal a pertures a s c arbon, r educing t he r esolution o f t he i nstrument. O ther d rawbacks o f d ouble-sided t ape a re t hat i t d ehydrates even outside t he m icroscope, a nd c racks, c ausing c onductivity p roblems w ith t he s pecimens. M any o ther a dhesives h ave d isadvantages: t he p opular d ags, s ilver a nd c arbon, a re n ot s uitable f or s oft o r a bsorbent s pecimens, a s t hey . tend t o c reep a nd b e a bsorbed b y t he s pecimen. E xperience h as s hown t hat

f or

g eneral

p urposes

t here

i s

n othing

t o

e qual

A raldite

f or

a ttaching s pecimens t o s tubs. T here a re t wo t ypes o f d omestic A raldite a vailable, q uick s etting a nd n ormal. T he n ormal t ype s hould b e u sed, a s t he r apid o r q uick s etting v ariety o ften d oes n ot c ompletely c ure.

t o

E xperience w ill s how t hat e ven t he s mallest s amples m ay b e f ixed a s tub w ith A raldite w ithout c reeping. W ater s oluble R esin " W",

m ade b y E vostick, a nd D urof i x, m ade b y R awlplug, a re t wo o ther s uitable a dhesives. D urofix m ay b e d iluted w ith b utyl o r e thyl a cetate o r a cetone. W hen e ither o f t hese a dhesives i s u sed i t i s n ot d ifficult t o r emove t he s pecimens f rom t he s tubs o nce t hey h ave b een e xamined .

C oating S putter c oating h as n ow r eplaced t he o nce c oating; i t i s m uch c heaper a nd m ore e fficient.

p opular

e vaporative

U ncoated Material T here i s n ow a y stem m arketed u nder t he n ame o f C FAS, w hich e nable t he e xamination o f u ncoated materials i n t he S EM. C FAS s tands for C harge F ree A nticontamination S ystem , w hich i s p robably a m isleading t itle, a s o ne w ould n ot n ecessarily a ssociate i t w ith a s ystem f or l ooking a t u ncoated m aterial a lthough i t i s. T he C FAS s ystem makes u se o f t he R obinson b ackscattered d etector w hich i s q uite d ifferent t o t he m ore c ommonly a vailable a nd c heaper d iode e quivalent. T he R obinson d etector i s n ormal s econdary d etector

a s cintillator t ype m uch t he s ame a s t he f ound i n a ll S EM 's, a nd h as a m uch g reater

s ensitivity t o backscattered e lectrons t han t he d iode d evice. W hen C FAS i s f itted t o a n S EM, t he g un i s maintained a t a h igher v acuum t han t he s pecimen c hamber. T his d ifferential i s a chieved b y u sing t he d iffusion p ump t ogether w ith t he t wo s tage r otary p ump f or t he g un a nd a s econd t wo s tage r otary p ump f or t he s pecimen c hamber, e nabling t he v acuum i n t he c hamber t o b e v aried d epending u pon t he m aterial b eing e xamined. B ecause r esidual g as

i t o r

i s p ossible t o v iew s pecimens i n a p oor v acuum, t he a ir i n t he c hamber i s a ble t o c onduct a way a ny c harge

t hat m ay b uild u p, a llowing o bservations t o b e m ade w ithout c oating a t m agnifications u p t o X 10,000 f or s ome m aterials. T his t ype o f s et-up h as b een u sed i n t he E M u nit o f t he B ritish M useum ( Natural H istory) f or t he l ast f ive y ears a nd h as p roduced t housands o f p hotographs o f b oth c oated a nd u ncoated m aterial ( Figs. 1 t o 6 ), i ncluding m inerals, b ryozoans,

o stracods,

i nsects,

p lants

1 1

a nd

a rchaeological

a rtifacts.

Captions f or Plate I A ll

s pecimens

o n

t his

monoliferum ( Milne G edgrove, S uffolk .

Fig.

1 .

Gold

p late

Edwards)

c oated

a re f rom

s econdary

f ossil t he

bryozoans,

P liocene

e lectron

i mage.

M etrarabdotos

C oralline

C rag

o f

Bar

= 3 00

m icrons.

= 1 0

microns.

P rint magnification X 15.

Fig.

2 .

Gold

c oated

s econdary

e lectron

i mage.

Bar

P rint magnification X 750.

Fig.

3 .

Gold c oated backscattered

i mage.

Bar

= 3 00

microns.

P rint

= 1 0 microns.

P rint

magnification X 15.

Fig.

4 .

G old

c oated

backscattered

i mage.

Bar

magnification X 750.

Fig.

5 .

U ncoated

C FAS

I mage.

B ar = 3 00 m icrons.

P rint magnification

6 .

U ncoated

C FAS

i mage.

B ar

P rint magnification

X 15.

Fig.

= 1 0 m icrons.

X 750. N ote

t here

i s

b etter

d etail on t he l ow power C FAS i mage i n F ig. 5 t han 3 . H owever, a t a h igher magnification t he c oated s econdary e lectron i mage i n F ig. 2 i s b etter t han t he C FAS r esult i n F ig. 6 . o n t he c oated s econdary e lectron i mage i n F ig.

19

P late 1 .

1 3

V aluable t ype s pecimens w ithout d amage.

t hat

m ay

n ot

b e

c oated

h ave

b een

e xamined

O ne o ther a dvantage o f t he R obinson d etector i s t hat i t a cts a s a n a tomic n umber d iscriminator a nd v arious p hases a re d istributed

may g ive a n i ndication o f h ow w hen l ooking a t o bjects t hat

c omposed o f m ore t han o ne t ype o f m etal o r m aterial. t o t he m icroscope w hen u sing t his t ype o f d etector

t he a re

A s imple a ddition i s a n I mage M icro

A nalysis S ystem ( IMAS) o r a s imilar a pparatus c alled a S elected P hase I maging M odule. B oth o f t hese s ystems e nable s imple q ualitative a nalysis t o b e c arried o ut o n s uitable s pecimens. I t s hould b e s tressed t hat t his o nly a pplies t o . inorganic m aterials. A t ypical e xample o f t he u se o f t he C FAS m odule i s a s f ollows. M icroscopical e xamination o f s urface t races o n b ones a nd f lints c an i ndicate i f t hey w ere f ashioned i ntentionally b y h umans f or a particular p urpose, o r i f t hey a re m erely p roducts o f n ature. I t i s i mpractical i n s ome c ases t o c oat a rtifacts p rior t o e xamination i n t he S EM a nd t his i s w here t he C FAS module c omes i nto i ts o wn. S ome h undreds o f p ieces o f b one a nd f lint h ave b een e xamined b y C ook ( 1985) a nd A ndrews a nd C ook ( 1986) i n t he S EM t o e stablish t heir a uthenticity, f or t he m ost part w ithout c oating. R esults o btained s how t hat p hotographs produced u sing t his m ethod a re o f a h igh q uality s uitable f or publication.

t he a nd

Replicas R eplicas h ave b een u sed f or e xamining m icroscopical d etail f or w ell o ver a h undred y ears. I singlass was u sed b y m ineralogists t o r eplicate t he s urface d etails o f c rystals a s f ar b ack a s 1 843 a nd b otanists w ere u sing s hellac f or making r eplicas o f l eaf s urfaces a t t he t urn o f t he c entury. S ince t hen a variety o f materials h ave b een u sed, i ncluding p laster o f P aris, p araffin w ax, e lectroplating, a nd v arious r ubber c ompounds. T he

a dvent

o f

t he

e lectron m icroscope a nd l ater t he S EM c reated a

d emand f or r eplicas w ith a m uch g reater r esolution t han w as p reviously t hought n ecessary, b ecause t hese i nstruments w ere c apable o f r esolving d etail t hat w as i mpossible t o s ee w ith t he o ptical m icroscope. T he e arly t ransmission e lectron m icroscopists d evised s ome v ery r efined r eplicating m ethods f or e xamining t he s urfaces o f materials t hat c ould n ot b e e xamined d irectly i n t he m icroscope. T hese m ethods p roduced r eplicas o f a v ery h igh r esolution, a nd e nabled t he i maging o f d etail d own t o b elow 1 0 n m . H owever f or t he g eneral u ser, t he m ethods w ere n ot a lways p ractical a s m any o f t hem i nvolved t he d estruction o f t he m aterial t hat w as b eing r eplicated. T he a dvent o f t he S EM g ave u s a m ethod o f l ooking d irectly a t s urfaces w ithout a lways n eeding t o r eplicate, b ut t he r estriction i mposed b y t he s ize o f t he c hamber o n t he s ize o f t he o bject a gain t urned u ser's m inds t owards r eplicating m aterials a nd m ethods. P fefferkorn a nd B oyde ( 1974), P ameijer ( 1978), Hamilton-Waters ( 1983) a nd B romage ( 1984) a ll e xamined v arious r eplicating m aterials w ith a v iew t o t hem b eing u sed i n t he S EM, a nd t heir f indings a nd r ecommendations a re a g ood s tarting p oint f or a ny w ork o n t his s ubject. T he e arly S EM 's w ere c apable o f a r esolution o f 2 0

n m,

w hich w as

r arely a chieved.

P resent d ay i nstruments a re c apable

1 4

of achieving a resolution of 2 run which places them in the same resolving category as a TEM, and it is necessary when making replicas to bear this in mind. The nature of the material to be replicated often dictates to some degree the type of moulding material to be used. Tough materials such as bone, flint and ceramic, can frequently withstand harsher treatment than skin, wood or plant remains. For tough, resilient materials cellulose acetate replica peels can be made simply by applying a strip or larger piece of cellulose acetate sheet, softened in acetone, to the surface to be replicated. When the acetone has evaporated, the cellulose acetate is peeled away from the specimen, and sputter coated and may then be examined in the SEM as a negative impression. High resolution images can be obtained using this method (Figs. 17 and 18) (Hill, 1986). Alternatively, a positive may be made using a silicone rubber compound such as Dow Corning 9161. Resolution to the order of 100 nm can be achieved with this material, and it appears to have a good dimensional stability. D'Errico et al. (1984), published some excellent examples of surface features on worked bone obtained using a nitrocellulose compound containing a plasticiser, with results very similar to those achieved by the acetate peel method. The advantage of both of these peel methods is that the results may be examined using transmitted light microscopy as well as scanning electron microscopy. There are a great variety of moulding compounds available at the present time. Many of these are used in dentistry for taking impressions prior to making dentures or crowns, but the degree of replication of detail required for this type of moulding is often not as great as that required for SEM investigations. Some of the dental materials are expensive and the results obtained from them are poor for high resolution work, see Figs. 7 to 16. Watson and Alvin (1976) encountered some difficulty when using Silflo, a two stage dental silicone rubber compound for reproducing details of silicified plants.. Work in our laboratory with Silflo has shown that it is not suitable for high resolution moulds as it does not reproduce detail well at a microscopical level, it tends to wrinkle, and is very prone to beam damage in the microscope. Siveter (1982) used Silcoset 105, to reproduce details of the fine o r n a m e n t a t i o n o n o s tracods and found that it fulfilled his requirements. We have also used this material with great success on a number of different types of specimens (Figs. 13 and 14), but have found that Dow Corning 9161 (Figs. 15 and 16) gave superior results, particularly when outgassed under partial vacuum before applying to the Reprosil is another silicone rubber, which gave poor specimen. resolution (Figs. 9 and 10). Wacker RTV-ME 622A&B is not suitable for this type of work as it is readily inhibited by the presence of contaminating material such as plasticine, a material commonly used in moulding processes. Xantopren Blau (light body) (Figs. 7 and 8) is a silicone rubber compound which gave average results. M-Polymer Wacker 4352 is not a silicone, but�consists of mixed polymerisates embedded into a matrix of polydimethylesiloxanes. It is a fairly rigid material when set but does not have the dimensional stability required for 15

captions for Plate 2 All specimens illustrated on this plate are spore·s or part of a spore of Qasimia, a new genus of marattialean fern from the Permian of Saudi Arabia.

Fig. 7.

Xantopren blau.

Bar

=

6 microns.

Print magnification X2500.

Fig.

Xantopren blau.

Bar

=

5 microns.

Print magnification XlOOO.

8.

Fig. 9. X2500.

Reprosil light body.

Bar

=

6 microns.

Print magnification

Fig. 10. Reprosil light body. XlOOO.

Bar

=

5 microns.

Print magnification

Fig. 11. Rubber latex.

Bar

=

6 microns.

Print magnification X2500.

Fig. 12. Rubber latex.

Bar

=

5 microns.

Print magnification XlOOO.

16

P late 2 . 1 7

Captions f or P late 3 A ll o f

s pecimens Q asimia,

i llustrated o n

a n ew g enus

t his plate

a re

s pores

o r part

o f a s pore

o f marattialean f ern f rom t he P ermian o f S audi

Arabia. Fig.

1 3.

I .C.I.

S ilcoset.

Bar = 6 microns.

P rint magnification X 2500.

Fig.

1 4.

I .C.I.

S ilcoset.

Bar = 5 microns.

P rint magnification X 1000.

Fig.

1 5.

D ow

C orning

9 161.

B ar

= 6 microns.

P rint

magnification

1 6.

Dow

C orning

9 161.

B ar

= 5 m icrons.

P rint

magnification

X 2500.

Fig. X 1000.

Fig.

1 7.

C ellulose a cetate peel.

Bar = 6 microns.

P rint magnification

C ellulose a cetate peel.

B ar = 5 microns.

P rint magnification

X 2500.

Fig.

1 8.

X 1000.

1 8

P late 3 .

1 9

m icroscopical w ork. I w ould s tress t hat t here a re l iterally d ozens o f p roprietary s ilicone r ubber m oulding c ompounds b ut v ery f ew o f t hem a re s uitable f or r eproducing m icroscopical d etail. a vailable m aterial t hat h as b een t ried i s r ubber

A nother c ommonly l atex ( Figs. 1 1 a nd

1 2) p robably t he c heapest a nd e asiest o f a ll m oulding c ompounds t o u se. I t i s m ade u p i n a n a mmonia b ased s olution a nd c an b e a pplied i n v ery t hin l ayers w hich c an b e b uilt u p a nd r einforced. T he r esulting m oulds g ive p oor r esolution b ut a re s table i n t he m icroscope. W hen u sing t his t ype o f l atex i t c an b e p ushed i nto t he s pecimen w ith a f ine j et o f c ompressed a ir f rom a " dust o ff" c an o r a c ompressor. I t i s s uggested t hat D ow C orning 9 161 b e u sed w ith c atalyst 9 162 f or m oulding m aterials t hat a re t oo d elicate t o b e t reated b y t he p eel m ethod. T he m oulding c ompound c an b e b lown i nto t he s urface w ith c ompressed a ir o r a pplied u nder v acuum a nd w hen t he m aterial h as s et i t c an b e p eeled o ff t he s pecimen. M oulds m ay b e f ixed t o s tubs a nd c oated b ut i f t his i s p roposed a s mall p iece o f f ilter p aper s hould b e e mbedded i nto t he b ack o f t he r ubber b efore i t s ets t o e nable t he m ould t o b e a ttached t o t he s tub, a s i t i s v ery d ifficult t o s tick s ilicone r ubber c ompounds t o m etal. M oulds n ormally h ave t o b e c oated b efore t hey a re v iewed i n t he S EM, b ut i f o ne i s u sing a C FAS a pparatus t hey c an b e v iewed u ncoated . I f

positive

c asts

a re

r equired

t hey

m ay

b e

m ade

w ith

A raldite,

h owever t his m aterial f requently c harges i n t he m icroscope e ven a fter c oating, a nd i t i s a dvisable t o m ix a l ittle powdered g raphite w ith i t b efore making t he c ast t o e liminate a ny c harging p roblems. Appendix R obinson b ackscattered d etector

i s p art o f

t he

C FAS

s ystem b ut

i t m ay

b e u sed i ndependently o f t he s ystem . I t i s a h igh g ain d etector, a nd i t a nd t he S elected P hase I maging M odule s ystem a re a vailable f rom, E xpo Sem L td., M oat F arm, C hurch R oad, M ilden, I pswich, I P7 7 AF, E ngland. I MAS: I mage a nd M icro A nalysis S ystem i s a vailable f rom C ambridge T echnology, C hesterton M ill, F rench's R oad, C ambridge C B4 3 NP, E ngland. S olid S tate D iode D etector i s a vailable f rom K .E. D evelopments L td., T he M ount, T oft, C ambridge, C B3 7 RL, E ngland. T his particular d etector i s v ery g ood f or backscattered w ork. I t i s d ivided i nto f our q uadrants a nd e ach c an b e u sed i ndependently i n e ither p olarity a llowing s um a nd d ifference s tudies t o b e m ade. A cknowledgements T he a uthor i s i ndebted t o, a nd w ishes t o p lace o n r ecord, h is a ppreciation o f t he i nterest t aken i n t his p aper b y D r. C .R. H ill a nd f or h is p ermission t o u se F igs. 7 t o 1 8. T hanks a re a lso d ue t o D r. P .D. T aylor f or t he u se o f F igs. 1 t o 6 , a nd t o t he p hotographic s taff, a nd m embers o f t he P alaeontological l aboratory o f t he B ritish M useum ( Natural H istory).

2 0

R eferences A ndrews,

P .

a nd

C ook,

t emperate s etting. B romage,

T .G.

J .

1 985.

M an 2 0:

1 985.

J .

1 985.

T he

J ournal o f M icroscopy 1 37:

a pplication

o f

s canning

t aphonomic a nd a rchaeological problems. t he

U pper

t o

b ones

i n

a

S ystematic i nquiry i n t ests o f n egative/positive

r eplica c ombinations f or S EM. C ook,

N atural modification

6 75-691.

P alaeolithic

o f

B ritain

I n R oe,

a nd

2 09-216.

e lectron microscopy D .A .

N orthwest

( ed.),

t o

S tudies i n

E urope.

Oxford,

B ritish A rchaeological R eports. D 'Errico,

F .,

G iacobini,

G .

a nd P uech,

P .F.

1 984.

n ew m ethod f or s tudying worked bone s urfaces. H amilton-Waters, materials

a nd

P .

1 985.

t echniques

A i n

r eview

u se

B ritish M useum ( Natural H istory). H ill, i n

C .R.

f ossil

1 986.

t axonomy.

a nd

T axonomic

C .H.

1 978.

m icroscopy-a r eview. P fefferkorn,

G .

I n

D .J .

J .

a nd

c asting

l aboratory,

3 7-43.

R .A . i n

a nd A lvin,

a nd

T homas,

B .A.

P alaeobotany.

A .

C asts

K .L.

( eds.),

S ystematics

1 23-136.

R eplica

a nd Boyde,

1 982.

S picer,

t echniques

f or

s canning

1 974.

e lectron

8 31-836.

R eview o f r eplica t echniques f or

S canning E lectron M icroscopy part

i llustrating

o stracod. I n B ate, R .H., R obinson, E . F ossil a nd R ecent O stracods, pp. 1 05-122. L td. W atson,

moulding

S canning E lectron M icroscopy part 2 :

s canning e lectron m icroscopy. 8 2. S iveter,

t he

palaeontology

T he C onservator 7 :

A pproaches

A ssociation S pecial Volume 3 1: P ameijer,

o f t he

a

2 9-51.

T he e pidermis/cuticle a nd i n s itu s pores a nd pollen

p lant

S ystematic

a t

Varnish r eplicas,

O SSA 9 -11:

1 976.

f ine

o rnament

o f

1 :

7 5-

a S ilurian

a nd S heppard, L .M . ( eds.), C hicester: E llis a nd Horwood

S ilicone r ubber c asts o f s ilicified

p lants f rom t he C retaceous o f S udan.

2 1

P alaeontology 1 9:

6 41-650.

RACKSCATTERED E LECTRON I MAGING O F ARCHAEOLOGICAL MATERIAL N igel M eeks I ntroduction B ackscattered e lectron ( BSE) i maging i n t he s canning microscope h as g ained s tature i n r ecent y ears b ecause

e lectron o f t he

availability o f m ore e fficient d etectors t hat c an e xploit t he c ompositional o r a tomic n umber c ontrast b etween c losely s imilar p hases i n p olished s amples. T he c ompositional c ontrast i ncreases a nd c larifies t he i nformation a vailable f rom a s ample a nd t herefore s peeds i nterpretation, a s w ell a s d eepening t he k nowledge o btained f rom e xamining t he m aterial. A n a dditional b enefit o f B SE i s t he s uppression o f s pecimen c harging i n t he S EM t hat o ccurs w ith s econdary e lectron i mages, f or e xample o n t he s urface o f a ntiquities d ue t o c orrosion a nd b urial d ebris, a nd o n s amples t hat a re d ifficult t o vacuum c oat, b ut c harging i s g enerally a bsent i n B SE i mages. T opographic i nformation i s a lso o f i mportance i n t he B SE s ignal c oming f rom t he s pecimen. H owever, t he t ype o f i mage o btained, w hether c ompositional, t opographic o r m ixed d epends n ot o nly o n t he p repared c ondition o f t he s ample ( eg p olished, e tched, f ractured, e tc.), b ut a lso o n t he c hoice o f S EM a ccelerating v oltage a nd p robe c urrent, w hich can be particularly important f or c eramic m aterials. T he d etector/specimen g eometry a lso h as a n i mportant e ffect o n t he t ype o f i mage a s d oes t he s ize a nd d esign o f t he B SE d etector t o s ome e xtent. T herefore, d etectors m ounted w ith d ifferent g eometries a nd w orking d istances g ive i mages w ith d ifferent c ontributions o f c ompositional a nd t opographic c ontrasts. o r s uppressed.

" Edge b right-up"

e ffects m ay a lso b e

e nhanced

T he p urpose o f t his p aper i s t o i llustrate w hat h as b een f ound t o b e t he b est B SE i maging c onditions f or a v ariety o f a rchaeological m aterials.

D etector G eometries T he S EM u sed f or t he w ork i n t his paper i s a J EOL 8 40 w ith t hree p urpose-designed b ackscattered e lectron d etectors, t he g eometries o f w hich a re i llustrated i n F ig. 1 . D etector ' A ' i s a s plit s olid-state a nnular d evice m ounted o n t he f inal l ens a nd c lose t o t he e lectron b eam a xis a t a w orking d istance o f 3 9 mm f rom t he s ample ( JEOL, 1 980). T his d etector i s t echnically i n t he i deal p osition t o g ive maximum a tomic n umber c ontrast, b eing l ocated w ithin a 4 0- c one r egion a bove t he s ample ( Fig. 2 ). I n p ractice, h owever, i t i s r ather s mall i n s urface a rea f or s imilar,

t he b ut

s tandard l ong w orking d istance. D etector ' B ' i s a l arger d iameter s olid-state d evice m ounted o n t he

r etractable o ptical m icroscope a rm . I n i ts n ormal p osition i t h as a w orking d istance o f 4 mm a bove t he s ample. I n p ractice, t his w orking d istance i s t oo c lose, a s t he d etector e lements a re o utside o f t he 4 0 c one

r egion

a nd,

a s

a

c onsequence,

t he

c ompositional

c ontrast

i s

r educed a nd " edge b right-up" e ffects a re e nhanced. M oving t he s ample s tage d own t o g ive 1 3 m m w orking d istance c ures t he p roblem a nd t he d etector i s t hen w ell p ositioned f or g ood c ompositional c ontrast a nd l ow n oise. I n t his p osition t he d etector h as a s ignificant s ignal t o

2 3

Fig.

1 .

D iagram

of

t he

J EOL

8 40

geometries.

2 4

backscattered

e lectron

d etector

E 5 -40kV

F ig. 2 . D iagram t ake-off a ngles.

i llustrating

t he

2 5

t ype

o f

i mage s een

a t v arious

B SE

noise and contrast advantage over the small detector 'A' . The third BSE detector, 'C' , is a retractable, large surface area scintillator device (Robinson type design). but which for technical reasons has an odd geometry. It is inclined 12° from the horizontal, and because the active area is asymmetrical about the electron beam axis and because of its large size it crosses the boundary between the compositional contrast and the topography regions and collects BSE over a 100° wide cone angle. Consequently, this device always makes a topographic contribution to the compositional image. The detector can be retracted out of the electron beam axis into a position where it is excellent for topographic imaging. This device also works at 'TV' rate with low probe currents in contrast to the solid-state detectors which require excessive probe currents in this mode due to signal loss in the amplifier. However, under normal probe current conditions and at slow­ scan rates the solid-state detectors can given excellent compositional images free from topography and "edge bright-up" effects. Compositional Contrast There are two fundamental properties of the backscattered electron radiation from the surface of a polished sample. The first property is the dependence of the BSE yield on the mean atomic number of the phases present (Fig. 3), which results in the higher mean atomic number phases appearing as brighter areas of the resulting image (Goldstein, 1981; Reed, 1975). Differences in atomic number of about 0.1 are claimed to be observable (White, 1984), and our system has been able to image a difference of 0. 9 between two intermetallic compounds of copper/tin. The contrast between these two phases was difficult to observe in the unetched condition due to much higher contrast from adjacent areas of However, the chemical the metal sample (Hall and Lloyd, 1981). compositions of these two compounds were very easily distinguished by EDX analysis ( E: phase 38.2% Sn and o phase 32. 6% Sn), and they were also distinguished by colour contrast in the optical microscope. This raises the need for a cautionary note that compositional imaging will not always clearly show phase differences that are present, and in practice they may be mar� obvious by optical microscopy and EDX analysis. However, etching does reveal phase boundaries that can be easily seen by topographic imaging in the SEM. The second fundamental property of the backscattered electron radiation from the surface of a polished sample is that the contributions of compositional contrast and topographic contrast in the signal vary with the BSE take-off angle. This important property is often overlooked in publications but it plays an important role in the resulting image. The compositional contrast increases to a maximum as the take-off angle approaches the vertical at which point the topographic contrast is very low, and conversely the topographic contrast increases at low take-off angles where the compositional contrast is very low. The distribution of the backscattered electrons from the sample and hence the type of image seen at various detector geometries is illustrated in Fig. 2. A dramatic demonstration of the change in compositional contrast and topographic contrast with BSE take-off angle is shown in Figs. 4 and 5. The glass spherule from the combustion of a 14C charcoal sample

26

A u P b i l

A gS n 44

C u F e 4 C a l S i N a 4 4

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

Dependence o f b acksca t ter ing c oe f i c ien t /o n a tom ic n umber Z f o r E , = t o-3o k eV ( a f ter B ishop , 1 966a ) .

F ig. 3 . D iagram i llustrating t he r elationship o f e lectron y ield t o t he a tomic n umber o f t he e lements.

2 7

t he

b ackscattered

Fig. 4 . Glass s pherule s howing t he t opographic B SE t he r etracted s cintillator d etector ( C).

Fig.

5 .

G lass

s pherule

t he s olid-state d etector

i mage

t aken w ith

s howing t he c ompositional B SE i mage taken w ith ( B)

d irectly a bove t he s ample.

2 8

s hown i n F ig. 4 w as t aken w ith t he r etracted s cintillator d etector ' C ' ( shown i n F ig. 1 ) a nd t he i mage w as d ominated b y t opographic i nformation, b ut a l ittle c ompositional c ontrast w as a lso s een. F or c omparison, F ig. 5 w as t aken w ith t he s olid-state d etector ' B ' d irectly a bove t he s ame s ample a t 1 3 mm w orking d istance a nd c learly s hows t he c ompositional v ariation o f t he c alcareous c onvection l ines i n t he o nce m olten g lass.

T herefore,

t o o btain maximum a tomic n umber c ontrast f rom

a s ample, t he d etector m ust b e p laced h orizontally a nd s ymmetrically a bove t he s ample a nd c lose t o t he e lectron o ptical a xis. I t s hould c ertainly b e w ithin a c one o f a bout 4 0- f rom t he p oint o f f ocus o n t he s ample, w hich i s f ound t o b e t he r egion o f maximum c ompositional c ontrast ( Fig. 2 ). A d etector ( such a s ' A ') m ounted i n t his p osition w ill e ffectively f latten t he i mage a nd g ive a ' clinical' v iew o f t he compositional c ontrast f ree f rom " edge b right-up" e ffects a nd t opography. C onversely, o utside o f t his 4 0 c one r egion t he s ubtle c ompositional c ontrast e ffects r educe d ue t o i ncreased B SE i nteractions i n t he s ample t hat o ccur a t l ower t ake-off a ngles. H owever, t hese l owa ngle B SE g ive g ood t opography a nd e dge c ontrast d ue t o t he l ine-ofs ight t rajectories. F or h igh c ontrast a nd l ow n oise c omposition i mages, t he d etector s hould b e r easonably c lose t o t he s ample, p rovided t hat t he d etector e lements r emain w ithin t he 4 0 c one r egion. H owever, i f t he d etector i s t oo c lose a nd t he d etector e lements a re o utside o f t he 4 0 c one r egion t heir c ompositional c ontrast r educes a nd " edge b right-up" e ffects d ominate. T his i s p articularly n oticeable o n p olished c eramics w hich h ave m icrotopography a nd p orosity, y et f or d eep-etched m etal s amples t his e ffect c an b e u nexpectedly a dvantageous. T he c eramic s ample s hown i n F ig.

6w hich d emonstrates t he " edge b right-

u p" e ffect a nd l oss o f c ompositional c ontrast w as t aken w ith d etector ' B' a t 4 mm w orking d istance, a nd w as t herefore t oo c lose t o t he s ample. T he s ame a rea i s s hown i n F ig. 7 b ut t aken a t 1 3 m m w orking d istance w ith t he s ame d etector. T his d ramatically s hows t he m uch i ncreased c ompositional t he c orrect d istance e liminated. T he

S EM

i nformation t hat t he i s u sed a nd " edge

a ccelerating

v oltage

h as

a n

s ample h as t o o ffer w hen b right-up" e ffects a re

e ffect

o n

t he

i mage d ue t o

b eam p enetration, a lthough t he b ackscattering c oefficient d oes n ot s ignificantly c hange. F or c ompositional c ontrast, m etal s amples n ormally b enefit f rom h igher k V s ettings, e g 2 0 k V u pwards, w hile c eramics a nd g lassy m aterial b enefit f rom l ower v alues i n t he r egion o f 1 5 k V w hich r educes b eam p enetration a nd " edge e ffects" t hat w ould o therwise r educe t he c ompositional c ontrast. L ower v alues d own t o 5k V c an b e u sed t o s how s ubtle p hase c ontrasts i n s ome c eramics, b ut r esolution b egins t o f all. I n m etals, c rystallographic g rain o rientation o r e lectron c hannelling c ontrast c an a lso b e s een m ore c learly a t r educed k V ( between 8 -15 k V), a gain r educing b eam p enetration a nd a llowing o nly t he s urface c rystals t o a ffect t he b ackscattered ( and a bsorbed) e lectron y ield ( Joy, 1 973; N ewbury, 1 974; W ells, 1 974; S chur, 1 974).

T opographic C ontrast T opographic i maging i s a chieved i n f our w ays. I n t he f irst t he s plit a nnular d etector ( 'A ' o r ' B' i n F ig. 1 ) m ounted d irectly a bove t he s ample i s s witched t o t he t opography m ode ( ie, t he s ignals f rom t he t wo

2 9

F ig. 6 . C eramic s ample c ompositional c ontrast w hen s ample.

F ig.

7 .

T he

c ompositional

s ame

c eramic

c ontrast

w hen

s howing ' edge b right-up ' a nd l oss o f t he B SE d etector ( B) i s t oo c lose t o t he

s ample t he

B SE

w orking d istance.

3 0

a s

F ig.

d etector

6 b ut ( B)

s howing i s

a t

t he

d etailed c orrect

d etector

e lements

a re

s ubtracted)

b ut

t his

g ives

a r ather

a rtificial

t ype o f i mage t hat m ay a lso l ose i mportant d etail. S econdly, i t i s m uch b etter t o m ove t he d etector ( 'B' o r ' C ') o ff-axis, o ut o f t he 4 0" c one r egion a nd u se i t i n t he c omposition m ode ( je, s ummation o f t he t wo d etector e lement s ignals) f or l ine-of-sight B SE d etection. I n t his c ase t he c ontrast i s m uch b etter a nd d etail i s e nhanced o ver t he f irst m ethod. T hirdly, t he s econdary e lectron c ollector h igh v oltage ( HV) c an b e t urned o ff f or a s imilar, b ut m ore n oisy i mage t han t he o ff-axis B SE d etector, a nd f ourthly a nd m ore u nusually, c ertain o bjects o r s amples s een a t l ow m agnification m ay h ave a s triking t hree-dimensional i mage w hen v iewed f rom d irectly a bove i n t he c ompositional m ode. I n t his w ay t he s ample i s s een w ith a u niform ' illumination', a s ituation w hich i s p articularly t rue o f g old c oated s amples v iewed a t a l ong w orking d istance. T opographic B SE i maging h as r ather m ore a pplications t han i s p erhaps g enerally r ealised, a nd i n p ractice a n i ncreased b eam c urrent w hich r educes n oise, o ften h elps t o s how t his p otential.

S ample P reparation R esin

m ounted

p olished

s ections

a nd

g lass

m ounted

t hin

s ections

a re p repared i n t he n ormal w ay f or o ptical m icroscopy; t he b etter t he p olish t he b etter t he r esults a re f or b oth t echniques. S EM e xamination o f m etals b y B SE b efore e tching i s a n a dvantage i n t hat t he s ubtleties b etween p hases, d iffusion z ones a nd c oring a re v isible, a nd i s e ssential f or E DX a nalysis i n o rder t o e nsure t hat n o m etals h ave b een d issolved f rom t he s urface. E tching c an f ollow c ompositional B SE i maging a nd E DX a nalysis. I t i s o ften b est i f d eeper e tching t han f or n ormal o ptical m icroscopy i s u sed f or S EM e xamination i n o rder t o e nhance g rain b oundary d etail. C arbon c oating i s u sed f or a ll p olished s amples

i n

r esin

m ounts,

b ecause

t he

c ompositional

c ontrast

c learly

s hows t hrough t he c arbon c oat. S ome t hree d imensional s amples f or t opographic i maging, f or e xample s ilicone r ubber m oulds, c an b e g old c oated t o i ncrease t he B SE y ield. G old c oating e ffectively s uppresses a tomic n umber c ontrast f rom t he s ample b ut e nhances t opography. T apered s ections a re polished t hrough t he s urface l ayers o f s ome a rchaeological o bjects i f s amples c annot b e t aken. W ith t apered s ections, t he o bject i s p olished a t a l ow a ngle t o t he s urface, o ften o n a c onvex e dge. T he s urfaces o f u ncleaned c orroded o bjects c an b e s uccessfully e xamined b y B SE t echniques b ecause c harging e ffects a re s uppressed.

Examples o f A rchaeological Material Viewed by B ackscattered E lectrons T o

i llustrate

t he

a rchaeological m aterial,

r ange

o f

e xamples

o ptions

a vailable

a re g iven

f or B SE

i maging o f

f or a v ariety o f m aterials

t hat h ave b een r ecently e xamined. M etals.

A n u nprepared b ronze F rankish s trap-end o f t he 5 th c entury A D

i s s een a t l ow m agnification i n t he B SE c ompositional m ode i n F ig. 8 . T he s urface o f t he o bject c learly s hows t he d eep d ecorative p attern, b ut i n a ddition d isplays a reas o f w ear t hrough t he l ight-coloured

3 1

F ig.

8 .

T he u nprepared

s urface o f

a F rankish

s trap-end

s hown

i n t he

c omposition m ode.

F ig.

9 .

D etail o f

t he w orn

s urface o f

t he

F rankish s trap-end s howing

t he d endritic c ore m etal a nd t he t wo i ntermetallic c ompound l ayers a nd e psilon) o f t he t inned s urface.

3 2

( eta

s urface l ayers t o t he c ore m etal b elow. T hese a reas o f w ear f orm n atural t apered s ections t hrough t he s urface l ayers. F ine d endrites o f t he c ast m etal c an b e s een i n t hese a reas. F ig. 9 s hows a v iew a t h igher m agnification, i n w hich t he d endrites a re s een t o b e t otally c orroded, b ut s till r etain t heir o riginal c ored s tructure. T he l ow-tin p rimary d endrites a re d ark a nd t he h igher-tin o uter d endrite l ayers a re l ight. A dditionally, a + 6 e utectoid i slands a re s een i n t he i nterdendritic h igh-tin regions. T hus a c lassical b ronze microstructure i s clearly s hown o n a n u nprepared o bject b y c ompositional B SE i maging. T he t wo l ight s urface l ayers i n F ig. 9 ( at t he e dges o f t he w orn t apered s ection) a ppear a s t wo d istinct g rey l evels w hich, w hen a nalysed, w ere f ound t o b e t he c ompositions o f t he i ntermetallic c ompounds n a nd E . T hese l ayers a re t ypical o f a b ronze t hat h as b een t in p lated b y m elting t in o nto t he s urface o f t he b ronze. T apered

s ections

o f,

o r

s amples

f rom

m etal

o bjects

o ften

s how

g reat d etail i n p olished, b ut u netched, s ection w hen v iewed b y c ompositional c ontrast. I n t he f orged c oin o f s ilver-clad c opper a lloy s hown i n F ig. 1 0, s etting t he B SE c ontrast t o g ive a f ull r ange o f g rey l evels e mphasizes t he l ayered s tructure o f t he c oin. T he r esin m ount h as l ow B SE y ield a nd i s t herefore b lacked o ut, w hile t he t hree-layered s tructure o f t he c oin i s c learly s een. T he w hite o uter l ayer c onsists o f s ilver o verlying a g rey i ntermediate b ody m etal. T he b ody m etal h as l ight

l ayer s pots

a nd a d ark c opper a lloy s howing t he p resence o f

s mall l ead g lobules, a nd b lack c orroded a reas a nd r esidual c oring a re a lso v isible. A s econd'micrograph a t h igher m agnification ( Fig. 1 1) i s s hown w ith e xpanded c ontrast t hat h as b lacked o ut b oth t he p lastic m ount a nd t he c opper c ore. T his e xaggerates t he c ontrast b etween t he t wo s urface l ayers a nd s hows t he l ight s ilver s urface l ayer c learly b onded t o t he s ilver/copper e utectic s older r egion w hich j oins t he s ilver t o t he c opper c ore. E tched m etals c an s how t heir s tructure v ery c learly b ut t he i mage t ype d epends o n w here t he d etector i s p laced. T he d eep e tched h igh-tin b ronze s hown i n F ig. 1 2 i s a nnular s plit d etector ( 'A ')

t aken i n t he c omposition m ode w ith m ounted a t 3 9 mm a bove t he s ample.

t he T he

e tched s tructure s hows n o t opography a t t he g rain b oundaries, b ut c learly s hows t he l ighter, h igh-tin a+ 5 e utectoid r egions a djacent t o t he d arker, c ored, l ow-tin b ronze a p hase. C asting p orosity i s s een a s d ark a reas d ue t o t he l ow B SE y ield f rom t hese r egions, a lthough t he l arge p ores d o s how s ome d etail w ithin. A lso n ote t hat s everal t iny g lobules o f l ead a re d istributed t hroughout t he s ample a nd s how u p a s w hite s pots. v iewed b y t he

C ompare t his w ith t he s ame a rea i n F ig. 1 3 w hich i s l arger d iameter a nnular d etector ( 'B ') a t 4 mm w orking

d istances, w ith t he d etector e lements w ell o utside o f t he 4 0" ' c one r egion. I n t his c ase t he i mage i s v ery c learly t opographic a lthough t he

d etector

i s

s witched

t o

t he

c ompositional

m ode

y et

r etains

s ome

c ompositional i nformation. T he t opography i s e mphasised b y t he b right e dge e ffects o n t he e utectoid a djacent t o i ts o wn s hadow w hich i s c ast o n t he b ronze. N ote a lso h ow t he d etail i s l ost i n t he p orosity d ue t o t he l ow a ngle o f t he B SE, p roducing t he s hadow e ffect i n t he h oles. A dditionally, t he l ead g lobules a re n ow i nvisible d ue t o t he b right-up" a nd r eduction o f a vailable a tomic n umber c ontrast.

" edge M uch

d etail i s v isible i n t he b ronze b ody m etal i n t his i mage. F igure 1 4 s hows t he s ame s ample t aken w ith t he l arge s cintillator d etector ( 'C ')

3 3

F ig. 1 0. F orged s ilver-clad c oin s howing t he d ark c ore m etal, l ight s urface s ilver l ayer a nd t he m id-grey f usion z one b etween.

F ig. 1 1. D etail o f t he e utectic s older m icrostructure l ight s ilver l ayer a nd t he d ark c opper a lloy c ore.

3 4

b etween

t he

t he

F ig.

1 2.

H igh-tin

b ronze

d istance, d etector ' A '. g lobules c an b e s een.

T he

i n

t he

c omposition

m ode

a t

e tched s ample a ppears f lat,

F ig. 1 3. H igh-tin b ronze i n t he c omposition d istance, d etector ' B'. N ote t he t opographic f ine d etail i n t he e tched b ody m etal.

m ode t ype

a t o f

l ong

w orking

a nd t iny l ead

s hort w orking i mage a nd t he

F ig. 1 4. H igh-tin b ronze t aken w ith t he l arge a rea s cintillator d etector i n t he c omposition m ode. N ote t he m ixed t opographic a nd c ompositional i nformation i n t he i mage.

3 5

d irectly a bove t he s ample a nd i s c learly a c ombination o f a tomic n umber c ontrast a nd t opography. T he c ombination o f a tomic n umber c ontrast a nd g rain o rientation o r e lectron c hannelling c ontrast i s s hown i n F ig. 1 5, t aken w ith d etector ' B ' a t 1 3 m m w orking d istance. I n t his p olished c ross-section o f a B ronze-Age s piral g old t orc f rom S hropshire t he f our a rms c learly s how t he p atchwork o f l arge a nnealed g rains. T he e nds o f t he a rms a re b urred o ver a nd t he g old g rains a re v ery s mall, i ndicating t hat a l ot o f c old w orking w as f ollowed b y a nnealing t o s often t he p repared r od b efore c oiling t he t orc. T his t extural d etail i n t he i mage i s p urely t he e ffect o f g rain o rientation c ontrast, a s t he g old i s a h omogeneous a lloy ( Au 8 0.3%, A g 1 6.2%, C u 3 .5%). I n t wo r egions b etween t he a rms, h owever, t here i s a s older i nf i ll o f t he f ollowing c omposition: A u 7 7.6%, A g 1 3.9%, C u 8 .5%. T he s older h as a l ower m ean a tomic n umber t han t he g old t orc m etal a nd i s t herefore d arker. T he s older r egion s hows a d endritic s tructure w ith g rain o rientation c ontrast a nd c oring s uperimposed. H igher magnification o f o ne a rm w ith a s oldered r egion i s s hown i n F ig. 1 6. T he d iffusion z one b etween t he g old a nd s older i s v isible d ue t o a tomic n umber o r c ompositional c ontrast, w hile t he g rains o f t he t orc a ppear b y m eans o f g rain o rientation c ontrast, r evealing t he g rowth o f g rains a cross t he c ompositional b oundary. ( A s imilar i mage i s o btained f rom t he s pecimen c urrent s ignal, b ut t his t echnique i s n ot d iscussed i n t he p aper.) N iello o f t he t ernary m etal s ulphide t ype h as a d istinctive m icrostructure t hat s hows c learly i n B SE c ompositional i maging a nd c an b e o bserved i n s itu o n f avourable o bjects i f n o s ample c an b e t aken. T he t ernary c opper/silver/lead s ulphide n iello s hown i n F ig. 1 7 i s a n e xperimentally p repared s ample t hat s hows t he l ight d endrites o f l ead s ulphide, t he s ilver/copper s ulphide e utectic f orming t he m atrix, a nd t he d ark s treaks o f c ovellite, C uS. C eramics a nd g lass. T here i s a n e normous r ange o f a rchaeological m aterial c omposed o f s ilica-based o r m ineral t ype m atrices t hat c an b e v ery e ffectively v iewed i n p olished s ection b y c ompositional c ontrast. T hese i nclude c eramics, g lass, s lag, a nd r efractory m aterials, f aience, E gyptian b lue, n atural m inerals a nd c orrosion p roducts. V itrification a nd d iffusion z ones w ithin t hese m aterials c an b e c learly o bserved a s w ell a s t he m ineral p hases t hat a re f used i n t he m atrices. T he B SE t echniques o ften c omplement t ransmitted l ight p etrographic a nalysis o f t hin-sectioned m aterial, a nd t he s ame s amples a re n ormally e xamined i n t he S EM a fter c arbon c oating. T he m atrices a re o ften v ery c omplex, b ut c ompositional c ontrast i maging p resents t he c omponent p hases i n a c lear a nd d etailed manner. A dditionally, t he ' edge e ffects' a nd b eam p enetration e ffects a re e liminated, a long w ith t he m icro-topography t hat o ften a ccompanies t hese p olished m aterials. I t i s f ound t hat f or t he b est c ompositional i nformation t he s ample s hould b e v iewed a t a r elatively l ong w orking d istance t o e nsure t hat t he d etector i s w ell w ithin t he 4 0- c one r egion, t hereby m inimising t he ' edge e ffects' a nd maximising a tomic n umber c ontrast. L ower a ccelerating v oltage o f a round 1 5 k V l imits b eam p enetration, e nhancing r esolution. T heoretically, t here i s m ore c ontrast b etween t he p hases i n t his t ype o f matrix a t l ower a ccelerating v oltages, e ven a s l ow a s 5 k V i n s ome c ases. T he p robe c urrent ( ie s pot s ize) s hould b e l arge

3 6

F ig. 1 5. G rain o rientation c ontrast s een i n t he g old t orc s ection. S older i nf i ll i s s een i n t wo a reas b etween t he a rms o n t he r ight.

F ig. 1 6. D etail o f o ne o f t he t orc a rms s howing t he g rain o rientation c ontrast w hich r eveals f ine g rains i n t he h eavily w orked e nd r egion. C ompositional c ontrast i s s een b etween t he s older a nd g old a rm , a nd a s d endritic c oring i n t he s older.

3 7

Fig. a re

1 7. s een

T ernary i n

s ulphide

t he matrix o f

s treaks a re c ovellite,

F ig.

1 8 .

n iello. e utectic

P rimary d endrites o f l ead s ulphide c opper/silver

s ulphide.

T he b lack

C uS.

C eramic s ample s hown i n s plit i mage:S - s econdary e lectron i mage s howing g ross c harging e ffects R = s cintillator d etector

( C)

B SE i mage s howing m ixed

c omposition/topography i mage L = s olid-state d etector

( A)

c ompositional c ontrast.

3 8

B SE i mage s howing t he b est

e nough t o maximise c ontrast a nd m inimise n oise, b ut n ot l arge e nough t o a ffect r esolution. U nder t hese c onditions, c lear a nd d etailed i mages a re o btained a t b oth l ow a nd h igh m agnification i mages o f t he m ineral d istribution o f c eramics a nd o f t he v itrification s tructures a cross f urnace f ragments. F igure 1 8 s hows a t ypical p olished c eramic s ample f rom a w ell v itrified c rucible f ragment. T he m icrograph s hows t hree d ifferent i mages r ecorded s equentially b y s witching t o d ifferent d etectors. T he t op ( marked S ) i s a s econdary e lectron i mage w hich d emonstrates t he p roblems o f l ow p hase c ontrast a nd s evere c harging i n t he p orosity . T he c entre ( marked R ) i s a b ackscattered e lectron I mage u sing t he l arge s urface

a rea

s cintillator d etector

( 'C')

a bove t he s ample.

T his s hows

s ome i mprovement i n a tomic n umber c ontrast, b ut t opography i s a n oticeable f eature, d ue t o t he o dd d etector g eometry d iscussed a bove. T he b ottom ( marked L ) i s t aken u sing t he s mall a nnular s olid-state d etector ( 'A ') m ounted d irectly a bove t he s ample o n t he f inal l ens o f t he S EM. I t i s i deally p laced, b eing b oth s ymmetrically a round, a nd v ery c lose t o t he e lectron a xis. N ote b oth t he d ramatic i ncrease i n t he c ompositional

i nformation b etween

t he q uartz g rains a nd t he g lassy

m atrix, a nd t he v ery f ine a nd s ubtle i nformation w hich i s s een w ithin t he g lassy m atrix. A r ound g lobule o f i ron s ulphide i s v isible a s a s mall w hite b lob o n t he l eft. A lso, a s ubtle g radation i s s een i n t he g lassy matrix f rom s lightly l ighter o n t he l eft t o s lightly d arker o n t he r ight d ue t o t he p resence o f a h igher 1 (20 c oncentration o n t he l eft. I n t he l ower i mage ( L) t here i s n o t opographic i nformation o r ' edge e ffects', b ut r ather j ust a c lean p resentation o f t he s tructure. F igures 1 9 a nd 2 0 a re l ow m agnification m icrographs o f t he s ection t hrough a f urnace l ining, f rom R io T into i n S pain, t aken u sing t he s olid-state d etector ( 'B') a t 1 3 mm a bove t he s ample t o g ive i ncreased s ignal a nd l ow n oise, c ompared t o t he s maller d etector ' A ' a t l onger w orking d istance. F igure 1 9 s hows t he f ine s tructure o f t he l ow-fired o uter s urface o f t he w all w ith q uartz a nd c rushed s lag u sed a s g rog. F igure 2 0 s hows t he h ighly v itrified i nner s urface o f t he w all o f t he f urnace, d iffusion z ones o f g lassy m aterial, a nd l ead-rich g lass h aving b een i ncorporated i nto t he p urface l ayers. T his c ompositional c ontrast t echnique i s n ow u sed b y u s a lmost e xclusively t o i mage p olished s ections o f c eramics a nd g lassy m aterials i n t he S EM . O ther

m aterials.

S ilicone

r ubber

m oulds

t aken

f rom

t he

s urface

o f

a ntiquities t o d emonstrate t ooling c an b e e ffectively i maged b y B SE m ethods. T he m ould s hown i n F ig. 2 1 i s t aken f rom a d rilled e dge o n a c ast b ronze f igure o n o ne o f t he b ronze B asse-Yutz f lagons i n t he B ritish M useum a nd w as c ompared w ith s imilar m oulds f rom t he s econd f lagon. I t i s i maged b y t he r etracted s cintillator d etector ' C ' w hich g ives h igh r elief c ontrast t o t he g old-coated m ould. T his i s c ompared t o F ig. 2 2, s howing t he s ame s ample v iewed w ith t he s plit s olid-state d etector ' A ' a bove t he s ample a nd s witched t o t he t opography m ode. T he f ormer l atter. i n t he 2 2. A i n t he

g ives a f ar m ore ' real' i mage w ith m uch b etter d etail t han t he F or e xample, t he l ow p rofile t urning l ines o n t he s ample s tub u pper l eft h and c orner o f F ig. 2 1 a re t otally m issing i n F ig. s econdary e lectron i mage b y c omparison a lso s hows l ack o f d etail l ow-profile s cored l ines o n t he m ould.

3 9

F ig. 1 9. F urnace w all s howing v ery f ine d etail c ompositional c ontrast o f t he l ow-fired c eramic, a t l ow m agnification.

F ig.

2 0.

H igh-fired r egion o f t he f urnace w all s howing d iffusion z ones

i n t he g lassy m atrix a nd i ntrusions o f l ead-rich g lass.

4 0

F ig. 2 1. T opographic i mage o f a g old c oated s ilicone r ubber m ould t aken w ith t he r etracted s cintillator d etector, s howing h igh r elief c ontrast w ith g ood d etail.

F ig. 2 2. T opographic i mage o f t he s ilicone r ubber m ould t aken w ith t he s olid-state d etector a bove t he s ample. N ote t he l oss o f f ine d etail.

4 1

C harcoal o r w ood s ections c an s ometimes b e d ifficult t o e xamine i f s pecimen c harging o ccurs w ithin t he v essels. B SE i maging f rom d irectly a bove t he s ample i n t he c omposition m ode s uppresses c harging a nd e ffectively b lacks o ut t he v essel p ores, l eaving a c lear a nd d etailed s ection. T his g ives a ' drawing' q uality t o t he s ection a nd e mphasizes t he v essel s ize d istribution t hat f orms t he s equence o f s pring a nd s ummer g rowth a nd w inter

d ormancy .

F igure 2 3 s hows a f racture s ection

t hrough a p iece o f h earth c harcoal f rom a '4 C s ample. T he r oughness o f t he c arbon-coated f racture s ection i s b eneficially f lattened i n t his c omposition m ode i mage. T he n egative f orm o f t he i mage m ay b e p referred a nd i s s hown i n F ig. 2 4.

C onclusions A tomic n umber o r c omposition c ontrast i maging i s n ow a r outine p ractice f or e xamining p olished s ections o f a ll t ypes o f m aterial. I ndeed, i t i s o ften t he s ole t echnique u sed. T he b asic r ules r egarding t he g eometry o f t he d etector w ith r espect t o t he s ample, B SE y ield w ith r espect t o p robe c urrent, a nd t he e ffects o f t he a ccelerating v oltage o n t he r esulting i mage o f t he s ample a re s traightforward. B earing t hese r ules i n m ind, t he S EM may b e i n a l ess t han i deal c ondition f or B SE i maging w ith t he f ixed parameters d ictated b y E DX a nalysis. T herefore, f or b est r esults, B SE i maging n eeds t o b e d ecoupled f rom m icroanalysis, a lthough c ompromise c onditions c an b e s atisfactory, particularly w hen t he t ype o f m aterial u nder e xamination i s k nown. W ith u nknown s amples i t i s b est t o i nitially u se l arger probe c urrents ( than f or E DX a nalysis), a l ong w orking d istance a nd, w hen p ossible, f ast s can r ates f or g eneral c ontrasts m ore o bvious. T his a dvantage o ver B SE

i nformation s econdary

' slow-scan o nly'

t opographic

archaeology

s urvey w ork t o m ake t he c ompositional i s w here ' TV' r ate d etectors h ave a r eal

t han c an

b e

e lectron

t he

i maging

d etectors. i s

s econdary

p erhaps e lectron

o btained b y t his m eans. i maging/ t he

t raditional

l ess m ode,

g enerally b ut

u sed

m uch

F rom o ur v iewpoint s taple

d iet o f

i n

u seful i t

S EMs,

i s

t hat

i s n ow o ut o f f ashion. O ne o f t he r emarkable t hings a bout t he c ompositional c ontrast t echnique i s t hat i t i s s o c omplementary t o o ptical m icroscopy. A part f rom c arbon c oating f or t he S EM, s ample p reparation i s e ssentially t he s ame f or b oth t ypes o f e xamination. T he h igh q uality p olished s pecimens r equired f or l ight m icroscopy a re i deal f or c ompositional i maging i n t he S EM. U se o f t he c ompositional c ontrast t echnique h as r evolutionised o ur c apability f or s tudying a rchaeological m aterial.

Acknowledgements T he f ollowing R esearch L aboratory s taff a re t hanked f or t heir c ontributions t o t his p aper: D r. M .S. T ite f or u seful c omments, S usan L a N iece f or p roviding F igures 1 0 a nd 1 1, a nd T ony M ilton f or p rinting t he m icrographs. T he s cintillator d etector u sed i s m anufactured b y C ambridge T echnology, a nd t he s olid-state d etectors u sed a re J EOL p roduction-standard d evices.

4 2

e

. 4 . . .• .. . .zr i wr •3 • •iv • , . : % . 12 141. , h t e ete tiefe l , 14 ,y » . ; ; :• :. . : r . ; • i i •:• ' . . . '7 . •. "* : . ; '« ' . . ; «' ; "

r 3 : 4 , ;; . , s . ; . .4• . . , , rt vi . , : . .› , y e e t . A . A .,' i . e . .‚ ` 7 ‚ 1 b ,.* .

2 c.

% i t 'e ‘& , : y

I x

. 4 4 . z . . f r

•

;

o i t A x y ,1 . 1 . 10 , : 2 . ,. . . , .. i f r

41 34

t z :

fe Z‘i

e t24). : A ssi •

iv e l l t> ' e *. • * ;; . ft:;

.•

5 4 :

• • -• 4f1 -04 • •

t i rje . 1 4 3 , . b e

' .i . * , r; : . ' ;' . .i ' ; • : : , .

.i t ikr e fer ie

.

h

•e •

4N it tee

..

. .

K

› •• . .2 4 . *• : , . ‘ , . . . ..•, , .• .• •' . ! . . ,' ,i : . •t • zu . e. %. .e t " ; K . :. • s te i l ik z t . 4 . 4 1 tr ,e ; i : : 4 , •. • • • .: 99 : j * I . h . f te a l * ' . : 4 ( • • i f e • I t . e ; • e • : • d e : b e e . . . ; . :, 43 . :t ; s . ,„ , ef i . , . , A . ..4, -?rtf b i4 r ? ; :

*N

*A P ' .

4 44 7

,

0 4 el , g u t . .e g e • 4. 2. „ letv e , « . . ` p, i

‘ii i

r a . .te •I r k t . g e

. #f

e u f b

%

i

i > al t

t -

1 .3 . 1 .44 ,. i . *2

4.

4

e

. .

f

., ' . .• • . :o r' F .: s e .:,5 : . , ; • : i i . 4 , 4 : / : . ; • .4. : . 4 1 , . , ., • . ,4 " . , ,. . . . . . i • l › . . . % : . , • : • • • : . 1 . i . • : ;• . • :d r . „ i t e e * . r4I P .• d o b ' * • ' ` . " J . t . .42 t ne i * * > . . • .eZ vi l i e* * b .. * 1 4 ,4 1 , ,g , : t : e r .3g t e # , * 2 d ` e a 4 '. ‚ f' . •. c r i -e •/ n i b .7 0• 4

%, A ,

• ,

,,

S

I I*

4

• e. i

,•;.

. r . . . ,

, j;:e ;4 . :

e

4

l

:

I • i•

: .• . .

I N

"

.

d ibe

"A

I

1 71

4

•. L i o ,

• 4 #

• $ • * , : • :• k * 4 1 .4 4 ,

v ..12 b i

F ig. 2 3. F racture s ection o f a c harcoal s ample v iewed w ith t he s olids tate d etector i n t he c omposition m ode. N ote h ow t he u neven f racture s ection i s a pparently f lattened. T he a nnual g rowth r ings a re c learly s een a t l ow magnification, i n t he h orizontal d irection, w hile m edullary r ays a re t he v ertical w hite l ines o n t he m icrograph.

F ig.

2 4.

N egative i mage o f t he c harcoal s ample.

4 3

t he

References G oldstein,

J .I.

e t

a l.

M icroanalysis.

L ondon:

H all,

L loyd,

M .G.

a nd

1 981.

S canning

E lectron M icroscopy a nd X -Ray

P lenum P ress. G .E.

1 981.

T he

S EM

e xamination

o f

g eological

s amples w ith a s emiconductor backscattered e lectron d etector. M ineralogist 6 6: J EOL,

1 980.

s ystem . J oy,

B ackscattered e lectron

J EOL N ews

D .C.

S canning

1 973.

1 8e:

1 :

D .E.

t he

1 974. S EM

S ystems 1 8:

T he

c ontrast.

7 th Annual

a nd e lectron optics

c ontrol

C rystallographic e ffects f rom i mperfect c rystals.

o f P hysics C onference S eries

c hannelling

i mage

1 5-18.

E lectron M icroscopy:

N ewbury,

American

3 62-368.

I n

I n

T he I nstitute

2 88-293.

o rigin,

S canning

S ymposium,

a nd Applications.

pp.

d etection

a nd

u ses

E lectron M icroscopy, 1 048-1057.

o f

e lectron

P roceedings o f

I IT R esearch

I nstitute,

Analysis.

C ambridge:

C hicago. R eed,

S .J.B.

1 975.

E lectron

Microprobe

C ambridge U niversity P ress. S chur,

K .,

B laschke,

R .

a nd P fefferkorn,

G .

1 974.

I mproved c onditions

f or b ackscattered e lectron S EM micrographs o f polished s ections u sing a modified

s cintillator

P roceedings

o f

t he

R esearch I nstitute, W ells,

O .C.

1 974.

d etector.

7 th

Annual

I n S EM

S canning S ymposium,

E lectron pp.

M icroscopy,

1 004-1010.

I IT

C hicago. S canning

E lectron

M icroscopy.

N ew York:

M cGraw

H ill. White,

S .H.,

S haw,

H .F.

a nd

H uggett,

J .M.

1 984.

T he

u se

o f

backscattered e lectron i maging f or t he petrographic s tudy o f s andstones a nd s hales. J ournal o f S edimentary P etrology 5 4: 2 : 4 87-494.

P ART I :

ARCHAEOMETALLURGY

4 5

S EM A ND M ICROPROBE ANALYSIS: D avid A .

C OMPLEMENTARY METHODS OF I NVESTIGATION

S cott

I ntroduction S canning e lectron m icroscopy, e specially w ith e nergy d ispersive a nalysis f acilities, r epresents o ne o f t he m ost u seful t echniques f or t he v isual e xamination o f a ncient m etallic s pecimens. A t t he p resent t ime, s ome s canning e lectron m icroscopes a re a vailable w ith s ample c hambers s ufficiently l arge t o e nable c omplete o bjects s uch a s h and g uns o r f ragments o f v ery l arge o bjects t o b e a ccommodated. F or c arrying o ut c ompletely n on-destructive a nalysis o f t he u nprepared s urface o f m etallic a rtefacts, t his f acility i s e xtremely u seful. T he k ind o f s amples, o n t he o ther h and, w hich c an u sefully b e e xamined b y e lectron p robe m icroanalysis, o r e lectron m icroprobe a nalysis ( EPMA) a s i t i s o therwise k nown, a re m ore l imited i n s cope a nd s ize. T he i deal s ample f or E PMA s tudy i s a p olished s ection w hich c an b e c oated w ith a t hin f ilm o f c arbon. C arbon c oating i s u sually n ecessary i n E PMA a nalysis b ecause h igh a ccelerating v oltages a re u sed i n o rder t o o btain s ufficient x -ray e mission t o g ive g ood a nalytical d ata. T he a ccelerating v oltages m ay b e t ypically 2 0kv o r 3 0kv. T he f unction o f t he t wo m ethods o f a nalysis a re e ssentially d ifferent: t he S EM i s p rimarily d esigned a s a n i maging m achine w ith a nalytical f acilities o f s econdary i mportance w hilst w ith E PMA, a nalysis t akes p riority o ver i maging. W ith m odern E PMA m achines, s uch a s t he J EOL S uperprobe 7 33, t he q uality o f t he i mage o btained m ay, n onetheless, b e e xtremely g ood, a lthough t he d egree o f s pecimen m ovement i n t he c hamber i s u sually more r estricted t han t hat w hich t he S EM p ermits. O lder E PMA m achines o nly a llow t he p olished s ample t o b e m oved i n i ts p osition r elative t o t he e lectron b eam b ackwards a nd f orwards o r u p a nd d own w hilst r etaining t he s ame g eometrical p osition a s f ar a s t he b eam i s c oncerned. L imited s ample s ize a nd m ovement, c ombined w ith a n e mphasis o n a nalysis h as m eant t hat t he e lectron m icroprobe h as n ot r eceived p articularly w idespread a ttention. T his i s c ompounded b y t he p rice o f t he i nstrument w hich, a t 1 986 p rices, m ay c ost $ 400,000. E PMA h as f ound m ost f avour w ith g eologists a nd m etallurgists a nd i s l ess s uitable f or o rganic m aterials w hich m ay b e d amaged b y t he b eam, e ven i f c arbon c oated . A w ide r ange o f a ncient m aterials m ay h owever b e e xamined b y E PMA, s uch a s c eramics, s lag, m etallurgical w aste p roducts, r ock a nd m ineral s amples, c orrosion p roducts, c ore m aterials a s w ell a s m etallic a rtefacts t hemselves. a nalysis o ften s tart a s r eflected l ight o ptical c arefully i n i nterest c an

I nvestigations t o b e f ollowed u p b y E PMA t hin s ections, o r a s p olished s ections f or m icroscopy. H aving e xamined t he m aterial

r eflected l ight m icroscopy m ode, b e o btained b y E PMA . T here a re

a nalyses o f a reas o f u sually t he f ollowing

f acilities o n t he E PMA i nstrument: ( 1) ( 2) ( 3)

e nergy d ispersive a nalysis. c rystal s pectrometers f or w avelength a nalysis. l ine s canning a cross t he s pecimen s urface u sing e ither w avelength o r e nergy d ispersive m odes.

4 7

e lemental m apping o f s elected a reas o f t he s pecimen u sing e ither w avelength o r e nergy d ispersive m odes. a nalysis p rogrammes w hich p rovide p rint-outs i n t erms o f o xides b ased o n f ixed r atios b etween t he e lements s ought a nd o xygen. s torage o f e lemental s tandard d ata w ith r eference t o c obalt. b ack-scattered a nd s econdary e lectron i maging: i n m ore r ecent m achines t his m ay b e q uite s atisfactory f or o btaining g ood i mages, E lements d ifficult t o

a lthough t he S EM i s g enerally s uperior.

b elow a nalyse

s odium i n t he p eriodic t able a re g enerally b y E PMA, b ut u sing c rystal s pectrometers e ven

o xygen m ay n ow b e a nalysed w ith s ome c onfidence. I t i s s tandard f or m any m etallic e lements t o b e p rofiled a nd t he i nformation s tored f or f uture a nalyses b y r eference t o a c obalt s tandard w hich i s c arbon c oated a t t he s ame t ime a s t he s pecimens f or s tudy a re c oated . W ithout c oating, e ven v ery c onductive s amples m ay b uild u p a s urface c harge, e specially w hen t hey a re m ounted a nd p olished i n a r esin m ount, a s m ost a rchaeological s amples a re. A d ab o r s treak o f s ilver p aint t ouching b oth t he s pecimen h older a nd s pecimen m ay a lso b e n ecessary, a lthough s ome c are m ust b e t aken t hat t his d oes n ot m ask o ff a reas o f i nterest i n t he s ample. T he E PMA i s e quipped w ith g ood o ptical m icroscopes w hich a llows v isual c ontact w ith t he c oated s ample. 'T his i s m ost n ecessary, p articularly w here s elected a reas o f

i nclusions,

c orrosion p roducts,

o r s urface f eatures a re t o b e

e xamined. C arbon c oating a ffects t he v isual c ontrast b etween a reas o f t he s pecimen w hich m ay b e o f d ifferent c omposition, s o i t i s t herefore i mportant t hat t he c arbon c oating i s n ot e xcessively t hick . I t i s a lso i mportant t hat t he a rea s elected b y o ptical e xamination i s c entred e xactly f or t he p osition o f t he e lectron b eam, o therwise w hen t he s ample i s p resented t o t he b eam t he a rea a nalysed i s n ot t he s ame a s t hat s elected o ptically. S pot a nalyses may n ow b e c omputer d riven, a s m ay b e t he w avelength s pectrometers w hich w ere f ormerly r ather t imec onsuming t o u se. N either t he S EM o r E PMA p rovide t he p erfect s olution t o t he p roblems o f i nclusion c haracterisation i n a rchaeological m aterial. I f t he i nclusion o r f eature i s o nly s ome 2 -3 m icrons a cross t hen i t i s v ery d ifficult t o e xclude m atrix e xcitation a s w ell. A n e xample o f t his p roblem i s s een w hen a ttempting t o i dentify t he p recipitation o f A gAu r ich p hases i n g old-copper-silver a lloys w hich a re j ust b eginning t o s how s igns o f t wo p hase c omposition. T he s hape a nd s ize o f t hin p lates o r p articles, e specially w hen t hey d iffer o nly s lightly f rom t he m atrix c omposition m ake t hem v ery d ifficult t o a nalyse. L arger i nclusions, m easuring p erhaps 1 0 m icrons a cross p resent l ess t rouble. A s a n e xample, l et u s l ook a t t he n ature o f t he m ineral i nclusions i n a p lacer

g old

t ributary C olombia.

8 5.1%

o f

A nalysis C u: n d

n ugget t he

f rom R io

t he

a rea

M agdalena

o f o n

t he t he

R io

d e

l a

M iel,

a w estern

C aldas-Antioquia

b order,

o f t he g old m atrix b y E PMA g ave t he f ollowing d ata: A u: A g: 1 1.7 F e: n d P t: n d T otal: 9 6.8%. W ith t he E PMA,

s pot a nd l ine s cans f or g old a nd s ilver c an b e c arried o ut t o s ee i f a ny e lemental v ariation o ccurs w ithin t he g old m atrix; h ere t he p lacer

4 8

n ugget w ithin

w as

f airly

t he

g old

u niform

w ere

s amarium,

g adolinium

m onazite,

a nd

f ound a nd

a s pecial

E PMA c ould b e

u sed

t o

i n

c omposition.

p hosphorus. a nalysis

o btain

T he

E PMA

b ecause

i s

t he

q uantitative

u seful

c asting

material

c arbonised p lant e xample

l ess

w ith

o f

m aterial o f

m ineral

f or

may

w hich t his

i nclusions

c erium,

i nclusions o perating

n eodymium,

a re a t

i nformation.

t herefore

3 0kv T he

o n

t he

p rint-out

1 . t he

r emains,

i tself

material

T he

p rogramme

f rom t his a nalysis i s g iven i n T able

a ssociated

T he

t o b e r ich i n l anthanum,

s tudy

o f

i nclusions

a s

c ore

m aterial.

T his

i s

c omponents,

s uch

a s

s uch c ontain

i s

n ot

k ind

o rganic

w ell

i s

s uited

g iven

i n

w hich

t o E PMA

F igure

a re

s tudy.

A n

T he

S EM

1 .

s econdary e lectron i mages a re f rom a f ragment o f c ore m aterial c omposed o f b y

c lay a nd c harcoal. T he o bject i tself was a d ebased g old a lloy c ast t he l ost-wax p rocess: a T airona n ecklace p iece f rom t he S ierra

N evada

d e

S anta

i nteresting s een

a

M arta

d etail

f ragment o f

w ithout

r eference

p ercentage

t he

p its,

m aterial

o f

C olombia.

c omposition; c ell

o f

a nalysis,

c arbon present

i n

S EM

e mployed

t he material,

r ecognisable

h ardwoods,

c annot b e

t aken

h ere

r eveals

l a a nd b c an b e

c ontaining

t ropical

i dentification

T he

i n F igures

s tructure

t ypical

Microchemical o f

North

c ore

a woody

v estured

p resent.

i n

t he

o f

r emains a t

o f

t o

a lthough

a ny

f urther

d etermine

g ave a r esult o f

t he

1 9.66%,

f airly t ypical f or s ome o f t hese l ost-wax c asting c ores. T he c an

b e

s tudy

e xamination e lemental p ipe

o f

c arried

f rom

c orrosion

o ut

may

b e

m apping t he

i n v ery

o f

b e

g rains

t he

material

t he

d epressed c orrosion

has

b een

s een

a reas t he

s lightly

distribution ( composition

i n

the

e xample

m etallic

E PMA :

o f

t he

o f

D epartment

2 .

C orrosion

b oth E PMA

f ragments

m ethods r esults

o f f or

a d ebased g old pano f

h as

N arino, l eft

S outhern

s ome

o f

t he

i mage

s hown

i n

F igure

2 a.

A s a r esult

t owards t he s urface r egion o f t his p iece n ote

a lso

t he

i n

t his

g old-copper-silver

silver

2 5.9%

t he

i n a s ea o f c orrosion c orresponding t o

e nhanced;

of

a bout

B SE

c ontent

c orroded

c ross-section

F igure

t he

a nd

P upiales,

i solated

i n

g old

o f

a nd

S EM An

a polished

c an

o f

t he

u seful.

Municipio

C olombia, o f

p roducts

both

g old;

6 2.4%

c opper

s lightly

a nd

4 .0%

s egregated

s ilver

a lloy

b y

E PMA

a nalysis). A f urther e xample o f t he u se o f t he E PMA f or t he s tudy o f c orroded m etallic m aterials i s g iven i n F igures 3 a nd 4 . F igure 3 s hows a s ketch o f a c ross-section o f a b ronze r od f rom I ran ( Scott, 1 985). a cross t his

F igure t he

k ind,

4 s hows

c orroded

t he

r od.

s lowly ' h aving

c opper T he

t he

a nd

t in

i nformation

d istributions r evealed

b y

a s l ine

t hey vary s cans

s pecimen a cross t he p ath o f t he b eam,

o f c an

b e e xtremely u seful i n a ttempting t o i nvestigate s urface c omposition o f g ilded

o r

s ilvered

c orrosion e ffects.

o r

t inned

s urfaces,

o r

f or

i nvestigation

o f

I n F igure 4 c an b e s een a n umber o f d ifferent z ones

o f s tructure o f t he r od w hich c an b e d escribed b riefly a s f ollows: Z one

1 :

bronze m etal

g rains c ontaining a bout 9 .5% t in g rading

i nto a r egion o f c orroded metallic g rain r emnants. Z one 2 : Z one

3 :

a r egion o f massive t in p recipitation. c ompact

c uprite

l ayers

i nterspersed w ith s ome t in

precipitation. Z one 4 : Z one

5 :

t he o riginal s urface o f t he r od. t he

o uter

c orrosion c rust w hich o nly c ontains v ery s mall

t races o f t in.

4 9

Table 1 .

Monazite I nclusions

A t ypical

EPMA print-out

Cambridge

Mark

U niversity a pparent A fter

ZAF

5

f or

t he

c orrections

t he

a nalyses

c arried

a re have

T he s hown

been

f it

i n

f igures out

of a re by

t he

t he f or

t he

f irst

part

o f

applied,

quoted EPMA

t o

are

a nd

a n

oxygen

concerned

t hree

r eally

c arried

Dept.

i ndex

t he

e lement

f rom Colombia

a nalysis

a t

t hen t he quantitative print-out

percentage

Although

a quantitative

Microanalyser

London.

c oncentration

monazite a ssigned,

f or

X -Ray

C ollege,

i n P lacer Gold N ugget

d ecimal only

of

out

data the

and

content

f or

places,

a ccurate

to

t o t he

t he

results one

CONC.

ERROR

LA

7 .820

C E

2 2.300

0 .256

P R

2 .655

0 .256

( WT.

% )

0 .190

ND

1 4.486

0 .199

S M

2 .169

0 .157

EU

0 .384

0 .176

GD

0 .796

0 .138

DY

0 .047

0 .114

P

1 2.951

0 .056

CA

0 .083

0 .024

FE

0 .046

0 .054

2 S IGMA

MN

0 .032

0 .089

2 S IGMA

T I

0 .013

0 .045

2 S IGMA

2 S IGMA

NUMBER OF OXYGEN ATOMS - 1 ( 1 2 3 ZAF) 3 0.00 KV

T ILT=0.00

S PECTRUM:

1 037.A4

ELEVATION=75.00

AZIMUTH=0.00

COSINE-0.00

LAST ELEMENT BY S TOICHIOMETRY ELMT

Z AF

% ELMT

%OXIDE

FORMULA

LA

0 .901

C E

0 .945

8 .691

1 0.193

0 .039

2 3.710

2 7.771

0 .107 0 .013

P R

0 .946

2 .807

3 .285

ND

0 .942

1 5.419

1 7.984

0 .067

S M

0 .924

2 .347

2 .722

0 .010

E U

0 .903

0 .426

0 .493

0 .002

GD

0 .774

1 .029

1 .187

0 .004

DY

0 .865

0 .055

0 .063

0 .000

P

1 .041

1 2.477

2 8.593

0 .254

CA

1 .129

0 .074

0 .103

0 .001

FE

0 .942

0 .049

0 .062

0 .001

MN

0 .942

0 .000

0 .000

0 .000

T I

1 .002

0 .000

0 .000

0 .000

O

0 .303

2 5.372

0 .000

1 .000

9 2.456

9 2.456

TOTAL

5 0

f or

decimal

F IT I NDEX = 2 .86 APP.

both

oxide.

place.

ELMT

t he

print-out.

i s g iven below, and

on a

Geology,

F ig. 1 . S EM s econdary e lectron i mages o f a f ragment o f c asting c ore f rom a T airona n ecklace b ead. a . L ow m agnification v iew s howing e xtensive r emains o f c arbonised p lant m aterial u sed i n t he f abrication o f t he c ore b efore t he w ax w as a pplied f or m odelling o f t he s hape. S cale = 3 0 m icrons.

b .

H igh m agnification v iew o f t he p its e vident i n

t he l arge w ood s tructure o f F igure l a. T he p its i n t he w ood h ere c an b e s een t o b e v estured, t ypical o f t ropical h ardwoods. S tudies s uch a s t his c an p rovide i mportant c lues t o m anufacturing t echnique a nd l ocal p references m icrons.

i n

t he

f abrication o f

l ost

5 1

w ax c asting

c ores.

S cale - 3 0

F ig.

2 .

E lemental

m aps

d ebased g old p an-pipe e lectron v iew s howing o ccurring a s i solated s howing

s ome

f or

g old,

c opper

a nd

s ilver

a cross p art o f

a

f rom N ar Ao, C olombia. a . B ack-scattered s urface t opography w ith s ound m etal g rains e levated a reas. b . E lemental m ap f or g old

e nrichment

t owards

t he

o uter

s urface

a s

a r esult

o f

c orrosion. N ote t he u ncorroded m etal g rains a ppear l ess r ich i n g old, b ecause h ere c opper h as n ot b een l ost. c . E lemental m ap f or c opper, s howing t hin l ayer o f c opper r ich c orrosion t o t he o uter s urface a nd s everal w ell-preserved m etal g rains i n t he c orroded m aterial w hich c orrespond t o t he e levated r egions s hown i n F igure 3 . 2 d. E lemental m ap f or s ilver s howing s ome s egregation i n t he c orroded m atrix. T he m atrix i tself i s n ow m ostly c uprite c ontaining b oth g old a nd s ilver. T he s ilver i s c orroded h ere t o s ilver c hloride.

5 2

F ig. 3 . S ketch o f t he c ross-section o f o bject A l 8 62, t he b ronze r od f ragment f rom I ran, s howing t he l ocation o f t he e lectron m icroprobe l ine s can f or c opper a nd t in: a . b ronze m etal g rains c ontaining 9 .5% t in, b . c ompact l ayers w hich a re p rincipally c uprite a nd t in o xide i n s egregated a reas, h igh C a c ontent

c .

o riginal s urface o f t he o bject,

( soil m ineral i nclusions),

e .

d .

s ome r egions o f

o nly t race a mounts o f t in

i n t he o uter c orrosion c rust, f . o uter a reas c ontain F e a nd C u i mmediately a djacent t o t he s urface.

s ome

S n,

C l,

C a,

COPPER T IN

ZONE 5

Z ONE 4

ZONE 3

Z ONE 2

ZONE 1

F ig. 4 . S ketch s howing t he p rincipal z ones t o b e f ound i n t he c rosss ection o f o bject A l 8 62. T he n ature o f t he d ifferent r egions i s e xplained i n t he t ext. - c opper, -- - - - t in.

5 3

T he o ther e lements m entioned i n F igure 3 w ere a lso d etermined by E PMA a nalysis u sing i ndividual s pot d eterminations i n d ifferent r egions. D espite f or

d ifficulties

w ith

c haracterisation

o f

s pot

t he

a nalyses,

c omposition

t hese o f

a re o ften v ery u seful

t he o riginal m etal b efore

c orrosion, s imply by a nalysis o f u ncorroded metallic g rains, a nd i t i s a lso t he m ost c ommonly u sed t echnique f or t he s tudy o f r ocks a nd m inerals products.

i n

T hese

t hin

b rief

s ection,

e xamples

a s

s how

w ell

s ome

a s

o f

a rchaeometallurgical

t he

l imitations

waste

a nd a dvantages

o f E PMA a nalysis: f or f urther d etails c oncerning t he t echnique t he r eader i s r eferred t o t he v ery r eadable a ccount provided by L ong ( 1977) a lthough

i t

s hould b e

b orne

i n mind

t hat

t he

s cope

a nd s ophistication

o f t he probes c urrently a vailable a re f ar i n a dvance o f t hat d escribed.

References C ope, f or

L .H.

a nd Warren,

d etermining

C hemical 2 49.

a nd

R .

H allerman,

Metallurgical

G .

a nd

o f

L ong,

J .V.P.

1 977.

L ondon:

A cademic P ress. D .

P roceedings 4 11-429.

T ite,

M .S.

M ethods

1 973. o f

t he

1 972.

S cott,

D .A .

1 985.

1 969. t he

a nd G .

N ew York:

i n

I n M ethods o f

C oinage,

probe

Metallurgical

T he

precision Marton

8 ,

pp.

i nfluence o f

( eds.),

2 37-

L ondon. of

t he

e lectron

probe

E lectron

P robe

A cademic P ress. m icroanalysis.

D eterminative

8 th National

N ew Orleans:

L ondon a nd N ew Y ork:

on

E lectron

P hysical

O 'Boyle,

M .L.

T onsimis

1 97-225.

( ed.),

c oins.

S pecial P ublication No.

s pecimens

I n A .J.

M icroanalysis, pp.

a ncient

I nvestigation o f Ancient

P icklesimer,

metal

m icroanalysis.

C omparison o f EPMA w ith o ther methods

c omposition o f

Royal Numismatic S ociety:

preparation

pp.

1 972.

t he bulk

I n

Mineralogy,

a pplications

o f

J .

2 nd

Z ussman e dition.

t he m icroprobe.

I n

Conference o n E lectron P robe Analysis,

E lectron P robe Analysis S ociety o f America.

M ethods

o f

P hysical

Examination

i n

Archaeology.

S eminar P ress. P eriodic c orrosion phenomena i n b ronze a ntiquities.

S tudies i n C onservation 3 0:

4 9-57.

5 4

M ETALWORKING T OOLS A ND W ORKSHOP P RACTICES: METAL S URFACES VIA S ILICONE R UBBER MOULDS

I NTERPRETATION

O F WORKED

Dana E . G oodburn-Brown

I ntroduction

w hich

T his i s

p aper f ocuses o n t he r ecovery o f t echnological i nformation s tored o n t he s urfaces o f m etal a rtefacts. I t i s a n on-

d estructive t echnique o f a nalysis, w hereby a s ilicone r ubber m ould ( Dow C orning S ilastic 9 161) i s t aken f rom t he s urface o f a n a rtefact t o b e s tudied. I t i s t his m ould, r ather t han t he a rtefact i tself, w hich i s then s ectioned and manipulated u nder t he m icroscope. T he m agnifications u tilized s pan a r ange f rom x 20 - x 1000 a nd a re d ependent o n t he l evel o f q uestion b eing a sked a bout t he s urface t exture. T he m etalworking t ools, t ype o f m aterials b eing u sed i n t he w orkshop, a nd e ven w rought a nd a nnealing p rocesses u sed i n t he p roduction o f a n a rtefact m ay b e e xamined. T he t erm ' workshop ' h ere r elates t o t he hypothetical surroundings o f a m etalworker d uring f abrication p rocesses, a nd s pecifically r efers t o t he e ntire c ollection o f t ools a nd m aterials i nvolved i n t he p rocess o f manufacture.

T oolmarks T he f irst l evel o f i nterpretation i s c oncerned w ith t ool m arks; t hat i s, t he i dentification o f t ool t ype a nd u ltimately t he r ecognition o f i ndividual m arks o r " signatures". T ool t ypes may b e d istinguished b y t he m anner i n w hich t hey a re u sed i n m anufacture; f or e xample, a S CRIBER i s

o ften u sed a s a p encil,

i ts

s harp p oint b reaks t hrough t he

m etal s urface a nd l eaves a c haracteristic b urr. A T RACER i s u sed w ith a h ammer a nd d epresses m etal; w hereas a G RAVER i s h and-held a nd a ctually c uts a way m etal f rom i ts path. A P UNCH a lso d epresses m etalb ut i t i s a pplied w ith a s ingle b low, w hereas a t racer i s h ammered a long i n s uccession i n o rder t o c reate l inear d ecoration. B y e xamining t he c haracteristics o f a t oolmark, t he t ype o f t ool u sed t o c reate t he m ark m ay b e d etermined. T his k ind o f s tudy i s b est c arried o ut i ndirectly, v ia s ilicone r ubber m oulds o f a rtefacts' w orked s urfaces. A side f rom t he r ecording o f f ine d etail, t he u se o f a s ilicone r ubber m ould i n t his w ork h as t wo major a dvantages. F irstly, i t f acilitates a n e xtensive t echnological e xamination o f a n a rtefact, t aking p lace q uite r emoved f rom t he a rtefact i tself; a nd s econdly, i t r eproduces a r aised i mage o f t he t oolmark, r ather t han t he r ecessed f eature w hich i s o bserved w hen e xamining a n a rtefact f irst-hand. T he v alue o f t echnological r esearch c arried o ut o n s ilicone r ubber m oulds i s a ttested t o b y t he w orks o f L arsen ( 1985), S horer ( 1984), L owery, S avage a nd W ilkins ( 1971). S tated s uccinctly: " indirect e xamination, s ince i t p resents t he b ottom a nd s ides o f t he g roove r elief u ncamouflaged b y c olour d ifferences i n s tain o r p atina,

i n i s

a lmost a lways m ore i nformative, a nd w e w ould h esitate t o a ttribute m any t ypes o f l ine w ithout i t" ( Lowery e t a l., 1 971:176).

5 5

T ool t ypes may u sually b e d istinguished w ith t he u se o f a h and l ens ( x10) o r a n o ptical m icroscope; a lthough t he g reater r esolution a nd d epth o f f ield a vailable w ith t he S EM m ay b e r equired i n s ome c ircumstances. I t i s i n t he s earch f or i dentifying c haracteristics o f i ndividual t ools t hat t he S EM i s o f g reat v alue. S cars o r n icks o n t he f ace o f a t ool w ould l eave d etails w hich m ay b e i dentified v ia s ilicone r ubber m oulds. B enner L arsen ( 1984) s peaks o f t oolmarks a s b eing " fingerprints" o r t he " signatures" o f t he i ndividual t ools u sed. I n h is s tudy o f S candinavian I ron A ge m etalwork, u sing t he S EM a nd s ilicone r ubber m oulds, h e h as b een a ble t o v erify t hat t he s ame t ool w as u sed t o d ecorate d ifferent p ieces o f j ewelry r ecovered f rom a s ingle g rave a nd h as a lso o bserved t he u se o f a n i ndividual t ool o n o bjects r ecovered f rom m ore t han o ne g rave. I n a p reliminary s tudy w hich e xplores s ome a spects o f l ate P reC olumbian m etalworking t echniques, a n u nusual t racer t ype h as b een o bserved o n a d ecorated g old a lloy d isk f rom S outhern P eru ( Brown, 1 984). T he t ool a ppears t o h ave a b roken o r j agged e dge, a nd i t i s t his k ind o f c haracteristic d etail w hich m ay b e u sed t o v erify t he m ultiple u se o f a s ingle t ool ( Fig. 1 ). W hile t he r ecognition o f t ool t ypes i s r elatively e asy, t he i dentification o f a n i ndividual t ool's s ignature i s c omplicated b y v ariables i n t he manufacturing p rocess. F actors s uch a s t he a ngle o f a pplication, f orce o f h ammer b lows, a nd t he s harpening a nd/or w earing d own o f a t ool m ay h inder c omparative s tudies. T he b uild-up o f s urface d eposits o n a w orked p iece may a lso o bscure t he r equired l evel o f d etail f or t ool s ignature r ecognition. I t s hould b e n oted t hat m etal a rtefacts s hould b e c arefully e xamined i n o rder t o a scertain t he r esearch v alue, a s w ell a s t he c ondition, o f t he v arious s urfaces, p rior t o t aking a ny s ilicone r ubber m oulds.

S urface T exture:

( Imprints)

A nother l evel o f t echnological i nterpretation c oncerns i tself w ith t he i dentification o f s urface i mprints w hich r eflect t he f abric o f o ther m aterials u sed i n t he w orkshop. I n t he p reliminary s tudy d escribed a bove ( Brown, 1 984), a n a ttempt w as made t o d etermine t he t ype o f s urface ( e.g., a rtefacts w ere w orked.

l eather,

w ood,

s tone,

o r m etal) u pon w hich s uch

A s eries o f P eruvian g old a lloy p lume h olders a nd b eakers d epicting f aces w ith l arge p rotruding n oses, w as e xamined. I t h as b een s uggested t hat s uch i tems w ere manufactured o n w ooden f ormers ( Easby, 1 966). S ilicone r ubber m oulds w ere t aken f rom t he i nterior s urface o f t he a rtefacts a nd e xamined w ith t he S EM . T races o f w ood g rain s tructure w ere f ound t o b e p resent. A s

t he

p roduction p lume

S EM a nalysis o f

h older

t he w as

s uggests

a rtefacts, p roduced.

t hat a w ooden f ormer w as u sed i n t he

a f ormer w as

c arved a nd a n e xperimental

E xperimental w ork

s erves b oth t o

s upport

a nd a ugment o bservations o btained f rom t he o bjects t hemselves. T he s urface t exture o f t he s ilicone r ubber m ould t aken f rom t he i nterior o f t he e xperimental p lume h older s hows a c haracteristic r esemblance t o

5 6

1 5KH

F ig.

1 .

d isk,

S ilicone

2 726

r ubber mould,

1 00

t aken

O U

C RYST

f rom a P re-Columbian g old a lloy

i llustrating t oolmarks f rom a j agged e dged t racing t ool.

( Brown,

1 984).

F ig.

2 .

P air o f

P re-Columbian g old

a lloy vases

w hich h ave b een manufactured u sing a wooden f ormer

5 7

( private ( Brown,

c ollection), 1 984).

t hat o f t he t extures o n t he m oulds t aken f rom c orresponding f eatures o f t he p lume h olders a nd b eakers s tudied . E xamination u nder m agnifications g reater t han x 50 p rovides t he o nly r eliable m eans o f s urface t exture a nalysis; a lthough e ven h ere, o ne m ust b e a ware t hat t he s urface u nder o bservation r eflects t he e ntire m anufacturing p rocess, a s w ell a s c orrosion a nd p erhaps c leaning/restoration p rocesses s ubsequent t o f abrication. F or e xample, t he m etal s heet w hich w as u sed i n t his e xperimental w ork w as ' thinned' t hrough s teel r ollers b efore t he f orming p rocess w as b egun. W hen e xamining t he r esulting o verall t exture, c are h ad t o b e t aken n ot t o c onfuse t he s triations o f w ood g rain ( Fig. 3 ). w ith t he c haracteristic s triations r esulting f rom m odern ' rolled ' s heets ( Fig. 4 ).

M icrostructure T he t hird l evel o f i nterpretation d eals w ith t he m etal s tructure b y o bserving t he s urface w hich r eflects t he m etalworker's m anipulation o f t he m aterial's p hysical p roperties t hrough w rought a nd a nnealing p rocesses. D uring S EM a nalysis c arried o ut o n s ilicone r ubber m oulds o f s ome P eruvian g old a lloy a rtefacts, i t w as n oted t hat t he s ilicone r ubber w as c apable o f r eproducing t he c rystalline s tructure o f a n a rtefact's s urface. P referential c orrosion a t t he g rain b oundaries h ad o ccurred; c onsequently, t he s ilicone r ubber p icked u p t his m icrocrystalline c hange i n ' texture' ( Fig. 5 ). I n r esponse t o t his o bservation, a n a nalysis o f t he e tched s urface o f a n e xperimental a xe w as u ndertaken, i n c ollaboration w ith P eter S horer, a c onservation t echnologist w orking i n L ondon. S horer p rovided a s ilicone r ubber m ould t aken f rom t he s urface o f a c ast 5 t in-bronze a xe, w hich h e h ad h ammered a nd a nnealed 5 t imes ( working f rom t he c utting e dge t owards t he h afting h ole). S amples w ere c ut f rom t he s ilicone r ubber m ould f rom f our a reas, e ach o ne d epicting v ariously w orked a reas o f. t he b ronze s urface. S ample 1 r epresents d endritic s tructures " as c ast"; s amples 2 a nd 3 r epresent t he s urface a t i ntermediate s tages o f w orking; a nd s ample 4 r epresents t he s urface a t i ts f inal w ork-hardened s tate. E ach s ample ( approx. 1 c m s q.) w as c arbon-coated a nd e xamined w ith t he S EM a t v arious m agnifications: x 100, x 150, x 500, x 1000. T he x 1000 s eries i s i llustrated h ere ( Figs. 6 -9). T he c onclusions d rawn f rom t his p reliminary e xamination r ely o n t he a ssumption t hat c hanges i n t he m icrostructure f rom t he " as c ast" s tate t hrough t he i ntermediate a nd f inal w orking s tages m ay b e d etectable a t t he s urface o f a n a rtefact, u sing s ilicone r ubber a nd t he S EM. F urther w ork, w ith a l arger s ample o f m aterial, m ay e stablish m anufacturing p rocesses.

t he

a ccuracy

o f

i nterpretations

o f

s uch

I n o rder t o b etter u nderstand t he c hanges o bserved i n t he m icrostructure a t t he s urface, a nd t o e nable t he p ossible c orrelation o f s uch c hanges w ith v arious s tages i n t he w orking o f m etal, a m ore c ontrolled e xamination i s r equired. A p roposed s tudy w ould i nvolve t he c asting a nd w orking o f a b ronze b ar; s ilicone r ubber m oulds w ould b e

5 8

Fig.

3 .

Wood

f rom i nterior F ig. 2 ( Brown,

Fig.

4 .

g rain

S ilicone

experimental

s tructure

s urface 1 984).

w ork.

c ase), r eflect ( Brown, 1 984).

t he

o f

e vident

projecting

r ubber

mould

P arallel a ction o f

o n

n ose

t aken

s triations,

t hinning

5 9

t he

s ilicone o f

r ubber m ould

P re-Columbian

f rom

c opper

( raised s heet

s heet

f eatures

t hrough

t aken

vase,

s teel

s ee

u sed i n

i n

t his

r ollers

Fig.

5 .

G rain b oundaries v isible o n a s ilicone r ubber mould t aken f rom

t he s urface o f a P re-Columbian g old a lloy d isk

6 0

( Brown,

1 984).

Fig.

6 .

M icrostructure

o f

a n e xperimental bronze a xe,

a s ilicone r ubber mould s howing a portion o f t he a xe

F ig.

7 .

M icrostructure

e videnced o n h ammering.

a s ilicone

o f

t he

s ame

r ubber m ould

6 1

e xperimental

s howing

a n

a s e videnced o n

' as c ast'.

b ronze

i ntermediate

a xe,

a s

s tage

o f

F ig. 8 . M icrostructure o f t he s ame e xperimental m ould s howing a l ater s tage o f h ammering.

b ronze

F ig. 9 M icrostructure o f t he s ame e xperimental b ronze a xe, f inal w ork-hardened, c utting e dge.

6 2

a xe,

r ubber

s howing i ts

t aken

b oth

f rom

t he

e tched

s urface

s tage o f

working

( i.e.

I n

manner,

a r eference

t his

b ronze b e

a lloy

c ompared

s ections.

' as

c ast,

a s

w ith

t he

C ase

c ast', s et

c hanges

a bove,

may

b e

a nd

i n

s ection,

h ammered,

c ompiled

a t

a nnealed,

f or

t he

e ach

e tc.).

particular

i n t he m icrostructure a t t he s urface may

c hanges

s tudies

a s

a nnealed,

w ould

o bserved t hen b e

a t

t he

c orresponding

u ndertaken

i n

o rder

c ross-

t o t est t he

a pplications o f s uch e xamination o n a rchaeological m etals.

Conclusions T he s urface l evel c larification o f various t ypes

c an

b etter

b e

a nalysis d escribed h ere m ay a id i n t he p hases o f t he manufacturing p rocess. T ool

i dentified w ith

u nderstanding

o f

g reater

a ncient

a ccuracy

a nd

m etalworking

t his

may

r ecognition o f t ool k its f rom t he a rchaeological r ecord. i ndividual

t ool

r ecognition

o f matching

a n

o n

u nderstanding

o ne

o f

a brasion

f orming

d ecorative

s urface

preliminary

t echnique c ompared

l ies

i n

w ith

t oolmark

a nd o f

e mployed

b e

t o

i n

have a nd

n on-destructive a nalysis,

a

t he

T he u se o f a n

d etermined

c utting m etal

b een

i n

by

d escribed

T he

t he

s tages

o f

i s

t he

w ire

t o

t he

a bove.

s ignificance

n ature w hich

s heet,

a ddition

a nnealing

d ate.

t o

a nd

I t i s possible t o gain

t echniques,

hammering

c ross-section

may

" signatures".

w hich

t esting t he

o bjects

f inishing

s tages

i nterpretation

r eceived

more

t he m ethods

production, a nd

o r

l ead

t echnology

T he

has

o nly

o f

t his

process;

presently

a s

u sed

t o

r etrieve t his t ype o f d ata.

Acknowledgements I would

l ike

t o g ive

a nd i nspired m y w ork: P eter

S horer.

S andra a re

i n

T hanks

O lsen, a ny

f or

way

s pecial t hanks t o t hose w ho have both h elped

B enner Larsen, a lso

r eading

t o:

P hillip L owery,

Damian

G oodburn,

my manuscript.

r esponsible

f or

a ny

R ichard S avage a nd P eter

H owever,

e rrors

n one

w hich may

K vietok o f

s till

t he

a nd

a bove

r emain

i n

t his t ext. References B rown, D . T echniques. o f L ondon, E asby,

1 984. A R econnaissance o f S ome P eruvian G oldworking D issertation f or t he D iploma i n C onservation, U niversity I nstitute o f A rchaeology

D .

1 966.

American 2 4:

4 :

L arsen,

1 985.

B .

E arly

( unpublished).

metallurgy

i n

t he

N ew

W orld.

S cientific

7 3-81. V aerktoejsspor

O g

O verfladestruktur.

M etoder

T il

I dentification A f Vaerktoejsspor O g O verfladestrukturer P a A rkaeologisk Materiale. C openhagen, L arsen, t races.

S chool

o f

C onservation,

R oyal

D anish

Art

A cademy.

2 08 p p.

B .

1 985. I n

T he

T he T hird

G undestrup N ordic

C auldron,

C onference

S cientific M ethods i n A rchaeology 5 :

6 3

5 61-574,

i dentification o n

t he

H elsinki,

o f

Applications F inland.

t ool o f

L arsen, a nd

B .

1 984.

d ocumentation

T racing o f

t he

t ools

t oolmarks,

b y

o bjects f rom t he E arly G ermanic I ron A ge. L owery, s corper,

P .R.,

S avage,

t racer:

R .D.A .

t heir

i llustrated

a nd W ilkins,

n otes o n e xperiments

t races.

I dentification

t hrough

p unch-decorated

K UML 1 982-83: R .L .

1 971.

8 4.22:

6 4

g raver,

1 67-182.

S horer, P .H.T. 1 984. I nterpretation t hrough r usted 1 0th c entury V iking i ron s liding k ey. C openhagen 2 :

S criber,

i n b ronzeworking t echnique.

P roceedings o f t he P rehistoric S ociety 3 7:

T riennial M eeting,

1 69-180.

3 3-43.

r econstruction o f a I COM P reprints, 7 th

I CCROM,

R ome.

T HE

I DENTIFICATION

O F

O RGANIC

MATERIALS

P RESERVED

BY

M ETAL C ORROSION

P RODUCTS J acqui Watson

I n B ritain, o rganic o bjects a re w aterlogged e xcavations s olely a s t races

o ften i n t he

p reserved f rom n onc orrosion p roducts o f

a djacent m etalwork. C orroding i ron, c opper a nd l ead p roduce s alts t hat p rotect o rganic m aterials f rom m icro-organism a ctivity a nd p reserve r ecognisable m icrostructures. S uch c haracteristic s tructures c an f requently b e i dentified b y v isual e xamination i f w ell-preserved, b ut t he u se o f o ptical m icroscopy a lone i n s ome i nstances m ay p roduce i ncorrect i dentifications, a s m inerals a nd a lteration b y f ungi s uggest d iagnostic f eatures w hich w ere n ot a ctually p resent o n t he o riginal o rganic m aterial. I n s uch c ases, t he s canning e lectron m icroscope c an o ften b e e mployed t o c onfirm t he i dentification o f a n o rganic m aterial. The p otential o f t hese m ineral-preserved t races w as f irst r ecognised b y L . B iek ( 1963). S ince t hen, t he A ncient M onuments L aboratory ( AML) h as b uilt o n t he w ork o f E . C rowfoot a nd C . K eepax ( 1975), s o t hat w e a re n ow a ble t o i dentify w ood a nd s ometimes l eather t o

s pecies

e t a l.,

l evel,

a nd d istinguish b etween b one,

h orn a nd i vory

( Cronyn

1 985).

M ineral P reservation o f Organic M aterials I n

o rder

f or

o rganic

m aterial

t o

b e

p reserved,

i t

m ust

b e

i n

c ontact w ith m etalwork t hat i s c orroding r apidly a nd t he s alts p roduced m ust c over t he o rganic m aterial b efore i t i s c onsumed b y m icroo rganisms. T he c orrosion p roducts o n t he m etalwork a re u sually a v ariety o f i ron o xides, b asic c opper c arbonates a nd b asic l ead c arbonates. T he i deal e nvironment f or t he p reservation o f o rganic m aterial i s, t herefore, o ne w hich i s a ggressive t o m etals, s ometimes c onverting t hem t otally t o m inerals. B urials o ften p rovide t his e nvironment, p robably b ecause o f t he p roximity o f a d ecomposing b ody ( Janaway, 1 985). O rganic w ays:

m aterials

c oating,

a re

p reserved

b y

m etal

s alts

i n

o ne

o f

t hree

r eplacement, o r i mpregnation.

C oating. T his i s t he m ost c ommon f orm o f m ineral p reservation. I n t his c ase, t he o riginal o rganic m aterial i s l ightly c oated w ith m etal s alts w hich i nhibit m icro-organism a ctivity. T he m orphological s tructure o f t he o rganic m aterial i s t hus p reserved a nd c an s ometimes b e i dentified u sing c onventional m eans, s uch a s t ransmitted l ight m icroscopy o n t hin-sections a fter t he s alts h ave b een r emoved w ith a s equestering a gent. T his t echnique i s m ainly a pplicable t o w ood o r f ibres p reserved b y c ontact w ith c opper o r l ead c orrosion p roducts t hat a re o ften i n t he f orm o f l arge c rystals ( Fig. 1 ) t hat o bscure t he s urface d etail. I f t he m etal i s a llowed t o c ontinu- c orroding a t a r apid r ate a fter e xcavation, t he f ormation o f l arge c rystals w ill d isrupt

a nd

d eform

t he

p reserved

6 5

o rganic

m aterial.

T he

o rganic

1

3 5,8X * MK

3 O r3 J s 2

3 .8XV 8 0 251M

S 2 8800 P 0 8883

•

4

3

F ig.

8 2,1X M UM

3 222

1 .

M ineral p reserved w ood w ith l arge c rystals o f c opper c orrosion

p roducts. F ig.

2 .

C ross s ection o f w ood p reserved b y c opper s alts t hat h ave b een

l aid d own i n l ayers o f d iffering d ensities. F ig.

3 .

C ross s ection o f S alix s p.

o r P opulus s p.

p reserved b y a l ight

c oating o f i ron o xides. F ig.

4 .

C ross

s ection o f w ood c onsolidated w ith i ron o xides, b ut w ith

t he c ell w all s till i ntact.

6 6

material itself can still warp and collapse out of shape if allowed to dehydrate too quickly after excavation. Under these circumstances, it may be very difficult to identify the type of organic material, not to mention the species. This is a less common type of preservation than coating. Replacement. It is frequently observed in iron corrosion products, but can also be seen to a lesser extent with copper salts. Replacement takes place when the organic material becomes consolidated with corrosion products. The original structure then decays, leaving a negative impression of the organic m a t e r i a l in t h e m i n e r a l. Su f f i c i e n t m o r p h o l o g ical characteristics may be preserved to allow identification of the material, despite the fact that only a negative impression is preserved. In the case of wood, very fine surface detail can be preserved, so that standard microscope keys can be used. With textiles and fleece, the individual fibres have been encapsulated with corrosion products, forming moulds of the fibre casts which may exhibit enough surface detail to make identification possible even when the originals have gone. Replacements in copper salts do not have the same fine detail as those in iron oxides and identification can prove more difficult. In Figure 2, it is possible to see that the copper salts have been laid down in two layers of differing densities, with the more granular one next to the cell wall. Obviously, this granular layer is incapable of reproducing the fine details of features in the cell wall, such as the pit chambers and apertures often seen in the replacements in iron oxides. It is quite common for org anic material such as wood and textiles to be preserved by both coating and replacement on the same sample. Impregnation of porous organic material by metal salts. This is the main type of preservation for bone, antler, ivary, horn and leather. These materials appear unalter�d microscopically, but are fragile and powdery. Preservation by impregnation can occur with both iron and copper salts. Iron oxide-impregnated organic materials tend to be more powdery than those preserved by copper corrosion products. Sample Selection Preservation by metal corrosion products is non-discriminating, so it is essential that the occurrence of preserved organic material is correctly interpreted before destructive techniques are used to take samples for identification of the metal. Any organic material lying adjacent to corroding metalwork may be preserved whether it is part of the object, a piece of organic material that the metal object is lying in or above, or relates to the context in which the metal object has become incorporated. From contexts such as urban rubbish pits, many kinds of organic material may be preserved that are important in interpreting the context, but which have no direct relationship to the object upon which they are preserved.

67

M etalwork

f rom

o rganic m aterial.

B y

g raves

m ay

s tudying

h ave

d ifferent

l ayers

o f

p reserved

t hese i t m ay b e p ossible t o r econstruct

t he o riginal o rganic o bjects b uried w ithin t he g rave. F or t his r eason t he i dentification o f m ineral-preserved o rganic m aterial h as b een m ost b eneficial i n t he i nterpretation o f c emetery r emains, w here, w ith t he a id o f g rave p lans, i t h as b een p ossible t o r econstruct m ost o rganic o bjects f rom t races p reserved o n d ifferent p ieces o f m etalwork. I t i s e ssential t hat t he s pecialist s ees t he o bjects w ith t he m ineral-preserved o rganic m aterial i n s itu, r ather t han b eing p resented w ith s mall f ragments. W ith o ut-of-context s amples, t he s pecialist w ill o nly b e a ble t o s upply t he i dentification o f t he o rganic m aterial, a t b est. I mportant i nformation r egarding t echnology m ay b e l ost t otally, i f k ey f eatures, s uch a s s titches, t he s elvage o f a m ineral-preserved t extile, o r e vidence f or d owels i n j oinery a re a ccidentally t aken f or s amples. A dditionally, i t i s d ifficult, i f n ot i mpossible, t o r econstruct l arge o rganic o bjects f rom t races o n v arious s mall p ieces o f m etalwork. T he e thics o f s ampling a lso n eed t o b e r aised i n c ases w hen a ll t he m ineral-preserved o rganic m aterial h as t o b e r emoved f rom t he m etalwork i n o rder f or i t t o b e i dentified. I f t his c annot b e a voided, t he i dentification r eport s hould b e s upported b y a f ull p hotographic r ecord, i ncluding m icrographs o f a ny p reserved s tructures s o t hat f urther s tudy a nd i nterpretation c an b e m ade i f n ecessary a t a l ater d ate. F or f urther d etails o n t he c ategories o f m aterial p reserved m etalwork s ee E dwards ( AML r eport N o. 4 124 a nd f orthcoming).

o n

S ample P reparation U sing t he S EM o ne c an o bserve t he s urface o f t he s ample i n d etail. S pecimens h ave t o b e m ounted w ith f ractured s urfaces, s ince c utting c an s mear t he d etail o r c ause t he s ample t o b e r educed t o p owder. W hen i dentifying w ood, t he s amples s hould b e m ounted i n t hree planes: cross-section, radial l ongitudinal, a nd t angential l ongitudinal. H owever, w hen d ealing w ith r eplaced w ood i t i s o ften d ifficult t o o btain a c ross-section, s o o ne o ften h as t o t ry t o f ind e nough f eatures t o i dentify t he m aterial f rom t he t wo l ongitudinal s ections. F or o ther m aterials s ection a re u sually r equired.

o ne

l ongitudinal

s ection a nd a c ross-

I n t his s tudy, s amples w ere m ounted o n b rass o r a luminum s tubs w ith s ilver d ag a nd w ere c oated w ith e ither e vaporated g old/palladium o r s puttered g old. U sing a C ambridge S 200, w hich h as a l arge v acuum c hamber, i t h as b een p ossible t o e xamine w hole o bjects, a v ery v aluable f acility w hen l ittle o rganic m aterial i s p reserved a nd s ectioning w ould r emove t he e ntire e vidence. E ven s o, w here p ossible, s ectioned s amples w ere m ounted i n o rder t o l ook a t t he i nternal s tructure.

6 8

A lthough i t w as o ften n ot n ecessary t o c oat s pecimens w ith a c onductive l ayer o f m etal, c oating w as d one w henever p ossible t o i nsure b etter r esolution f or v iewing d elicately p reserved f eatures.

I dentification o f Wood T he a natomical f eatures o f w ood p reserved i n m etal c orrosion p roducts c an b e u sed t o i dentify t he w ood s pecies b y c onsulting a n a tlas ( Schweingruber, 1 982) o r a m icroscope k ey ( Brazier a nd F ranklin, 1 961). T he u se o f a s uitable r eference c ollection c an a id i n e stablishing a ccurate i dentification. A s m entioned e arlier t he d iagnostic f eatures n eed t o b e a ssembled f rom t hree d ifferent p lanes. T he f ollowing l ists p rovide a n i ndication o f w hich s ections e xhibit t he d ifferent f eatures. O n t he w hole t his i s a pplicable t o b oth c oated a nd r eplaced s amples. A g lossary o f t he t erms u sed c an b e f ound i n B utterfield a nd M eylan ( 1980). 1 .

C ross-sections

( Transverse s ections, o r T .S.):

a .

P ore a rrangement, u sually v isible i n s amples p reserved u nder l ight c oatings o f m etal s alts ( Fig. 3 ).

b .

R esin c anals,

c .

A ny u nusual f eatures o f t he r ays, a nnual r ing b oundary.

d .

D istribution o f a xial p arenchyma.

i f p resent,

i n c onifers. s uch a s n oding a t t he

W hen w ood i s h eavily i mpregnated w ith m etal s alts, b ut r etains c ell w alls i ntact, i t i s a lmost i mpossible t o m ake a t axonomic i dentification b ecause o f t he l ack o f t opographical d etail ( Fig. 4 ). I n w ood p reserved b y r eplacement, i t i s i mpossible t o o btain c rosss ections f or s tudy b ecause t he m ineral b reaks u p i nto s mall s plinters s ince t here i s n o c ell w all t o m aintain t he p ore a rrangement. 2 .

R adial l ongitudinal s ections a .

b .

( R .L.S.):

P erforation p lates i n v essels ( however, n ote t hat s calariform p erforation p lates i n r eplaced s amples m ore e asily r ecognised i n T .L.S.). S piral

t hickening

i n v essels

o r

t racheids

( this

c an

a re

a lso

b e s een i n T .L.S.). I n u naltered a nd l ightly c oated w ood t his c an b e o bserved a s r aised l ines o n t he c ell w all ( Fig. 5 ), b ut i n r eplaced m aterial i t a ppears a s d epressions

i n

t he

c ast

( Fig.

6 ).

T his

i s

a n

i mportant

d iagnostic f eature a nd i ts p resence s hould b e c onfirmed b y u sing t he S EM. I n i ncident l ight m icroscopy, o ptical b irefringence c aused b y t he m ineral c omponent m ay g ive t he i llusion o f s piral t hickening. E tching o f t he c ell w all b y f ungal h yphae c an a lso b e m isinterpreted a s a s piral t hickening,

e specially

6 9

a s

t he

h yphae

t end

t o

f ollow t he

6

8

F ig. 5 . S ection o f v essel w ith s piral-thickening, p reserved b y a l ight c oating o f i ron o xides.

f rom

T ilia

s p.

F ig. 6 . S piral t hickening i n i ron o xide r eplaced w ood f rom T ilia s p. T he o riginal c ell w alls h ave d issolved l eaving c asts o f t he p it c hambers i n r elief. F ig. 7 . S ection t hrough a v essel w hich h as b een c olonised b y f ungi. T he w ood, S alix s p. o r P opulus s p., h as b een p reserved b y a c oating o f i ron o xides. F ig. 8 . I ron o xide p reserved w ood ( either S alix s p. o r P opulus s p.). T he v essel h as b een a ttacked b y f ungi, a nd t he e tching o f t he o riginal c ell w all c an b e s een i n r elief.

7 0

s piral o rientation o f c ellulose i n t he c ell w all ( Fig. 7 ). B y S EM e xamination t his w ill a ppear a s t roughs i n t he c ell w all, a nd i n t he r eplaced e xamples t he e tching w ill b e i n r elief ( Fig. 8 ). T his m irrors s piral t hickening. c .

P itting i n t racheids c an b e i ndicative o f c ertain s pecies, b ut s hould n ot b e c onsidered a s d iagnostic.

d .

C ross f ield p its: t he m ost i dentification o f c onifers.

e .

L ongitudinal f eatures o f r ay c ells.

f .

I n r eplaced s amples, t he R .L.S. m ay f rom w hich o ne c an e stablish w hether d iffuse p orous.

3 .

i mportant f eature i n t he

T angential l ongitudinal s ections

b e t he o nly s ection t he w ood i s r ing o r

( T.L.S.):

a .

C ross-section o f r ay c ells a nd t heir a rrangement a mong t he w ood f ibres.

b .

P erforation p lates i n r eplaced v essels, e specially s calariform p erforation p lates w here t he v oids m ay b e c ounted t o o btain t he n umber o f b ars i n t he o riginal p late ( Figs. 9 a nd 1 0).

c .

A xial r esin c anals i n c onifers.

d .

A xial p arenchyma.

I n o rder t o c onfirm t he s pecies o f t he p reserved w ood, i t i s e ssential t hat o ne l ooks a t a ll t hree s ections. H owever, i t i s p ossible t o s uggest t he w ood s pecies f rom t wo s ections; f or h ardwoods t he T .S. a nd T .L.S. a re m ost i ndicative, a nd R .L.S. a re r equired.

w hereas f or c onifers t he T .S.

O ther Materials V arious t ypes o f a nimal t issue s uch a s b one, a ntler, i vory, h orn, l eather, p elts, a nd h airs a re p reserved b y c ontact w ith c orroding m etalwork. A ll t hese m aterials h ave a p orous m atrix w hich c an b e i mpregnated w ith m etal s alts, p reserving t he o rganic s tructure. A s y et, t here a re n o e xamples o f r eplacement o f e xception o f h airs a nd f ibres ( see b elow).

i t

t hese

materials

w ith

t he

A nimal t issues a re m uch m ore d ifficult t o i dentify t han w ood, a nd i s o nly p ossible t o d istinguish t he m aterial u sed r ather t han t o

i dentify t he s pecies o f a nimal f rom w hich i t w as d erived. B ased o n t he w ork i nitiated i n t he A ML, f urther s tudy o n d istinguishing b etween t he d ifferent t ypes o f h ard a nimal t issue w as u ndertaken a s a s tudent d issertation t opic b y G . M oraitou ( 1983). I n t his w ork s he d iscusses t he m orphology a nd d egradation o f t hese

7 1

9

1 0

1 2

1

F ig.

9 .

S calariform p erforation p late

i n

R LS

o f

A lnus

s p.,

p reserved

b y a c oating o f i ron o xides. F ig.

1 0.

S calariform

p erforation

p late

i n

A lnus

s p.

r eplaced

b y

i ron

o xides a nd v iewed i n T LS. F ig.

1 1.

R adial

s ection

o f

e lephant

i vory

e xhibiting

u ndulating

l ines

o f d entinal t ubules. F ig. i vory

1 2.

T angential

s ection

( same s ample a s F ig.

o f

t he

1 1).

7 2

o penings

o f

d entinal

t ubules

i n

m aterials

a nd m akes

s uggestions

o n

t he d iagnostic f eatures t hat m ay b e

u sed.

B one a nd A ntler.

B one c an

s ometimes b e

r ecognised b y

t he p resence o f

H aversian c anals, b oth i n l ongitudinal a nd c ross-sections. I t i s v ery d ifficult t o d istinguish b etween n ormal b one a nd a ntler i n s mall s amples p reserved o n m etalwork a nd f urther r esearch i n t his f ield i s n eeded. I vory. t usks,

T echnically, t he t erm i vory s hould o nly a pply t o e lephant b ut i t i s c ommonly a lso u sed t o d escribe a rtifacts m ade f rom

o ther l arge mammalian w art h og.

t eeth,

I n w ell-preserved

s uch a s w alrus,

s pecimens

i t

i s

h ippopotamus,

n arwhal a nd

e asy t o d istinguish b etween t he

d ifferent t ypes o f d entine ( Penniman, 1 952), b ut i n m ineral-preserved e xamples a ll t hat u sually r emains i s a f ine p owder w ith n o o bvious g rain o rientation. I n t he l atter c ondition, t he u se o f t he S EM c an c onfirm t hat t he m aterial i s d entine b y t he p resence o f d entinal t ubules s een a t m agnifications o f 5 00-1000x. F igure 1 1 s hows a r adial s ection w ith d entinal t ubules a rranged i n u ndulating l ines, w hile F igure 1 2 s hows t heir c ross-section. I t i s a lmost i mpossible, h owever, t o d istinguish b etween t he d ifferent t ypes o f " ivory" o n t he b asis o f s uch f eatures. H orn. U nlike t he p revious t hree m aterials, h orn i s c omposed s olely o f a n o rganic c omponent - k eratin. T hrough b urial, h orn b reaks u p i nto f ine, r ippled l ayers w hich p robably c orrespond t o t he o riginal l ayers d eveloped b y t he a nimal, a lthough t his s tructure i s n ot e asily d istinguished i n f resh h orn. W hen p reserved b y m etal c orrosion p roducts, t he l ayered s tructure i s m aintained a nd i s u sually r ecognised b y t he r ows o f parallel r idges, w hich c an r esemble w ood g rain a t l ow m agnifications ( Fig. 1 3). B y u sing t he S EM, t hough, i t i s o ften e asy t o d istinguish b etween h orn a nd w ood b y t he a pparent l ack o f m orphological f eatures i n h orn a t a ny m agnification. I n i dentifying m ineral-preserved h orn, c omparisons w ere m ade w ith d egraded h orn, r ather t han f resh m aterial, s ince t hat p reserved b y m inerals s alts. L eather

a ppeared

a nd

P elts.

t o h ave b een a ltered b efore

A t

p resent

l eather

c an

g rain p attern o f t he h air f ollicles s urvives,

i mpregnation w ith m etal

o nly

b e

i dentified

i f

a

a nd o ften s uch d etail h as

b een r emoved b y a brasion w hen t he l eather a rticle w as i n u se. T he s tructure i n t he c ross-section o f s kin o ften r emains, h owever,and f urther r esearch m ay p rovide a m eans t o i dentify l eather w hen t he g rain p attern n o l onger s urvives.

m etal

T he h airs o f p elts m ay b e i dentified b y w ell-preserved m oulds i n c orrosion p roducts ( Fig. 1 4), a fter t he o riginal h airs h ave

d eteriorated. T he m oulds u sually e xhibit n egative b ract p atterns w hich a re d iagnostic o f d ifferent a nimals ( Fig. 1 5). H owever, s ome e xperience a nd a ccess t o a r eference c ollection a re r equired b efore o ne c an u se t his f eature a lone t o i dentify t he s pecies o f a nimal i nvolved ( Appleyard, 1 978).

7 3

i

1 3

1 4

1 5

F ig.

1 3.

S tructure o f i ron-oxide p reserved h orn.

F ig. 1 4. C ross-section o f i ron p reserved f leece. T he r esidual h airs h ave s hrunk a nd p reserve l ess s urface d etail t han t he c asts. F ig. 1 5. T he i mpression o f a h air i n i ron c orrosion p roducts, w ith t he s cale p attern o f t he o riginal c learly p reserved.

7 4

T extiles a nd F ibres. f ibres

i n

a

C orrosion products c an e ncapsulate t he i ndividual

t extile

a nd

s imultaneously

d istinguished macroscopically. pattern o n d istortion. I n

a

b y u sing

t he

Q uite s urprisingly,

m ineral-preserved

l ightly-coated

c orrosion

a llow

may

r emain

f ibres

c an

b e

a gents

t o

b e

t he o verall w eave

t extile

s amples,

s equestering

w eave

f airly

e xtracted

s uch a s E DTA,

f ree

f rom

o f

t he

a nd b e i dentified

u sing t ransmitted l ight m icroscopy.

W ith t extiles preserved o n h eavily

c orroded

t o

f ibres

o bjects, f rom

i t

t heir

may

b e

e asier

moulds

i n

t he

u se

S EM

t echniques

c orrosion

i dentification o f a nimal f ibres s ee Appleyard f ibres s ee C atling a nd G rayson ( 1982).

t o

p roducts.

( 1978),

i dentify F or

a nd

t he

f or v egetal

S u mary U nder c orroding Most

o f

c ertain

c onditions

metalwork t his

u naltered

a nd

work

t he

c an

material.

b e

i dentifying

u ndertaken

H owever,

d istinguishing between bone o f

o rganic

l eather

materials

r esultant

u sing

t here

a nd

f rom

s tructures

preserved b e

e stablished

i s

a ntler,

a re c an

s cope

f or

b y

i dentified.

k eys more

f or

t he

work

i n

a nd l ooking a t t he possibility

c ross-sections

r ather

t han

t he

r arely

preserved g rain patterns. U sing

t he

S EM

t o

make

s pecialist o rganic d etails,

r ather

material. t his

w ork

t han

a ccurate

a n

optical

microscope

i dentifications

I n

c ombination

f orms

t he basic

w ith

t he

o f

e nables

t he

mineral-preserved o f

t echnological

r ecord o f perishable

s tudy

r aw materials

u tilised i n a ncient m etalworking periods.

Acknowledgements T he

work

presented

i n

t his

paper

was

u ndertaken

a t

t he

Ancient

Monuments Laboratory o f t he H istoric B uildings a nd Monuments C ommission f or

E ngland,

a nd

t he

a uthor would l ike t o t hank t he C ommission f or i ts

c ontinued s upport o f t his r esearch.

References Appleyard,

H .M.

2 nd e dition. B iek,

L .

1 978.

L eeds:

1 963.

G uide t o t he I dentification o f A nimal F ibres.

W IRA .

Archaeology

a nd

t he

M icroscope.

L ondon:

L utterworth

P ress. B razier,

J .D.

a m icroscope L ondon:

k ey.

F orest

G .L.

1 961.

P roducts

I dentification o f hardwoods:

R esearch

Laboratory

B ulletin

4 6:

H .M.S.O.

B utterfield, o f Wood.

a nd Franklin,

B .G.

a nd M eylan,

2 nd e dition.

L ondon:

B .A .

1 980.

T hree-Dimensional S tructure

C hapman a nd Hall.

7 5

C atling,

D .

a nd

F ibres.

L ondon:

C ronyn,

J .,

G rayson,

J .

1 982.

T he

I dentification

o f

V egetable

C hapman a nd Hall.

P ye,

E .

a nd

Watson,

J .

1 985.

T he

r ecognition

a nd

i dentification o f t races o f o rganic materials i n a ssociation w ith m etal artifacts.

I n

L aboratory,

pp.

P hillips,

2 4-27.

P .

L ondon:

( ed .),

T he

Archaeologist

C BA R esearch R eport N o.

a nd

t he

5 8.

E dwards, G ., f orthcoming. G uidelines f or d ealing w ith material f rom s ites w here o rganic r emains h ave b een p reserved b y m etal c orrosion products. I n E vidence P reserved i n C orrosion P roducts. L ondon: UKIC O ccasional P aper. J anaway,

R .C.

materials

i n

A lso a vailable a s a n AML r eport, 1 985.

m etal

i nhumation g raves.

D ust

t o

a rtefact

d ust:

c orrosion

t he

N o.

4 124.

preservation

products

S cience a nd Archaeology 2 7:

w ith

B one,

G .

A ntler,

1 983. H orn,

S tructure, a nd

I vory.

t extile t o

2 9-34.

K eepax, C . 1 975. S canning e lectron m icroscopy o f wood i ron c orrosion products. J . Archaeol. S ci. 2 : 1 45-150. Moraitou,

o f

r eference

D eterioration, U npublished B .

a nd

S c.

r eplaced b y

I dentification

d issertation,

o f

U niv.

L ondon. P enniman, a nd

T .K.

a ntler.

Museum,

U niv.

S chweingruber,

1 952. O xford:

P ictures O ccasional

o f

i vory a nd

P aper

o n

o ther

a nimal t eeth,

T echnology,

5 ,

P itt

bone

R ivers

O xford. F .H.

1 982.

M icroscopic

Wood

S wiss F ederal I nstitute o f F orestry R esearch.

7 6

Anatomy,

2 nd

e dition.

P ART I I :

POTTERY

7 7

I DENTIFICATION O F S UBSOIL I NCLUSIONS I N P OMONA C ERAMICS D onald J . B lakeslee a nd R ichard K . D unn

I ntroduction T his p aper i llustrates t he u se o f t he S EM i n c onjunction w ith t hin-section a nalysis i n r esolving a p roblem i nvolving p rehistoric c eramics. P revious d escriptions o f P omona c eramics f rom t he e astern G reat P lains o f N orth A merica d isagree o n t he n ature o f t he t empering m aterial u sed. R ecent r eports e mphasize t he w ide r ange o f materials s een - u p t o 2 5 d ifferent c ombinations i n o ne s tudy - a nd v arious a nalysts r eport c onflicting r esults f rom t he s ame a ssemblages. T he s tudy r eported h ere c ombined S EM e xamination o f f reshly b roken s herd e dges w ith o ptical e xamination o f g round e dges a nd t hin s ections. T he r esults i ndicate t hat P omona c eramics r epresent a n u nusual a daptation t o a p articular e nvironment, t he O sage C uestas p hysiographic p rovince. F requently, t he c lays w ere u sed w ithout t he a ddition o f t emper a nd w ith a m inimum o f p reparation. S ubsoil s tructures, i ncluding p eds, c oncretions a nd c lay-lined v oids mimic a v ariety o f t emper t ypes, a nd most s herds c ontain a c ombination o f t hese s ubsoil i nclusions. T he n ature o f t he c lay a nd t he p resence o f t he i nclusions p recluded t he n ecessity o f p urposefully a dding t emper. L ack o f a ging o f t he c lay t o r emove o rganics m andated a l ow f iring t emperature.

Background T he P omona v ariant ( originally t he P omona f ocus) i s a n e xpression o f t he P lains V illage t radition o f c entral N orth America. S ites o f t his c omplex d ate t o A .D. 9 50-1400. T hey a re f ound i n t he O sage C uestas p hysiographic p rovince o f e astern K ansas a nd w estern M issouri ( Fig. 1 ). T he s ites c onsist o f t he r emains o f l ightly-built w attle a nd d aub h ouses w ith a ssociated r ock-filled h earths, s torage p its a nd a ctivity a reas ( Blakeslee a nd R ohn, 1 986; B rown, 1 984; R ohn a nd D aniel, 1 984; W itty, 1 967, 1 981). * The c ontents o f t he s ites a re i ndicative o f am ixed e conomy t hat i ncluded h orticulture, h unting a nd g athering. T he P omona v ariant i s b ordered b y o ther u nits o f t he P lains V illage t radition. T o t he n ortheast i s t he S teed-Kisker c omplex, i n t he K ansas C ity a rea. T he c eramics o f t his u nit, h eavily i nfluenced b y t he M ississippian s tyles o f t he e ast, a re u sually t empered w ith c rushed s hell. T he N ebraska p hase, w hich l ies n orth o f t he P omona r ange, a lso h as s ome s hell-tempered p ottery, b ut t he b ulk i s t empered w ith c rushed g ranite. T o t he n orthwest i s t he S moky H ill p hase, a lso w ith s ome s hell t empering, b ut w ith a m ajority o f g rog ( crushed p ottery) t emper. S outh o f t he P omona a rea a re u nits o f t he C addoan t radition, w hose p ottery i s u sually t empered w ith c rushed b one. T he v arious c ultural g roups m entioned,

a nd o thers o f t he s ame t ime

p eriod, h ave a t endency t o g rade i nto o ne a nother n ear t heir b oundaries. T ransitional s ites, i n w hich a ttributes o f c eramics a nd o ther a rtifacts a re b lended, a re c ommon. T hus, i t i s n ot s urprising t o l earn t hat s ome P omona s ites y ield v essels w ith s hell, c rushed g ranite,

7 9

N E I A _

o v -

• \ H i l lsda le L ake

CN

K S

OK

_

— 1 . I 'M O I

AK

Caddban A rea

F ig.

1 .

L ocation o f t he P omona v ariant a nd c ontemporary c omplexes.

8 0

g rog, o r b one t emper ( Witty, 1 967: 4 -5). W hat s ets P omona a part f rom t he o thers i s a n a pparent l ack o f a p redominant t emper t ype i n i ts c ore a rea. P omona p ottery i s a s imple, g enerally u ndecorated, u tilitarian w are. J ars a re s mall a nd g lobular, u sually w ith a h igh, n early v ertical r im . T hey w ere f ormed b y l ump-modelling, f ollowed b y s haping a nd t hinning u sing t he p addle a nd a nvil t echnique. I n m any i nstances, t he a nvil a ppears t o h ave b een t he p otter's h and. T he p addle w as l oosely w ound w ith c ordage ( in s ome c ases, n etting), w hich h as l eft i mpressions o n t he e xterior s urfaces o f t he j ars. T he v essels w ere f ired a t r elatively l ow t emperatures. E vidence f or l ow f iring t emperatures i ncludes t he s oftness o f t he s herds ( averaging j ust a bove 2 o n M ohs' s cale o f h ardness) a nd g ray c ores v isible i n s herd c rosss ections i ndicating u nderfiring. E xperimental v essels m ade f rom O sage C uesta s ubsoils a nd f ired i n a s mall s urface c ampfire w ere h arder t han P omona s herds. A c eramist w ho e xamined a s et o f P omona p ottery c ame t o t he s ame c onclusion a bout f iring t emperature, i ndependently ( Wright, c ited i n W ilmeth, 1 970: 2 7). T he l ow f iring t emperatures y ielded c eramics t hat w ere r eadily a braded a nd e roded a fter d eposition i n t he g round. A s a r esult, m ost s herds f rom P omona s ites h ave m ore o r l ess r ounded e dges. T he h ighly p orous s herds, o nce d eposited, a re s ubject t o t he s ame f orces t hat f orm t he s urrounding s ubstances m ay b e a dded t o o r l eached f rom t hem.

s oil,

a nd

v arious

T he P omona v ariant i s l imited i n i ts d istribution t o t he O sage C uestas p hysiographic p rovince. T his r egion c onsists o f r olling h ills a nd e ast-facing e scarpments ( Fenneman, 1 931). T he v egetation c onsists o f t allgrass p rairie c ommunities. T he d istribution o f t rees i s l imited t o g allery f orests a long s treams, a nd t o g roves o n e scarpments a nd o n t he f ew h illtops w here t he b edrock i s s andstone. A ll s treams e xcept t he l argest r ivers a re e ntrenched, a nd t he r egion i s s outh o f t he a rea t hat w as g laciated d uring t he P leistocene. T he l and s urface i s t hus r elatively o ld, w ith h ighly d eveloped s oil h orizons. T he c limate i s c ontinental, w ith a w ell-marked w et s eason i n t he s pring a nd d ry s ummers. T he s oils a re g enerally a cidic, a nd b one i s s eldom p reserved i n t he a rchaeological s ites. T he r egion i s d ominated b y m ollisols t hat h ave a n a rgillic ( clay r ich) h orizon. T he W oodson s oil t hat i s w idespread i n t he u plands i s h eavy, a nd t he z one f rom 1 0 t o 3 0 c m b elow t he s urface i s f requently r ecorded a s h aving a c lay t exture ( Soil C onservation S ervice, 1 979: 8 7). T his i s t he f inest o f a s eries o f e leven t exture c lasses f or s oil a nd i s i ndicative o f a n e xtremely c layr ich z one ( Soil C onservation S ervice, 1 979: 4 6). T his i lluvial h orizon ( zone o f c lay d eposition b y s oil f ormation p rocesses) i s p lastic e nough t o f orm p ottery w ithout e xtensive a ging o r p rocessing o f t he c lay. W oodson a nd o ther c lay-rich s oils i n t he r egion c ontain n umerous f errous-manganese o xide c oncretions a nd b locky t o p rismatic p eds.

T he P roblem T he l iterature r egarding P omona c onsistent. T he o riginal d escription

8 1

p ottery i s f ar f rom c lear a nd a nd d efinition o f P omona w are i s

b y W ilmeth ( 1970: 2 6-28). H e d escribes t he p aste a s " a f airly f ine b ut i mpure c lay, [ that] w as p robably u sed w ithout m uch w orking, o ften r esulting i n a r ather l umpy a ppearance." H e a lso s uggests, h owever, t hat t he t empering m aterial w as g rog ( crushed s herds), w hich h e d escribed a s s mall i nclusions o f t he s ame t exture a nd h ardness a s t he p aste. L ater d escriptions o f t empering m aterials d o n ot c orrespond c losely t o W ilmeth's. W itty ( 1981: 8 0) s tates t hat P omona w are c ontains " sparse i nclusions o f i ndurated c lay, w eathered s hale a nd o ccasional c rushed b urned b one f ragments." f requent m ention o f i ndurated c lay o r s hale,

O ther d escriptions m ake a nd many c ombinations o f

d ifferent t emper t ypes h ave b een r ecorded. R ohn a nd D aniel ( 1984: 1 4, 6 7), o n t he o ther h and, a gree w ith o ne o f W ilmeth's a ssertions, t hat P omona p ottery i s e ssentially u ntempered b ut w ith i nclusions o f i ron o xide, q uartz s and, i ndurated s hale p latelets, a nd o ccasional p ieces o f o rganic m atter. I n a r ecent s urvey o f P omona a rchaeology, B rown ( 1984) r ecorded 2 5 d ifferent t emper c ombinations. P rimary i ngredients l isted b y h im i nclude s and, s herd ( grog), l imestone, b one, s hell, g ranite, c alcite a nd n o t emper. H is s hell t emper c ategory i ncludes b oth t hose s herds w hich r etain s hell p articles a nd t hose w hich e xhibit f lat p arallels ided v oids, p resumably l eft b y s hell p articles l eached f rom t he s herd b y a cidic g roundwater. S ome a uthors p refer t o u se t he t erm " cell t emper" i n t he a bsence o f p roof o f t he o rigin o f t hese f eatures ( Bell a nd G ilmore, 1 936: 3 18). S ince s ome P omona s herds c ontain s hell t emper a nd b ecause t he s oil e nvironment i s f requently a cidic, i t i s l ikely t hat a t l east s ome o f t he f lat c ells s een i n P omona s herds w ere p roduced b y l eaching o f s hell. O ther s ources a re p ossible, h owever. W itty s uggests t hat m ost d erive f rom f laky, i ndurated c lay u sed a s t emper. " Many s herds w eather t o h ave t he a ppearance o f t he ' cell t emper'. T his i s f ormed b y t he f laky c lay i nclusions d issolving o ut o f t he p aste" ( Witty, 1 967: 2 ). W hy c lay f lakes w hich d id n ot d issolve w hen a dded t o a m oist p aste s hould l each o ut a fter f iring i s n ot e xplained . S till o ther f rom t he b inocular

s ources

f or

t he

c ells

a re p ossible.

W hen

t he s herds

H illsdale L ake ( Fig. 1 ) w ere e xamined w ith a l ow p ower o ptical m icroscope, s everal l ines o f e vidence s uggested

m ultiple o rigins. S ome s herds c ontained b oth e mpty c ells a nd a f ew c ells t hat r etained r emnants o f s hell t emper. O n o ther s herds t he v oids w ere e ntirely e mpty, w ith n one o f t he s herds f rom a w hole s ite e xhibiting a ny s hell p articles. I n s ome r are c ases, a f ew o f t hese e mpty

c ells

w ere

s urrounded

b y

a reas

o f

r educed

( blackened)

p aste.

T his i mplies t hat a t l east s ome c ontained c ombustible o rganic m aterial t hat t ook u p t he a vailable o xygen a t t he t ime t he p ot w as f ired. S till o ther s herds h ad f lat c ells l ined o r c ompletely f illed w ith l ighter c olored m aterial. A s t his m aterial d id n ot r eact w ith h ydrochloric a cid, i t c annot b e s hell t emper. S ometimes, t his l ighter m aterial r esembles c lay, a nd i t i s p robably w hat W itty i dentified v ariously a s i ndurated c lay a nd w eathered s hale. L eaching, h owever, w ould p roceed f rom t he e xterior o f a s oluble p article t oward t he c enter, n ot t he r everse. H ence t he c ells

8 2

t hat a re l ined w ith t his m aterial c annot r esult f rom t he d issolution o f i t, a nd W itty 's e xplanation o f t he o rigin o f t he e mpty c ells b y t his p rocess a ppears w eak.

R ohn

P rior t o t he H illsdale L ake p roject ( Blakeslee a nd R ohn, 1 986; a nd D aniel, 1 984: 6 7), n one o f t he d escriptions o f P omona p ottery

c orrectly i dentified t he f errous-manganese o xide c oncretions w hich t his s tudy s hows a re c ommon i nclusions i n t he p aste. T hese d erive f rom l ocal s ubsoils. T hose o bserved v aried i n s ize f rom 0 .1 mm t o 1 .9 m m i n d iameter a nd r ange i n c olor f rom b lack t o r ed. P resumably, t he c oncretions, w hich o ccur d ensely i n s ome s herds, w ere o ften i ncorrectly i dentified i n e arlier r eports a s s ome k ind o f t emper. O n h eavily e roded s herds, t hey a re d ifficult t o d istinguish f rom g rog u nless a f reshly b roken e dge i s e xamined. T he v ariety o f s ubstances f ound i n P omona c eramics a nd t he v arying i nterpretations o f t hem c ombine t o m ake u niform r eporting d ifficult. T here i s a g reat p otential f or b oth i nter- a nd i ntra-observer e rror, e ven i n t he f ace o f t he m ost c areful a nalysis. I n t he r eport o f t he H illsdale L ake p roject i nter-observer e rror w as e liminated b y a ssigning a s ingle t echnician t o i dentify a ll o f t he p ottery f rom t he v arious s ites, w hile i ntra-observer e rror w as m inimized b y u sing t emplates f or a ll d iscrete t raits ( Blakeslee a nd R ohn, 1 986: 1 43-144). A ll o f t he s herds l arger t han 7 m m i n d iameter f rom e ach s ite w ere e xamined w ith a b inocular m icroscope. S imilarly, B rown ( 1984) a nalyzed s amples f rom v arious l ocalities s olely b y h imself i n o rder t o e liminate i ntero bserver e rror f rom h is s urvey. W here c omparisons o f t he a nalyses o f t he p ossible, t he r esults a re s hockingly d ifferent. ( 1986: 7 34-735) r eport 3 5% u ntempered, 4 2% s and t emper,

a nd 4 % g rog

t emper

t wo o bservers a re B lakeslee a nd R ohn t empered, 9 % s hell

i n t he 3 86 s herds f rom s ite 1 4MM213.

B rown

( 1984: 1 56) e xamined a s ample o f 1 13 o f t hese s herds a nd f ound 7 .1% u ntempered, 0 % s and t empered, 0 .9% g rog t empered, a nd 9 1.2% s hell t empered. S imilarly, R ohn a nd D aniel ( 1984: 1 3-16) f ound a ll b ut f our o f t he 3 2 s herds f rom s ite 1 4M 1 421 t o b e u ntempered, w ith t hree e xamples o f b one a nd o ne o f s hell t emper. B rown ( 1984: 1 56), o n t he o ther h and, f ound 7 7.8% o f a s ample o f n ine s herds t o b e s hell t empered, e ach w ith n o t emper a nd a c ombination o f b one a nd g rog t emper.

a nd o ne

O bviously, t here i s a s erious p roblem h ere, o nly a s mall p art o f w hich c an b e a ttributed t o s ample s ize. O ne p roblem h as t o d o w ith w hether a ll e mpty c ells, r egardless o f n umber a nd s ize, a re i dentified a s t he r emains o f s hell t emper. A nother i s t he q uestion o f w hether v arious p articles a re p urposefully a dded o r a re p art o f t he p aste o f a n o therwise u ntempered w hether a s herd w ith

v essel. S till a nother i s t he d etermination o f a n a ngular, l umpy a ppearance o n a f reshly b roken

e dge h as g rog t emper o r m erely a p oorly m ixed p aste. T he

s tudy

p resented

h ere

a llows

r esolution

o f

m ost

o f

t hese

p roblems a nd a dditionally p rovides a n e xplanation o f t he n ature o f P omona c eramics. F irst, h owever, i t i s n ecessary t o r eview t he n ature o f

c eramics

a nd

t he

m aterials

a vailable

m anufacture t hem.

8 3

t o

t he

P omona

p eople

t o

C lays, Nonplastics, a nd S ubsoils C eramics

a re

c omplex

s ubstances

t hat u sually i nclude b oth p lastic

a nd n onplastic m aterials. T he p lasticity o f t he w et c lay a llows v essels a nd o ther o bjects t o b e s haped. N onplastics m ust f requently b e a dded, h owever, t o r educe p lasticity. T he m ore p lastic a c lay i s, t he g reater t he s hrinkage d uring d rying a nd f iring a nd h ence t he g reater t he r esulting p otential f or c racking d uring t hese p rocesses. T he p resence o f n onplastics " counteracts s hrinkage a nd f acilitates u niform d rying, t hus r educing s train a nd l essening t he r isk o f c racking" ( Shepard 1 954:

2 5).

N onplastics c an b e a dded p urposefully o r m ay a lready b e p resent i n t he c lay. I n t he f ormer i nstance, t hey a re c alled t emper; i n t he l atter, i nclusions. S ome c lays w ill d ry a nd f ire s atisfactorily w ithout t he a ddition o f t emper. F requently t hese a re r esidual c lays t hat c ontain a s ubstantial n umber o f i nclusions ( Shepard, 1 954: 5 3). G enerally, c eramics a re f ormed f rom e ither o f t wo b asic c ategories o f c lay. R esidual c lays a re t hose t hat r emain i n c ontact w ith t heir p arent m aterial o f i gneous r ock. S uch c lays o ften r etain o ther m inerals f rom t he p arent r ock, i .e., i nclusions ( Shepard, 1 954: 1 1). S econdary o r s edimentary c lays h ave b een t ransported f rom t heir p oint o f o rigin b y w ater. F requently, t he i nclusions a re r emoved d uring t his p rocess, l eaving a p ure c lay ( Shepard, 1 954: 1 1). H ence, b ecause o f i nclusions a lready p resent, r esidual c lays a re m ore l ikely t o b e u sed w ithout t emper t han a re s edimentary c lays. T here i s a t hird p otential s ource o f c lays t hat w as o nly r arely u sed f or c eramics. I t i s s o r are a s a s ource t hat i t i s n ot d iscussed b y S hepard ( 1954) i n h er c omprehensive v olume, C eramics f or t he A rchaeologist. T his i s s ubsoil c lay f ormed d uring t he p rocess o f s oil d evelopment. W hile m any s oils h ave a n a lluvial o rigin, c lay d eposits w ithin t hem m ay n ot b e p roduced b y t he s ame f orces t hat s hape t he a lluvial c lays d iscussed b y S hepard. C hemical a nd m echanical p rocesses s lowly r emove c lay p articles f rom t he A h orizon, o r e luvial z one o f a s oil, a nd d eposit t hem f arther d own i n t he s oil, i n t he i lluvial z one. I n s ome s oils, e nough c lay a ccumulates t hat t he i lluvial z one i s t ermed a n a rgillic h orizon ( Soil C onservation S ervice, 1 975: 1 9). N ot a ll s oils e nd u p w ith c lay-enriched a rgillic z ones, b ut i n s ome, t he c oncentrations a re r emarkable. A s oil t hat h as o nly e leven p ercent c lay i n i ts c omposition n ear t he s urface m ay b e 5 0 p ercent c lay o nly 1 8 t o 3 6 c m b elow t he s urface ( Soil C onservation S ervice, 1 975: 2 2). F actors i nvolved i nclude t ime, c limate, s oil a cidity a nd t ype o f c lay. O ld s oils ( i.e., o n o ld, s table l and s urfaces) h ave h ad m ore t ime f or t he c lay t o b e l eached f rom t he e luvial h orizon a nd t o b e r edeposited i n t he i lluvial h orizon. A c limate w ith a w ell-defined d ry s eason s eems t o e nhance t he p rocess ( Soil C onservation S ervice, 1 975: 1 9-21), w hile c arbonates i n t he s oil t end t o i nhibit t he p rocess. M ontmorillonite c lays a re t ransported m ore r apidly t han o ther c lay m inerals ( Soil C onservation S ervice, 1 975: 1 9-21).

s oils

O ther p rocesses t hat a lso o ccur i n s oils a re p ertinent h ere. A ll -e volve a " structure" o ver t ime, p roducing a p atterned s et o f

s olid p articles a nd v oids

( Brewer,

1 964:

8 4

1 3).

I ncluded a mong t he s olid

p articles a re p eds, n aturally o ccurring a ggregates o f s oil p articles ( Soil C onservation S ervice, 1 975: 4 74). T hese c an b e p laty, c olumnar, g ranular, b locklike o r p olyhedral i n s hape. S ometimes t hey a re d elimited b y t hin c lay f ilms o n t heir s urfaces ( Soil C onservation S ervice,

1 979:

4 6).

P eds d iffer f rom c lods, l umps f ormed b y d isturbance, a nd f rom c oncretions, w hich a re c emented t ogether c hemically. C oncretions d o o ccur i n s ome s ubsoils. T hose f ormed i n a lkaline s oils a re c alcareous, w hile t hose t hat f orm i n a cidic s oils a re c emented w ith i ron a nd/or m anganese o xides. T he l atter t ype s pherical p ellets o f v arying s ize.

c onsists

o f

b lack

t o

r eddish

A lso t o b e f ound i n s ubsoils a re o rganic m aterials a nd s everal k inds o f v oids. S ome o f t he l atter a re f ormed b y p lant r oots, o thers b y b urrowing i nsects, a nd s till o thers, s uch a s d rying c racks a nd s paces b etween p eds, a re t he r esult o f m echanical a nd c hemical processes i n t he s oil ( Brewer, 1 964: 1 79-196). I n c ertain e nvironments, s ubsoil v oids b ecome l ined w ith f ine c lay o r o ther m aterials. 2 06-231).

T he

r esultant

c oatings

a re

c alled

c utans

( Brewer,

1 964:

T he e xtent t o w hich p ottery m ade f orm s ubsoil c lays w ill r etain t hese f eatures d epends p rimarily o n h ow m uch t he c lay i s p rocessed p rior t o t he m anufacture o f c eramic o bjects. G rinding t he c lay w ill d estroy p eds a nd c oncretions a nd w ill r emove t he v oids. T horough k neading o f t he c lay i n t he a bsence o f g rinding w ill d estroy p eds a nd u nlined v oids b ut n ot c oncretions o r s ome c utans. I lluviation c utans, formed f rom c lay p articles i n s uspension, c onsist o f p arallel a lignments o f t ightly p acked c lay p articles. A s a r esult o f t heir s tructure, t hey a re f ar l ess s oluble i n w ater t han t he r andomlyo riented c lay particles i n t he g eneral s oil m atrix. T hey a re, t herefore, r esistant t o d estruction w hen t he s ubsoil c lay i s m ixed w ith w ater t o c reate a c eramic p aste. E xperimental m ixing o f u nground s ubsoil c lays s hows t hat s ome d issolve r eadily i n w ater, w hile o thers m ust b e s oaked f or l ong p eriods b efore a ll t he p eds d issolve.

d ays

A ging ( adding w ater t o c lay a nd l etting i t s tand f or a p eriod o f t o w eeks) w ill r emove l arge o rganic m atter t hrough d ecomposition.

M ost o f t he o rganic m aterial a nd m ethane) w hich e scape p erformed s o t hat t he g asses w ill n ot b loat t he c lay w hen

i s t hus c onverted t o g ases ( carbon d ioxide i nto t he a ir. T his p rocess i s u sually c reated b y c ombustion o f o rganic m aterials t he v essel i s f ired. W hen i t b loats, c lay

a ctually f oams u p, l eaving a s coria-like a ppearance. A ging s hould a lso w eaken o r d estroy t he p ed s tructure a s t he c lay c utans s lowly d issolve.

H ypothesis A p ossible e xplanation f or t he u nusual n ature o f P omona c eramics i s t hat

t he

P omona

p eople

u sed

t he

l ocal

s ubsoil

c lays

t o

m anufacture

t heir v essels. T he e nvironment i n w hich t hey l ived c ontained u nusually r ich s ubsoil c lays b ecause o f a c ombination o f f actors, i ncluding a s table o ld l and s urface, a d ry s eason, a nd a cidic s oil c onditions. T he c lay-rich c lay

s ubsoils

o ther

t han

w ere

t he

a pparently u sed w ithout a ny p reparation o f t he

a ddition

o f

w ater

8 5

a nd

s ome

m inimal

p reliminary

k neading. I n t his w ay, t he f errous-manganese o xide c oncretions w ere a lmost a lways i ntact, a nd p eds a nd c utans h ave o ccasionally b een p reserved i n t he p ottery. T he p resence o f n umerous i nclusions m eant t hat n o a ddition o f t emper w as n ecessary. L ack o f a ging r equired t hat t he p ottery b e f ired a t r elatively l ow t emperatures. I t i s h ypothesized h ere t hat P omona p ottery w as n ormally f ormed f rom u ntempered s ubsoil c lays a nd f ired a t l ow t emperatures. W hile i t i s d efinitely t he c ase w ith s hell, g rog, b one,

t hat s ome P omona s ites y ield s herds t empered o r g ranite, t hese c an b e a ttributed t o c ontact

w ith n eighboring c ontemporary s ocieties. T his h ypothesis i mplies t hat m any o f t he i dentifications o f n onplastic m aterials i n P omona c eramics a s v arious s orts o f t emper a re i ncorrect a nd t hat t hese a re, i n f act, i nclusions d erived f rom t he s ubsoil s ources o f t he p aste. S herds i n w hich t he p aste r etains b locky o r p rismatic p eds w ill b e s imilar i n a ppearance t o t hose w ith g rog t emper. C oncretions a lso c an b e m istaken f or g rog. T his i s s o b ecause s ome c oncretions h ave n early t he s ame t exture a s t he s oil f rom w hich t hey w ere f ormed, a nd s herd t emper i s a lso u sually s imilar i n t exture t o t he s urrounding p aste. B ecause g rog i s a ngular i n o utline, h owever, i t c an b e d istinguished f rom c oncretions, w hich t end t o b e r ounded. S ome p ieces o f g rog a re d erived f rom t he o uter o r i nner s urfaces o f v essels w hich m ay r etain d iagnostic f eatures t hat a llow t hem t o b e d istinguished f rom a ngular p eds. V oids p resent i n t he s ubsoil m ay b e p reserved i n t he s herds, b ut u sually i n d istorted f orm . T he p addle a nd a nvil t echnique o f m anufacture w ill f latten m ost p reviously e xisting v oids t o a l enticular s hape. E xceptions m ay b e v oids l ined w ith r elatively i nsoluble m aterials, t hose c ontaining r igid o bjects, a nd v oids i n p eds t hat d o n ot d issolve c ompletely. F lattened s ubsoil v oids a nd v oids l eft b y t he c ombustion o f l eaf f ragments m ay b e m istaken f or s paces l eft b y l eached s hell t emper. O ther c ombustible o r l eachable m aterials m ay l eave v oids o f v aried s hapes.

o f

A rgillic c utans l ining v arious v oids c an b e m istaken f or p articles s hale. I f t he v oid i s n ot c ompletely f illed w ith t he c lay l ining,

t he r esultant h ollow p article w ill g ive t he i mpression o f a n o bject t hat i s d issolving f rom t he c enter t o t he o utside. C utans c an b e distinguished i n t hin s ection w ith a p etrographic m icroscope ( Fitzpatrick,

1 984:

2 07-222).

S amples a nd Methods A

s et

o f

P omona

s herds

w ere

e xamined

w ith

t he

S EM

i n

o rder

t o

c larify t he n ature o f t he a plastic m atter a nd v oids i n t hem a nd t o c ompare t hem t o a n u ndisturbed s ubsoil. A ll b ut o ne o f t he s herds a re f rom t he P omona c omponent a t s ite 1 4MM213, a t H illsdale L ake, i n e astern e rror

i s

K ansas. k nown

T his

i s

o ne

o f

t he

s ites

f or

w hich

i nter-observer

t o h ave b een a s evere p roblem w hen o ptical a nalysis w as

p erformed. T he s ingle e xception i s p eriod a ffiliation f rom s ite

a g ranite-tempered s herd 1 4M 1 1551, w hich i s a lso

8 6

o f W oodland l ocated a t

H illsdale

L ake.

I t

w as

i ncluded t o p rovide

a c omparison b etween t he

P omona s herds a nd a s herd k nown t o h ave b een p urposefully t empered. S ince g ranite i s n ot l ocally a vailable i n t he v icinity o f H illsdale L ake, i t w as a lso l ikely t hat t he v essel w as m ade e lsewhere a nd t hat t he p aste o f t he s herd w ould d iffer s omewhat f rom t he P omona p astes. T he s oil s ample c hosen f or e xamination i s a c lear e xample o f t he u ndisturbed f ormation o f p eds i n a s ubsoil c ontext. I t c onsists o f a p lug o f s oil t aken f rom t he m arrow c avity o f t he t ibia o f a w hite-tail d eer ( Odocoileus v irginianus). c omponent o f L ate A rchaic a ge

a t

T he b one i s f rom a N ebo H ill p hase s ite 1 4MM1C d ated t o 3 885 + /- 1 35

y ears B .P. ( UGa-4084) a nd 4 020 + /- 9 0 y ears B .P. ( UGa-4085). T he a nimal b one f rom t his c omponent h ad b een b roken, p ossibly f or m arrow e xtraction, a llowing i nfiltration o f s oil i nto t he m arrow c avity. I nside t he b one, t he s oil w as e xposed t o a pproximately t he s ame p rocesses t hat p roduce p eds i n n atural c onditions ( with t he e xception, of c ourse, o f t he p artial c hemical b uffering p rovided b y t he s urrounding b one). B locky p eds, v isible t o t he n aked e ye, w ere p resent b oth i n t he s oil f rom s urrounded t he b one. T wo

P omona

s herds

t he

w ere

m arrow

c avity

s elected

f or

a nd

i n

t he

c omparison

m atrix

w ith

t he

t hat

s oil

s ample. O ne w as i dentified a s h aving g rog t emper b y e xamination o f a f reshly b roken e dge w ith a 1 0X h and l ens. T he o ther w as t entatively i dentified b y s imilar e xamination a s h aving a b locky paste t hat r esulted f rom i nadequate m ixing. A lso

c hosen

f or

c omparison w ith

d aub f rom s ite 1 4MM213.

t he s ubsoil s ample w as a p iece o f

T he d aub o riginated f rom a h ouse i n t he P omona

c omponent. T he c lay f or t he d aub i s t hought t o b e d erived f rom a s hallow b asin-shaped p it i n w hich w ater w as a dded a nd t he r esultant m ud m ixed b y t rampling. S uch p its a re f requently a ssociated w ith P omona h ouses. I t w as e xpected t hat t he d aub w ould l ack a ny p ed s tructure, b oth b ecause o f i ts n ear-surface o rigin a nd b ecause o f t he m ixing i n t he p it. T wo P omona s herds w ere s elected f or e xamination o f t he f lat c ells. O ne, 1 4MM213-146, c ontains c ells t hat a re l ined w ith a l ighter-colored s ubstance t han t he s urrounding p aste. T he s econd s herd l acked a ny v isible l ining o f t he f lat c ells, b ut e xhibited s everal f errousm anganese o xide c oncretions a nd o ne r eadily v isible a ngular v oid. A ll o f t he s pecimens w ere b roken t o e xpose c ross-sections t hat h ad n ot b een s ubjected t o s oil a brasion o r p ost-excavation m odification. T hese w ere m ounted o n a luminum s tubs a nd c oated w ith a pproximately 2 00 A ngstroms

o f

g old

a n E TEC O mniscan e lectron m ode.

i n a s putter c oater. s canning

e lectron

T hey w ere

m icroscope

t hen e xamined u sing

( SEM)

i n

t he

s econdary

A nother 1 2 P omona s herds, a ll f rom s ite 1 4MM213, w ere p repared a s t hin s ections t o d etermine t he n ature o f t he l inings s een o n t he w alls o f s ome v oids. T hese t hin-sections w ere c ompared t o t hin s ections o f soil f eatures i llustrated i n s tandard m anuals ( Brewer, 1 964; F itzpatrick, 1 984). T he p reparation o f t hin s ections o f p otsherds w ithout t he l oss o f o riginal f abric, e specially v oid s paces, i s d ifficult a nd i s u nfamiliar t o m ost a rchaeologists. F or t his r eason,

8 7

t he p rocess u sed i s d escribed h ere i n d etail. B ecause

l ow-fired

s herds

a re q uite

s oft,

t hey m ust b e i mpregnated

w ith e poxy p rior t o g rinding. P etropoxy 1 54 r esin a nd c uring a gent w ere u sed. T he f ollowing r ecipe a llows f or t he p reparation o f a bout s ix s herds t hat a re 2 5 m m i n d iameter a nd r oughly 7 m m t hick. Amounts c an b e i ncreased p roportionately f or l arger n umbers o f s pecimens. P rocessing l arge b atches o f s pecimens r educes t he p reparation t ime p er s pecimen. T en m l o f P etropoxy 1 54 i s f irst h eated t o 1 00"C . T hen 1 00 m g o f P etropoxy 1 54 b lue d ye i s a dded. T he p urpose o f t he d ye i s t o a llow t he i nvestigator t o d istinguish b etween t he o riginal v oids i n t he s pecimen a nd a ny t hat m ight b e c reated d uring c utting a nd g rinding. T he r esin-dye m ixture i s t hen h eated i n a n o ven a t 1 30 C f or t wo h ours, w ith f requent s tirring. T he h eating a nd s tirring s hould c ontinue u ntil t he p owdered d ye i s c ompletely d issolved i n t he r esin. O nce t he m ixing i s c omplete, o ne m l o f P etropoxy 1 54 c uring a gent i s a dded, u sing a s yringe, a nd t he r esin i s s tirred f or 3 0 s econds. A s mall a mount ( 2-3 m l) o f i sopropyl a lcohol c an b e a dded t o t he m ixture t o d ecrease i ts v iscosity. T his w ill r educe p roblems w ith a ir b ubbles a nd w ill i ncrease t he d egree o f p enetration o f t he s pecimens. T o s aturate t he s pecimens w ith t he e poxy, a v acuum i mpregnator c apable o f d rawing 5 00 m m o f m ercury i s u sed. E ach s herd i s i mmersed i n t he r esin ( 20 m l p lastic c ups a re h andy f or t his) a nd p laced i n t he v acuum c hamber. O nce t he v acuum r eaches t he maximum l imit ( 550 mm o f m ercury i n t his c ase), t he p ump i s t urned o ff a nd t he s pecimens a re l eft i n t he s ealed c hamber f or f ive m inutes. A ir b ubbles w ill f orm a t t he s urface o f t he r esin. A fter t he f ive m inutes h ave p assed, t he c hamber i s o pened a nd t he l iquid s tirred g ently t o r emove t he b ubbles. T his p rocedure i s r epeated u ntil a ir b ubbles n o l onger f orm . T he s herds a re t hen p laced i n a n o ven f or o ne h our a t 1 30"C.

T his

h eat t reatment h ardens t he e poxy. L arger s herds, e specially t hick o nes, m ay r equire l onger h eating t imes. D epending o n t he p orosity o f t he s herds, s ome e xperimentation m ay b e n ecessary t o a chieve c omplete i mpregnation o f t he s herds. I ncomplete d osing m ay l ead t o t he f ormation o f a ir b ubbles w hen t he s herds a re a ttached t o t he m icroscope s lides, l eading t o p roblems d uring t he g rinding o f t he t hin s ections. U pon c ooling,

t he s herds a re g round f lat a long o ne e dge w ith a 6 00

g rit g rinding w heel. A t t his p oint i t w ill b e o bvious w hether t he s herd i nterior h as b een c ompletely i mpregnated. I f n ot, e poxy c an b e a pplied t o t he g round s urface a nd c hamber t o c omplete t he p rocess.

t he

s herd

r eturned

t o

t he

v acuum

I t i s u seful t o e xamine t he e dge o f t he g round s herd u nder a b inocular m icroscope e ven b efore m ore e poxy i s a dded. C areful s canning o f t he g round s urfaces d uring t his s tudy r evealed d etails o f t he f abric t hat m ight h ave b een m issed h ad m ore e poxy b een a dded a nd t he e dge r eg round. O nce a ny n eeded e poxy h as b een a dded a nd t he e dge r efinished, m icroscopic e xamination a lternating w ith g rinding w ill a llow t he i nvestigator t o c hoose f eatures o f i nterest.

a

c ross-section

8 8

t hat

c learly

r eveals

t he

s herd

O nce a s urface w ith f eatures o f i nterest h as b een e xposed, t he i s m ounted o n a p etrographic g lass s lide u sing t he s ame t en-to-

o ne m ixture o f r esin t o c uring a gent, b ut w ithout t he d ye. J ust e nough e poxy t o c over t he g round s urface s hould b e a pplied t o t he s herd p rior t o

p lacing

i ts

g round

e dge

d own

o n

t he

s lide.

( Too

m uch

e poxy c an

c rack t he s lide.) N ext, t he s lide a nd s pecimen a re h eated t o 1 00 - C o n a h otplate, a nd t he j unction b etween t hem i nspected f or a ir b ubbles. I t i s c ritical t hat s uch b ubbles b e r emoved b ecause t hey p revent g rinding o f t he s pecimen t o t he a ppropriate t hickness. R emoval i s a ccomplished b y a pplying p ressure o n t he s herd a nd b y s liding i t s lightly a cross t he s lide. W hen t he a ir b ubbles h ave b een r emoved, t he s eal b etween s pecimen a nd s lide i s h ardened b y p lacing t hem i n t he o ven a t 1 30 - C f or t hree h ours. A b utterfly s tyle p aper c lip c an b e u sed a s a v ise t o h elp e nsure a g ood b onding. T he s lides a re t hen r emoved a nd a llowed t o c ool. F ollowing t his, t he s herd i s c ut w ith a s aw o r g round o n a w heel t o a t hickness o f a pproximately 1 00 m icrons. T he s pecimen i s t hen g round t o t he s tandard 3 0 m icron t hickness f or t hin s ection a nalysis w ith 6 00 f aceting g rit o n a g lass p late. T he t hickness o f t he s ection i s c hecked u sing a p etrographic m icroscope w ith a s tandard c olor c hart.

R esults E xamination 2 a) s howed t he s eparated f rom

o f t he u ndisturbed p resence o f o ne a nother

s ubsoil

s ample w ith

t he

w ell-defined b locky p eds. b y c revice-like v oids, a nd

S EM

( Fig.

S ome m ost

w ere w ere

p enetrated b y s mall c ircular t o o val v oids 2 2 t o 1 34 m icrons i n maximum d imension.

t he

B oth t he s herd i dentified o ptically a s o ne i dentified a s h aving g rog t emper

h aving a b locky p aste a nd ( Fig. 2 b) w ere b asically

i dentical t o t he s ubsoil. I ndeed, c lose e xamination o f t he l atter l ed t o r eclassifying i t a s u ntempered, w ith a p oorly m ixed s ubsoil p aste. T he c revice-like b reaks b etween p eds w ere v isible i n b oth s herd s pecimens. S maller v oids i n a v ariety o f s hapes a nd s izes w ere a lso r ecorded. S ome w ere r ound t o o val, w hile o thers w ere i rregular i n o utline. T hese s pecimens w ere a lso c ompared t o t he d aub s amples a nd t he i ntentionally t empered s herd. T he d aub ( Fig. 3 a) i s d istinct i n a ppearance f rom a ll o f t he p ottery, e ven a t l ow p ower. I t l acks a ny s uggestion o f t he p resence o f p eds o r c oncretions. O nly a f ew s mall v oids a re p resent. I t i s g ranular i n a ppearance, a pparently a s a r esult o f t he p resence o f n umerous l oess g rains t ypically f ound i n n ear-surface z ones o f t he u pland s oils o f t he r egion. T he g ranite-tempered s herd ( Fig. 3 b) h as a p aste t hat i s s imilar i n g eneral t exture t o t he r est o f t he p ottery. I t l acks, h owever, a ny s ign o f p ed s tructure, c oncretions, o r f lat v oids.

T he t emper t ends t o

b e l arge i n c omparison t o t he i nclusions s een i n t he P omona s herds, t he p aste i s f ree o f a ll b ut l oess-sized i nclusions.

4 a).

a nd

M ost o f t he P omona s herds e xhibited a v ariety o f f eatures ( Fig. A s ingle b roken e dge m ight h ave c oncretions, p eds, f lat s mooth

a

Fig. 2 . a . U ndisturbed s ubsoil p eds, voids. S cale b ar = 1 000 m icrons. b . S cale bar = 5 00 microns.

9 0

s howing i nter- a nd i ntra-ped P eds preserved i n a P omona s herd .

a

F ig.

3 .

s ubsoil

a .

D aub

s ample,

f eatures.

s howing

S cale bar

a l ack o f

= 5 00

A q uartz c rystal i s a t b ottom S cale b ar = 2 00 m icrons.

m icrons.

c enter

9 1

i n

l arge b .

f ront

v oids a nd o ther l arge

G ranite-tempered o f

a f eldspar

s herd.

c rystal.

v oids, f lat i rregular v oids, s mooth r ounded v oids, a nd s mooth a ngular v oids. S ome v oids w ere l ined, w hile o thers w ere u nlined. C lose e xamination o f t hese u nder a v ariety o f m agnifications c larified t he o rigins o f s ome o f t he f eatures. A t c reated

l east o ne a ngular b y a s olid o bject

v oid w ith s mooth e dges ( Fig. 4 a:1) i n t he p aste a t t he t ime t he v essel

f ormed. T he o bject w as l ater r emoved, f iring o r b y l eaching a fter d eposition.

w as w as

e ither b y c ombustion d uring T hat t he v oid w as f illed a t

t he t ime t he v essel w as s haped i s e vident f rom t he d istortion o f a n a djacent f lat, i rregular v oid a round t he a ngular v oid ( Fig. 4 a:2). T he w alls o f t he v oid a re f lat a nd f eatureless, e ven u nder h igh m agnification, r endering i dentification o f t he p article i t c ontained a n i mpossible t ask. F lat, i rregular v oids ( Fig. 4 a:2, F ig. 4 b) m ay h ave b een f ormed b y t wo p rocesses. S ome a re s paces i n t he o riginal s ubsoil t hat w ere f lattened d uring t he s haping o f t he v essel w ith a p addle a nd a nvil. O thers m ay h ave b een c reated b y t he s trains r esulting f rom t he s haping p rocess. T hese v oids t end t o l ie p arallel t o t he s urfaces o f t he s herds, e xcept w here t hey a re a djacent t o s olid o bjects i n t he p aste. A t l ow m agnifications, t hey ( Fig. 4 a:4) a re r eadily m istaken f or t he f lat,

s mooth-walled c ells a pparently l eft b y l eached s hell t emper

( Fig.

4 a:3). A t h igher m agnifications w ith t he S EM, h owever, i t i s p ossible t o l ook d own i nto t he v oids a nd d istinguish t hese t ypes b y t he s moothness o f t heir w alls. T he v oids p resumably l eft b y l eached s hell t emper ( Fig. 5 a:2) h ave s mooth, f eatureless s ides, e ven a t v ery h igh m agnifications. T he f lat i rregular v oids, i n c ontrast, h ave s ides w hich r etain t he i rregularities o f t he o riginal s ubsoil v oids ( Fig. 4 b). S ome o ther f airly s mooth-walled v oids a ppear t o h ave b een c reated b y o rganic o bjects ( Fig. 4 a:5). T hey t end t o h ave r ounded e dges a nd a re c ircular t o e lliptical i n o utline. S ome a re l ikely t o b e m olds o f f ine r ootlets. A f ew ( Fig. 5 b) r etain w hat a ppear t o b e o pal p hytolith s tructures. A c opy o f F igure 5 w as e xamined b y P . T wiss ( pers. c omm .), w ho w as a ble t o i dentify t he s tructure i n t he v oid a s ap robable o pal p hytolith, b ut, b ecause o f t he d istortion p resumably c aused b y f iring o f t he v essel, c ould n ot d etermine m onocotyledon o r a d icotyledon. S till o ther v oids s ubstance t hat t ends t o p etrographic m icroscope l inings, w hich h ave l ow

w hether

i t

w as

d erived

f rom

a

( Fig. 4 a:6, F ig. 5 a:1) a re l ined w ith a d ense c harge u nder t he S EM b eam . E xamination u nder a i n t hin s ection i ndicates t hat t hese a re c lay c onductivity a nd h ence c harge r eadily. G iven

t hat t he s herds a re l ow-fired, i t i s c onceivable t hat s ome l inings w ere c reated a fter d eposition b y s oil f ormation p rocesses. O ther v oids.

T he

s herds l ining

( Figs. i n

4 a

a nd

5 a)

c ontain

b oth

l ined

a nd

u nlined

t hese c ases a ppears t o d iffer i n n ature f rom t he

a bove e xamples. T his m akes a p ost-depositional o rigin f or t hese l inings u nlikely. I t i s d ifficult t o c onceive o f s oil c onditions s uch t hat o ne v oid w ould b ecome l ined w hile a nother o f s imilar s hape a nd s ize o nly a m illimeter a way w ould n ot. I t i s m ore l ikely t hat t he v oids

h ave

b ecome

l ined p rior t o c ollecting

9 2

o f

t he

c lay

f rom t he

a

F ig.

4 .

a ngular v oids ( 7).

a .

( 5), S cale

( 1600X).

T ypical P omona s herd e xhibiting s ubsoil f eatures:

v oid

( 1),

i rregular

c utan-lined v oid bar

- 1 000

v oids ( 6),

m icrons.

( 2,

4 ),

s mooth

f lat

v oid

l arge ( 3),

o val

a nd f errous-manganese oxide c oncretion b .

I rregular v oid a t h igh magnification

S mall v esicles i n c lay matrix a re v isible a bove t he v oid.

S cale bar - 1 0 m icrons.

9 3

a

b

F ig.

5 .

a .

C utan-lined v oids

c utan h as b roken o rganic material.

( 1)

a nd s mooth v oid

( 2)

f rom w hich t he

a way. S cale b ar = 5 00 m icrons. b . V oid p roduced b y R emnants o f t he o rganic s tructure a re v isible i n t he

r ight-hand s ide o f t he v oid.

S cale b ar = 5 0 m icrons.

9 4

s ubsoil b y t he p otter. T he r eason f or t his b ecame s herds w ere e xamined i n t hin s ection ( see b elow).

c lear

w hen

t he

C oncretions, w hen v iewed i n c ross-section ( Fig. 4 a:7) a re s hown t o h ave a t exture v ery s imilar t o t hat o f t he s urrounding p aste. T his i s n ot s urprising, s ince t hey a re c omposed o f s ubsoil c lay p articles t hat h ave b ecome c emented w ith i ron a nd m anganese o xides. A ll b ut t he s mallest c oncretions a re r eadily s een w ith t he n aked e ye o r a l ow-power h and

l ens.

R eddish

t o b lack

i n

a re s hiny w hen f reshly e xposed.

c olor,

t heir o uter

s urfaces s ometimes

O n e roded s herd s urfaces,

h owever,

t he

c oncretions m imic g rog t emper, a nd e ven t heir r ounded s hape c annot d istinguish t hem f rom p ieces o f c rushed p ottery, t he o utlines o f w hich a re r ounded b y e rosion. I n t hin s ection, t he c oncretions t end t o b e m arked w ith c oncentric r eddish-brown i ron o xide s tains. A f ortuitous

d iscovery m ade w hile

m agnification ( 1600X) w as e vidence t hat t he p oint t hat t hey h ad b egun t o b loat w ere v isible o n b roken p aste s urfaces.

e xamining

t he v oids

u nder h igh

s ome s herds h ad b een h eated t o ( Fig. 4 b). S mall g as b ubbles T hese m ay b e d erived f rom t he

c ombustion o f m inute o rganic p articles w hich w ould h ave b een r emoved i f t he c lay h ad b een a ged p roperly. I f t he v essels h ad b een f ired a t h igher t emperatures, t he b loating w ould h ave w eakened t he v essel w alls t o t he p oint t hat t hey w ould h ave b egun t o f low, d istorting t he v essel s hape. T he s pecimens t hat w ere t hin-sectioned w ere e xamined w ith a b inocular m icroscope a fter o ne f ace h ad b een g round f lat. S ome s howed a v ariety o f t ypes o f c oncretions a nd v oids. A f ew o f t he v oids w ere s urrounded w ith d ark g ray paste t hat w as f ired i n a r educed s tate b ecause c ombustion o f o rganic m aterial i n t he v oid u sed u p t he a vailable oxygen. R educed c lay a round s ome v oids w as v isible o n o ne s pecimen p rior t o c oating w ith g old f or S EM e xamination. f eatures, h owever, w ere i nvisible i n t he S EM, s ince t hey i nvolve a ny a lteration o f t he t opography o f t he b roken e dge. O ne m istaken

s pecimen f or g rog

T hese d id n ot

( Fig. 6 a) c ontained f eatures t hat m ight r eadily b e t emper. T he p aste o f t he s herd i s n early f ree o f

s and, b ut a s tructure w ithin t he s herd c ontains a bundant f ine s and a nd a c oncretion ( that a lso c ontains s and). T he s tructure i s p robably a v ermiform, i .e. a f illed w orm c hannel, c ontaining m aterial t ranslocated f rom a nother s oil h orizon ( cf. F itzpatrick, 1 984: F ig. 7 .22). I n a nother s pecimen ( Fig. 6 b), s everal r egular v oids c ontained a w hite m ineral. D ilute h ydrochloric a cid w as a pplied t o d etermine w hether t he m aterial w as e ffervescent. S ince i t w as n ot, i t c annot b e m ussel s hell t emper. A dditional w ork w ill b e n eeded t o d etermine i ts c omposition. i n t he c enter w ith a c utan. t he p hotograph

T he s ame s pecimen c ontained v oids, s uch a s t he l arge o ne o f t he p hotograph ( Fig. 6 b), w hich w ere c learly l ined T he s maller, f lat v oids h ave s imilar l inings, v isible i n a s d ark g ray r ims.

E xamination o f t he s herds i n t hin s ection w ith a p etrographic m icroscope h elped t o c larify s ome o f t he f eatures i n t he p aste. I dentification o f t emper a nd i nclusion m inerals i s s traightforward w ith t he p etrographic m icroscope. F igure 7 s hows a s herd t hat i s t empered w ith f ine q uartz s and a nd t hat h as s mooth, f lat v oids a s i nclusions.

9 5

F ig. 6 . a . O ptical m icroscopic v iew o f t he c ross-section o f a s herd t hat c ontains a v ermiform, t he c ontents o f w hich c ontain f ine s and. T he r ounded e dge o f t he v ermiform d istinguishes i t f rom Z g rog. S cale b ar = 3 mm . b . O ptical m icroscopic v iew o f t he c ross-section o f a s herd w ith a v ariety o f v oids l ined w ith c utans. T he l ining o f t he l arge v oid i n t he c enter i s r eadily v isible b y c olor d ifferences b etween i t a nd t he s urrounding p aste. S cale b ar = 3 mm .

9 6

F ig.

7 .

T hin-section

v iew

o f

a s and-tempered

s herd

t hat

c ontains

s mooth f lat v oids a s i nclusions. A t hin, d ark l ining o f o rganic m aterial c oats t hese v oids. T he l ining i s m ost a pparent a long t he t op o f t he l owest v oid i n t he p hotograph. S cale b ar = 2 m m.

9 7

T he s mooth f lat v oids i n t his s herd h ave a t hin, d ark l ining, a pparently m ade u p o f a n o rganic m aterial. I rregular v oids i n t he s ame s herd d o n ot e xhibit t his l ining. S ince t he i rregular v oids a re e ither i nter-ped v oids o r p roducts o f t he p rocess o f m anufacture, t his i s a c lue a s t o t he s ource o f t he l ining m aterial. W hen b oth u nlined a nd l ined v oids a re i nterspersed i n a s ingle s herd, t hey h ave b oth b een e xposed t o t he s ame e nvironment o f d eposition. I n t his c ase, i t i s s afe t o c onclude t hat t he m aterial f orming t he l ining o f s ome o f t he v oids m ust b e d erived f rom t he p articles t hat f ormed t he v oids. T hus, t he o rganic l ining s een i n t he r egular v oids i n F igure f rom a n o rganic m aterial t hat o nce f illed t hem .

7 m ust

d erive

T he p rocess o f f orming t he v essels w as a lso c lear i n t hin s ection. T he c lay particles i n t he P omona s herds w ere m oderately t o h ighly a ligned w ith t he s urfaces o f t he s herds. T he o rientation o f c lay p articles c an b e o bserved w hen t he t hin s ections a re o bserved u sing c rossed p olarizers. I f a q uartz p late i s a dded, t he o rientation i s a pparent i n c olor c hanges t hat o ccur w hen t he m icroscope s tage i s r otated. T he m oderate t o h igh o rientation o f t he c lay a pparently i s t he r esult o f u se o f t he paddle a nd a nvil m ethod o f s haping t he p ots ( J. G undersen, p ers. c omm). S uch s trong a lignment i s n ot a pparent i n a s eries o f M iddle W oodland p eriod v essels a vailable.

f or w hich

t hin

s ections w ere

O ne s herd t hat c ontained h ighly a ligned c lay p articles a lso c ontained a p ed. S ince t he p ed d id n ot d issolve d uring t he m ixing o f t he p aste, t he c lay p articles i n i t d id n ot h ave a c hance t o b ecome a ligned d uring m anufacture o f t he v essel. W hen t he m icroscope s tage w as r otated, t he p ed r emained t he s ame c olor, w hile t he s urrounding paste c hanged c olors. T his p rovides a n a dditional m eans o f d istinguishing p eds ( which w ill n ot h ave a ligned c lay p latelets) f rom g rog t emper ( which w ill r etain i ts o riginal o rientation, e ven t hough t his s hould b e d ifferent f rom t hat o f t he s urrounding p aste).

C onclusions E xamination o f

P omona s herds w ith t he S EM p rovides s trong s upport

f or t he h ypothesis t hat t hey w ere m ade f rom s ubsoil c lays. T he b ulk o f P omona c eramics a ppear t o b e u ntempered. T he n umerous i nclusions i n t hem a re a lso p resent i n t he c lay-rich s ubsoils o f t he O sage C uestas p hysiographic p rovince. B ecause t he c lays w ere n ot g round o r w ere o nly p oorly g round p rior t o u se, s ubsoil p eds, c oncretions a nd v oids w ere f requently p reserved i n t he p ottery. V essels m ade f rom c lay t hat w as m ixed o nly m inimally a re o ften i dentified a s h aving g rog t emper. S herds t hat c ontain a l arge n umber o f f errous-manganese c oncretions a re l ikewise o ften m isidentified. S ome v oids c ompressed d uring m anufacture a re s imilar i n a ppearance t o v oids l eft b y l eached s hell t emper. S ome v oids a ppear t o h ave b een p resent i n t he s ubsoil; o thers may b e p roduced d uring t he m anufacturing p rocess. A rgillic c utans i n s ome v oids mimic s hale p articles. A nalysis o f P omona c eramics h as b een c omplicated b y t he c onfusion o f t hese i nclusions w ith t he g rog, s hell a nd o ther t rue t empers t hat a re o ccasionally f ound i n s herds f rom s ome P omona s ites.

9 8

B ecause

t he

s ubsoil

c lays

w ere

t he paste i s r ich i n o rganics. a reas

o f

v oids. t he

c lay

s urrounding

v oids

l eaving r educed

o r o rganic l inings o n t he w alls o f t he

M ore g enerally d istributed m inute o rganic particles i mbedded i n

c lay

c aused

t emperatures. t han

n ot a ged prior t o u se i n c eramics,

L arge particles b urned,

b oth

t he

c lays

t o

P omona pottery,

e arlier

a nd

l ater

b loat

i f

t hey

w ere

f ired

a t

h igh

t hus f ired a t l ow t emperatures i s s ofter

c eramics f rom t he s ame r egion t hat c ontain

t rue t empers. P omona

c eramics

may

b e

s een

a s

a n

a daptation

t o

a particular

e nvironment. T he c lay r ich s ubsoils o f t he O sage C uestas province c ontain n umerous i nsoluble t o partly s oluble particles t hat precluded t he

n ecessity

o f

t empering

t he

c lay.

I ndeed,

i n o rder

t o

r etain

t he

particles, processing t he c lay p rior t o u se w as n ot o nly u nnecessary, b ut h ad t o be a bandoned. T his, i n t urn, mandated a l ow f iring t emperature. t ypes,

T he

n umerous,

e specially

r esult,

o n

t he

a rchaeologists

v aried

e roded

i nclusions

s urfaces

a ccustomed

t o

o f

m imic

various

l ow-fired

l ooking

f or

t emper

s herds.

A s

a

t emper h ave b een

l ed

c an b e m istaken

f or

a stray.

Future Work While t hose w ith

t his

l eft by s hell

s tudy

h as

l eached

t emper

s hown

s hell

must

b e

t hat

t emper, d one

s o

o ther voids

more

work

i s

n eeded.

t hat

t he v oids

E xperiments

c reated w hen

s hell

t emper i s l eached f rom pottery c an b e c haracterized p recisely e nough t o d etermine t his t he

which

way. O sage

t he

C uestas

e xamination

o f

c omposition mapping

o f

S tudies

o f

t he a n

voids

s amples

a re

t hese

w ould b e

f lat

o f

a lso

s ubsoils f eatures

i n

P omona pottery w ere produced

f rom t he

a rgillic

n ecessary. a re

n eeded

s een

a ppropriate

i n

B oth t o

h orizons

s oils

t hin-section

d ocument

P omona

o f

i n o f

a nd

S EM

t he p resence

a nd

p ottery.

S EM

a nd

X -ray

s trategy f or i dentifying i nclusions

i n

b oth t he s ubsoils a nd t he pottery.

Acknowledgements D r.

P age

i dentified James w ith

T wiss

t he

G undersen t he

. (Kansas

s tructure ( Wichita

t hin-section

i n

S tate t he

S tate

a nalysis

U niversity) void

a s

U niversity) a nd

e xamined F igure

a possible

5 b a nd

phytolith.

D r.

k indly provided a ssistance

i dentification

o f

various

f eatures

s een i n t he t hin s ections.

References B ell, E .H. a nd G ilmore, G .H. 1 936. T he N ehawka a nd T able R ock F oci o f t he N ebraska A spect. I n E .H. B ell, C hapters i n N ebraska Archaeology, pp.

3 01-356.

B lakeslee,

U niversity o f N ebraska, D .J.

a nd

R ohn,

A .H.

L incoln, 1 986.

N ortheastern K ansas: T he H illsdale E ngineers, K ansas C ity D istrict.

9 9

Lake

N ebraska. Man

P roject.

a nd U .S.

E nvironment Army

C orps

i n o f

B rewer,

R .

a nd S ons, B rown, a nd

1 964.

F abric

o f

S oils.

J ohn W iley

N ew Y ork.

K .L.

1 984.

Western

P omona:

M issouri.

Anthropology,

F itzpatrick, L ondon. A .H.

L ake,

K ansas.

P hysiography

1 984.

a nd D aniel,

d issertation,

o f

t he

Western

M icromorphology o f S oils.

K .J.

W ichita

2 , W ichita,

S hepard, A .O.

P h.D.

D epartment o f

U niversity o f K ansas.

E .A .

R ohn,

a P lains V illage variant i n E astern K ansas

U npublished

F enneman, N .M. 1 931. M cGraw-Hill, N ew York.

N o.

a nd M ineral Analysis

S tate

1 984.

U nited

C hapman a nd H all,

R ocky Ford Archaeology,

U niversity

S tates.

Publications

H illsdale

i n Anthropology,

Kansas. 1 954.

C eramics f or t he a rchaeologist.

Publication 6 09,

C arnegie I nstitution o f Washington. S oil

C onservation

S oil

C lassification

S ervice. f or

1 975.

Making

D epartment o f A griculture Handbook, S oil

C onservation

S ervice.

S oil

a nd

Taxonomy:

I nterpreting N o.

1 979.

4 36,

S oil

S urvey

o f

U .S.

D epartment o f Agriculture, Washington,

W ilmeth,

R .

1 970.

T .

1 967.

N ewsletter 1 2 Witty,

T .

( 9):

1 981.

Archaeologist 4 2:

T he P omona f ocus.

U .S.

J ohnson

No.

5 ,

C ounty,

D .C.

Excavations i n t he P omona R eservoir.

H istorical S ociety, Anthropological S eries,

S ystem o f

S urveys.

Washington, D .C .

K ansas.

Witty,

a B asic

S oil

T opeka,

Kansas S tate Kansas.

K ansas Anthropological A ssociation

1 -5. T he

P omona

f ocus,

7 7-84.

1 00

k nown

a nd u nknown.

The M issouri

P ART I V :

STONE ART IFACTS AND M INERALOGY

1 01

Q UARTZ G RAINS S TUDIES: E NVIRONMENTAL R ECONSTRUCTION F OR ARCHAEOLOGISTS B Y S CANNING E LECTRON M ICROSCOPY P .A . B ull a nd A .M . M agee

S ummary S canning e lectron m icroscope f rom

a rchaeological

s ites

c an

( SEM)

t hrow

a nalysis o f q uartz g rains t aken

m uch

l ight

u pon

t he

p roblematic

g eologic l ayers b arren o f a rtefacts a nd o ther k inds o f s edimentary e vidence. S EM a nalysis c an i dentify p alaeoenvironmental h istories o f t he m aterial a nd i ndicate t heir p rovenance a nd p alaeoenergy c onditions o f e mplacement. A c ase s tudy o f T abun C ave, M ount C armel, I srael i s p rovided a s a n e xample o f S EM r econstruction t echniques.

I ntroduction I n

r ecent

y ears

a rchaeologists

h ave b egun

t o

t ake v ery t entative

s teps t owards q uartz g rains s tudies b y S EM i n o rder t o r econstruct p ast e nvironments S weitzer, c ave

i n

1 975;

s equences

e ssentially

a rchaeological

s ites

a nd M eie e t a l., s uch

a s

g eologic

t hose o f s ites

( e.g.

1 981). t he

w hich

T ankard,

1 974;

T ankard a nd

T hese s ites r ange f rom c lassic

P eking M an c ontain

s ite

( Zhoukoudian)

m inimal

t o

a rchaeological

m aterial. T he p roblems w hich e xists f or t hese a rchaeologically-trained S EM " beginners" i s, o n t he f ace o f i t, q uite d aunting. T here a re o ver s even h undred published p apers o n t he u se o f t he S EM a s a t ool i n e nvironmental d iscrimination ( see B ull, 1 981; K rinsley a nd T rusty, 1 986; B ull e t a l., 1 987). W ith s ome o f t he papers, a t l east, t here i s t estimony t o i nadequate t raining a nd g rasp o f S EM r ationale. T hese p ublished " red h errings" s erve t o c onfuse r ather t han h elp r eaders. A s a r esult o f t his l iterary m ine-field, t his paper i ntends t o s et o ut a s s imply a s p ossible s ome d o's a nd d on'ts o f s ample c ollection, p reparation a nalysis a nd i nterpretation p rocedures w ith p articular r eference t o a rchaeological p roblems. I t

i s

p erhaps

t o t he

a dvantage o f a rchaeologists t hat m any o f t he

p roblems i n S EM i nterpretation o f q uartz g rains h ave a lready b een s orted o ut. F rom t he e arly d ays i n t he 1 960's w hen i t w as p ossible t o e xamine b ut a f ew g rains, p hotograph t hem i n t he S EM a nd t hen p ublish t he r esults, w e h ave n ow m oved i nto a m ore s cientific m ethod o f e nquiry. S o l ong a s t he r ecord i s p reserved o n t he s urface o f t he g rains t o b e e xamined, i t i s n ow p ossible t o r econstruct i n g reat d etail t he p alaeoenvironmental h istory o f a s ample. T his i s o f p articular i nterest t o a rchaeologists w ho, w hen e xamining s edimentary l ayers, o ften d esignate t hem " barren" o f a rchaeological a rtefacts. I f t hese l ayers c ontain q uartz s and g rains, i t i s p robable t hat t hey a re o f m ore v alue i n e nvironmental r econstruction t han t he a rtefacts t hemselves. I t i s i mportant t o r emember t hat w e c an o ften t ell m ore f rom t he b its o f s ediment w hich a rchaeologists t hrow a way t han t hey c an f rom a rtefacts w hich t hey k eep a nd s tudy i ntently. I t i s n ot j ust a c ase o f t hrowing t he b aby o ut w ith t he b ath w ater; i t i s r ather t hat t he

b ath

w ater

c onjunction

w ith

w as

n ever

o ther

c ollected

m ore

i n

s tandard

1 03

t he

f irst

p lace.

a rchaeological

U sed

i n

i nvestigation

t echniques, t he S EM c an p rovide r econstruction o f p rehistory.

a m ost

p owerful

a djunct

t o

t he

T he b asic r ationale o f t he t echnique i s q uite s traight f orward. Q uartz g rains, w hich h ave b een w eathered a nd e roded f rom t heir p arent r ock, a re o ften t ransported o n t heir j ourney u ltimately t o t he s ea b y a n umber o f d ifferent m odes o f t ransportation. S uch m odes i nclude t ransportation b y g laciers, r ivers, a nd w ind. E ach o f t hese d ifferent m odes o f t ransportation m ove g rains i n a d ifferent m anner. G laciers, f or e xample, m ove m aterial b y g rinding a nd c rushing; h ence t he g rains t end t o e xhibit v ery s harp e dges a nd h igh r elief ( Fig. 1 ). A ssociated w ith t his g rinding a ction, g rains o ften e xhibit s urfaces w hich a ppear t o h ave b een s cratched a nd c rushed, a nd g enerally s how m uch d isruption. Q uartz g rains w hich h ave b een t ransported b y f luvial a ction, o r i ndeed b y s ub-aqueous a ction s uch a s m ovement i n t he s ea, s how s urfaces w hich h ave b een g enerally r ounded; e dges a re v ery o ften a braded a nd t he g rain s urface o ften e xhibits u biquitous d isoriented V -pit s tructures ( Fig. 2 ). T hose g rains m oved b y a eolian t ransportation s how b roadly s imilar f eatures o f r educed r elief a nd d ulled e dges. T his i s, o f c ourse, b ecause t he m echanism o f t ransportation b y r olling a nd b ouncing t he g rains i s r oughly t he s ame a s t hat o f s ub-aqueous t ransportation, a lthough t he m edium o f t ransport i s d ifferent. T he m ost c haracteristic f eatures f ound o n t he s urfaces o f q uartz g rains w hich h ave b een m odified b y a eolian a ction a re: d ish-shaped c oncavities ( Fig. 3 ) a nd c rescentic i mpact p its. I t i s p erhaps i mportant t o n ote h ere t hat w hilst p articular t ypes o f s ediment t ransport c an i mpart f eatures o n t he s urface o f q uartz g rains t hat a ppear u nique t o t hat e nvironment, w e a re i n f act d ealing w ith " sets" o f e nergy c onditions w hich t hemselves m ay

b e

c haracteristic

o f

t hat

e nvironment.

T his

i s

n ot

a p edantic

point s ince e nergy c onditions n eed n ot a lways b e u nique t o o ne p articular t ype o f t ransportation. I t i s c rucial t herefore t o s eek o ther l ines o f c orroborative e vidence s uch a s s edimentary s tructures a nd g rain-size d istributions a nd n ot i ndicator o f a ny particular e nvironment. O ne

o f

t he

g reat

a dvantages

o f

u se

t he

S EM

a s

i nvestigating

a

q uartz

o ne

s tep

s urface

t extures i s t hat q uartz i s a v ery r esistant m ineral. I t c an o ften p ass t hrough a l arge n umber o f d ifferent e nvironments, e ven d uring o ne s edimentary c ycle. I t i s p ossible t herefore, t o e nvisage a s ituation w here i t m ay b e possible f rom t he c ombination o f t he t extures o n t he s urface o f

g rains,

t o

i dentify a c omplex p alaeo-history f or t he g rain.

A g rain m ay s tart i ts l ife i n a M illstone G rit o utcrop, b e w eathered a nd e roded b y a g lacier d ownstream a nd w hen t he g lacier m elts, b e d eposited i n a s oil s equence, w here i t i s l ater e roded b y a r iver, t ransported t o t he s ea, a nd u ltimately t hrown u p o nto a d une r idge o r s torm b each. T his r idge m ay t hen b e s ubmerged a nd l ater i nvestigated v ia a b orehole s unk o n t he s hore. S EM t echniques c an b e u sed t o r econstruct t his h istory ( Bull l nd C ulver, 1 980). I t

i s

a lso

e qually

p ossible

t o

r econstruct

t he

e nvironmental

h istory o f a s and g rain t hrough a n umber o f d ifferent s edimentary c ycles. Q uartz g rains l aid d own i n a d eposit t hat i s u ltimately l ithified t o a s andstone, w ill c ontain s urface f eatures w hich a re r epresentative o f t he t ransportation m echanisms p rior t o l ithification o f t hat r ock. W hilst, o f c ourse, t his c an c onfuse p resent d ay a nalysts w ho

i nvestigate

t he q uartz

g rains

t hat h ave n ow b een r emoved f rom t hat

1 04

F ig. i n

1 .

S EM photomicrograph o f q uartz g rain t aken f rom a g lacial s nout

Kashmir,

f ractures,

F ig.

2 .

S wansea,

I ndia.

N ote

t he

s harp

s mall a dhering particles,

S EM photomicrograph Wales.

N ote

g enerally w ell-rounded,

t he

e dges,

h igh

r elief,

c onchoidal

a rc-shaped s teps a nd s cratches.

o f a q uartz g rain t aken f rom C aswell B ay, ubiquitous

l ow r elief g rain.

1 05

n on-oriented

V -pits

C ompare w ith F igure

upon 1 .

a

F ig.

3 .

S EM p hotomicrograph o f

d esert. T he g rain i s d ish-shaped c oncavities.

a q uartz g rain

w ell-rounded,

1 06

e xhibits

f rom t he S audi A rabian l ow

r elief

a nd

g entle

r ock b y w eathering p rocesses, g eologists c an u se t he p alimpsest o f s urface t extures t o i ndicate f rom w hich r ock b ody t his p articular m aterial h as b een d erived ( Scholle a nd H oyt, 1 973; C och, 1 975). N ot o nly, t herefore, c an p alaeoenvironmental h istories b e r econstructed f rom t he s and g rain s urfaces, b ut i n c ertain i nstances w e c an a lso i dentify provenance. Examples of b oth p alaeoenvironmental r econstruction a nd p rovenance s tudies a re d etailed l ater i n t his p aper.

S ample C ollection a nd P reparation T he m ost p owerful u sage o f t he S EM t echnique i n e nvironmental d iscrimination f or a rchaeologists, i s t hat o f s ection a nalysis. T his i s w here s amples a re t aken s equentially t hrough a v ertical s ection, o r t hrough c hronostratigraphically d istinct l ayers. T he a dvantage o f s ampling i n t his m anner i s t hat a ny g ross d ifferences i n t he l ayers c an b e a ttributed t o c limatic o r e nvironmental c hange. I f t his S EM a nalysis i s a llied t o s ome g eochronometric d ating t echnique s uch a s U ranium/Thorium d ating, d etailed i nterpretations o f t he e nvironment ( involving b oth c limate a nd m odes o f s ediment t ransport) c an b e a scribed a n a ctual d ate. I t

i s m ost

i mportant

t o

f ollow t he c orrect l aboratory p reparation

t echniques f or t he s ediment, s ince i t i s p ossible t o i ntroduce i nadvertent o perative b ias i n b oth t he c leaning a nd s election o f q uartz g rains f or S EM a nalysis t hat w ill p rejudice t he f inal r esults. T o i nsure m eaningful i nterpretation o f t he q uartz s ediment, a t l east 3 0 t o 5 0 g rains m ust b e a nalysed ( Tovey a nd W ong, 1 978). T hese g rains m ust b e p icked f rom t he r esidue o f t he t reated s ediment. F irstly, f ive g rams o f t he r aw s ample s hould b e b oiled i n 1 0% h ydrochloric a cid f or 2 0 m inutes a nd t hen t horoughly w ashed i n d istilled w ater. T o t he s ediment i s t hen a dded d ilute s odium h exametaphosphate ( Calgon s olution). T he m ixture i s t hen s haken a nd w ashed i n m ore d istilled w ater. I f t he g rains a ppear p articularly r ed i n c olour, i t i s l ikely t hey a re c oated w ith i ron o xide. T his c an b e r emoved b y b oiling t he m aterial i n a s tannous c hloride s olution f or 2 0 m inutes. F ollowing f urther w ashing i n d istilled w ater, t he s amples a re t hen a ir-dried o r g ently o ven-dried a t l ess t han 4 0"C. F rom t he r esidue, b etween 3 0 t o 5 0 q uartz g rains s hould b e s elected ( see B ull, 1 978) a nd m ounted o n s pecimen s tubs s uitable . for t he p articular S EM b eing u sed f or t he a nalysis. B efore m achine a nalysis, t he s tubs s hould b e c oded, p referably b y s ome p erson o ther t han t he S EM r esearcher. T his d ouble b lind t est e nables a ccurate a nd c onfident p redictions t o b e m ade a t t he i nterpretive s tage w hen a ll t he s amples h ave b een a nalysed. T he g rains m ounted o n t he s tub a re t hen s putter-coated w ith a t hin l ayer o f g oldp alladium o r c arbon. D uring S EM v iewing i t i s m ost i mportant t o u tilize t he t ime o n t he m achine t o t he f ullest. T his n ormally i nvolves s ome f orm o f c heck l ist o f f eatures. T here a re p erhaps s ome 5 0 o r m ore t extures t hat h ave b een r ecognized, a lthough f or a ny p articular s ample i t i s u sual t hat o nly t he p rimary 3 0 o r s o b e i nvestigated. T able 1 p resents s ome s urface f eature c ategories t hat a re c ommonly f ound o n s and g rains. T hey a re d ivided i nto t he m echanical f eatures, m orphological f eatures, a nd c hemical f eatures. T he m echanical f eatures i nclude m odifications s uch a s g rain b reakage, e dge a brasion, c onchoidal f ractures, s tepping,

1 07

s triations a nd g rinding f eatures. T hese a lterations m ay h ave b een f ormed b y t he l ast t ransport m echanism ( e.g. w ater, w ind o r g lacier), o r m ay i ndeed b y i nherited f rom a p revious c ycle o f s edimentary e rosion. I t i s a lways i mportant, h owever, t o a scertain w hether t he t extures d erive f rom t he f irst c ycle q uartz, t hat i s q uartz t hat h as c ome f rom a n earby g ranitic s ource. T here h as b een m uch c onfusion i n t he p ublished l iterature c oncerning t he d ifferentiation b etween f irst c ycle q uartz t extures a nd t hose d erived f rom g lacial g rinding. T he r eader i s u rged t o c onsult t he f ollowing r eferences f or c larification ( Krinsley a nd T akahashi, 1 962; K rinsley a nd D onahue, 1 968; M argolis a nd K ennet, 1 971; K rinsley a nd D oornkamp, 1 973; W halley a nd K rinsley, 1 974; E yles, 1 978). T he m orphological s urface f eature c ategories l isted i n T able 1 g ive s ome i ndication o f t he r oundness, a ngularity, a nd g eneral r elief o f t he s urface o f t he g rain. T hese c ategories c an b e a ltered a s r equired. T he c hemical f eatures a re m ore v aried a nd i nclude b oth p recipitation a nd s olutional f eatures. M any o f t hese c hemical f eatures h ave r ather e xotic n ames, i ncluding s caling, c arapace, e uhedral c rystals, c hattermarks, d ulled s urface, a nd a nastomosis. T he r eader i s u rged t o c onsult K rinsley a nd D oornkamp's

( 1973) e xcellent a tlas.

F or l aboratory a nalysis, T able 1 w ould i nclude t he t extures a s s et o ut i n t he h orizontal r ows. H owever, t he v ertical c olumns c omprise 3 0 t o 5 0 b oxes, e ach o f w hich r epresents o ne g rain t o b e a nalysed. T able 2 , however, c ontains a gglomerated s urface f eature p ercentages, p ortrayed i n a v isual m anner. U sing s uch a d ata p resentation f ormat, m any t housands o f o bservations c an b e p rovided i n o ne d iagram . I ndeed t he s urface f eature d iagram p resented i n G oudie a nd B ull ( 1984) c overs one page, y et s uccinctly s ummarizes s ome s eventy-six t housand o bservations. N ot o nly i s t he e ditor k ept h appy b y s uch b rief p resentation b ut t he p ublication o f s uch d ata p rovides f or l ater r ee valuation b y o ther r esearchers. T ogether w ith t he S EM m icrographs a nd l aboratory n otes, e ven t he m ost d etailed a nd s eemingly u nimportant m aterial c an b e p rovided f or l ater a nalyses. T his e nsures, w hen a v aluable a rchaeological s ite i s s ampled, t hat t he d ata c ollected c an b e r ecorded f ully a nd p ublished.

I nterpretive P rocedures O nce t he l aboratory a nalysis h as b een c ompleted a nd t he c heck-list ( Table 2 ) h as b een c ompiled, i nterpretation o f t he r esults c an b e u ndertaken. T able 2 p rovides d etail o f a nalyses c arried o ut o n a s et o f s amples t aken i n s ection t hrough T abun C ave, M ount C armel, I srael a nd w ill b e u sed t o i llustrate t he i nterpretive t echnique. T he t able p rovides f ine d etail o f s ome 4 2,500 o bservations a nd m easurements, y et a llows u p-section v ariation i n e nvironmental h istory t o b e p lotted. T abun C ave w as i nitially e xcavated b y G arrod a nd B ates ( 1937) t o a d epth o f 1 6 m etres. T hey i dentified s even c ulturostratigraphic l ayers b ased p rimarily o n a rchaeological e vidence. T he s ampling u sed f or t his a nalysis w as u ndertaken b y G oldberg f rom J elinek's ( 1981) e xcavations a nd i s b riefly d escribed i n B ull a nd G oldberg ( 1985). T able 2 p rovides 2 5 s ample l ayers w hich c orrespond t o G arrod a nd B ates' ( 1937) s tratigraphy

i n

t he

f ollowing

m anner

1 08

( Bull

a nd

G oldberg

f irst):

Table t he

1 .

T ypically u sed

c ategories

a re

t o

S EM t he

" score

c hart".

r ight,

w hilst

r epresents e ach g rain i n t he s ample.

3 4 . C ha t te rma rks 3 .E uhed r a ls i l ca 3 2 .A mo r phous p t . ( s i l i c a ) 3 1 .C a rapac e 3 0 .S ca l ing 2 9 .S o lu t ion c r evas se s 2 8 .S o l u t i on p i t s 2 7 .D u l l ed s u r fa ce 2 6 .A na s t omos i s 2 5 .O r i en ted e t ch p i t s 2 4 . H i gh r e l ie f 2 3 .M ed ium r e l i e f 2 2 . L ow r e l i e f 2 1 .A ngu l a r 2 0 .S ubangu l a r 1 9 .S ub rounded 1 8 .R ounded 1 7 .D i sh shaped c o ncav i t i es 1 6 .M echan i ca lV p i t s 1 5 .C u r ved s c r a t che s 1 4 . S t r a igh t s c r a t ches 1 3 .M eande r ing r i dges 1 2 . F r a c tu r e p l a t es 1 .A dhe r ing p a r t i c l es 1 0 .I mb r i ca t e g r ind ing 9 .P a ra l le l s t r ia t ions 8 .A r cua t e s t eps 7 .S t ra igh ts t ep s 6 .C oncho ida l s (> 10 p ) 5 .C on cho i da l s ( 10 p ) 3 .B r eakage b l ock s( < 10 p )

S u r f a c e f e a t u r e c a t e g o r i e s

2 .E d ge a b r a s i on 1 .C omp l e t e g r a in b r eakage

J a qwnu a l dw es

1 09

T he t he

s urface f eatures a nd t op

r ow

o f

n umbers

Table i n

2 .

S urface

T abun

C ave,

percentage presence

f eature

Mount

s ummary c hart f or a s ection t hrough d eposits

C armel,

I srael.

E ach

box

c ontains

a c onverted

( summarized i nto c lasses b y g raphical r epresentation)

or

a bsence

o f

s urface

f eature

c ategories

i dentified

o f t he f rom

5 0

grains p er s ample.

1 3

3 3 .E u hed r a ls i l i ca

3 1 .C a rapac e

l if 0

0

3

•

M I

0

N I

D D

3 0 .S ca l ing 2 9 .S o lu t ion c r evas se s

1 3

2 8 .S o l u t i on p i t s

O

2 7 .D u l l ed s u r f ace

0

I

o p• . D 1 3

2 6 .A na s t omos i s 2 5 .O r i en ted e t ch p i t s

E l

2 4 .H i gh r e l ie f

•

2 3 .M ed ium r e l i e f

B

2 2 . L ow r e l i e f

D

2 1 3

-

3




•

. 1P t irow e

4

•

.

2

5

1 93

. ,••• ••

•••e s ., • •• ••• ‘ . . . . . . -,0 4 2 .7 . z ie s, _ •,'4 t r . eej . . 1 l e *" 4 8 7 .5 rti t* 4

: f te . " = P i..

t :

S i

P late 2 . Fig.

7 .

S tratum

T ransverse 3 a t

phloem i sland Fig.

f racture

S iphiso, ( top,

s howing

l eft);

o f

C ombretum

t hick-walled,

a piculatum o val,

c harcoal

f rom

s olitary v essels a nd

x68.

8 .

T ransverse

f racture

o f modern,

9 .

Tangential

l ongitudinal

c harred

C ombretum a piculatum;

x68. F ig.

h eterophylla, Fig.

1 0.

T ransverse

s howing

g elatinous

between

t he

o uter; Fig.

f racture

o f modern,

c harred M aytenus

s howing c rystals i n r ay parenchyma c ells; f racture f ibres.

t hick,

i nner

o f

modern,

I n

t hese

wall

l ayers

x 268.

c harred D ichrostachys c inerea,

f ibres, w hich

t here h ave

i s

a l arge

s eparated

s pace

f rom

t he

x 535.

1 1 I nter-vessel p its

s howing

r emains

o f

i n l egume c harcoal f rom S tratum 3 a t S iphiso,

l ignin-rich

v esturing

a round

f racture

Androstachys

t he

p it

a perture;

x 2135. Fig.

1 2.

T ransverse

S tratum 5 a t S iphiso,

o f

j ohnsonii

c harcoal

f rom

s howing h omogenisation o f i nter-cellular material

w ith r esultant l oss o f s tructural d etail; x 268.

1 94

1 95

TABLE 1 .

C harcoals f rom S iphiso.

STRATA

APPROXIMATE DATE

TOTAL NO.

% LEGUMES

FRAGMENTS

( MIMOSOIDEAE)

% C OMBRETUM APICULATUM

1 +2

l ast

1 00 yrs.

2 61

4 2.9

2 7.6

3

Late Holocene

1 34

4 7.8

2 6.9

4

Mid Holocene

9 1

5 0.5

2 2.0

5

Early Holocene

1 19

6 3.0

1 0.1

TABLE 2 .

Fuelwoods Represented a t S iphiso.

S PECIES RANKED I N ORDER

DENSITY

OF DECREASING DENSITY

VALUES G .CM.

% F IBRE WALL *

CALORIFIC VALUES KG.G.

3

D ICHROSTACHYS C INEREA

0 .88

5 2.9

ACACIA CAFFRA ( D)

0 .70

6 0.2

ACACIA CAFFRA ( M)

0 .68

4 9.4

COMBRETUM API C ULATUM

0 .68

4 0.5

ACACIA KARROO

( D)

0 .66

5 8.3

ACACIA KARROO

( M)

0 .66

5 0.6

1

2 0.7

1 8.6

ACACIA N IGRESCENS

( D)

0 .64

5 5.8

ACACIA N IGRESCENS

( M)

0 .62

4 2.7

2 0.3

0 .52

3 4.0

1 9.3

ACACIA TORTILIS D =Drier Provenance M=Moister P rovenance

* =Average a rea of f ibre wall x % total f ibres microscope f ields.

1 96

i n a t l east 5 0 high power

s imilar Many

s ituation

c harcoal

c ellular

s eems

t o

f ragments

s tructure

a nd

h ave

o btained

s howed s ince

c harred

c harred

f ungi must b e i n primary d eposition. o ften

f orm

s tructure

part may

o f

t he

n ot

c harcoal

b e

f ully

a t

S iphiso

f ungal

w ood

i s

i n

hyphae

t otally

p ast

t imes.

w ithin

t heir

i norganic,

t he

S mall t wigs, presumably k indling,

s pectra

a nd

d eveloped

t hough

( Jane,

t heir

1 970),

a natomical

t his

d oes

n ot

g enerally preclude s ecure i dentification. M uch

i nformation

c oncerning

t he

c harring

r egime

u sed

o n

a ncient

s ites c an b e g ained f rom a c omparative s tudy o f e lectron m icrographs o f a ncient

material

a nd

k nown c onditions. wood w as s tate

t hose

f rom

p ublished b y B eall

t hat

polymers,

o n

c harring,

w hich

s imilar

modern

w oods

c harred

u nder

A c omprehensive r eview o f t he t hermal d egradation o f

d egrade

a nd E ickner

w ood

a t

( 1970).

b ehaves

d ifferent

a s

S locum e t a l.

a

mixture

o f

( 1978),

i ts

t hree

t emperatures a nd r ecombine i nto a

c arbonaceous s tructure. Many w orkers u sing S EM t echniques h ave d emonstrated c ellular d eformations w hich a re d istinct f rom t hose c aused by s imple s hrinkage,

a nd a re t he r esult o f s ome d egree o f p lastic f low.

A s Z icherman a nd Williamson ( 1981:247) s tate, " Such f low w ould b e a r esponse t o t he t hermal s tresses w hich a re a pplied t o t he s oftened l ignin

i n

t he

c ellulose

d egrading

r einforcing

c ell

walls

n etworks.

w hich

T hus,

n o

l onger

o ne

c an

c ontain

e nvision

f unctional

t he

o bserved

d eformations a s a c ombined r esult o f p lastic f low d uring t he c ombustion process

a nd

o f

volatilization s uch

s hrinkage

o f

c ell

d eformations

c aused

wall

a re

b y

particularly

v estured pits o f l egumes

volumetric

c onstituents".

I n

e vident

( Ohtani e t a l.,

l oss t he

b oth

1 984),

o f

w ater

a nd

S iphiso material,

i n

t he

l ignin-rich

a nd i n t he t hick walled

A ndrostachys f ibres s hown i n P late 2 .

Application of Results to t he Present Fuelwood Crisis T he u sing

t ype

S EM

S iphiso,

t he

( Mimosoideae) C learly a s

o f

d etailed

t echniques b ulk o r

o f

a f uel

t he

t o

t herefore, s ource

i nformation o btained

h as

f ar

w ider

f ragments

C ombretum

i t by

w as

b elong

a piculatum

t hese

f rom a ncient

potential

( Prior,

e ither

( see

t o

t he

T able

a reas wood

o f

a natomy

w here h ad

a nd

A frica,

s uccessive

l arge

e cologically a re

i nhabitants.

f ragments

b een

particularly

possible.

F rom t hese,

present A cacia

d uring

t he

n igrescens

e t

w ere

a l.,

t o

1 a nd

P late

T he Mimosoideae

g roup

i n

d istinguish

1 980).

e xamined

w ell

I n

o r

2 ).

a rid

a nd

s emi-arid

t he

i nstances,

c haracteristic

s pecific

i nclude

T he a cacias,

s olely o n

s ome

w here

preserved,

basis

o f

h owever, f eatures

i dentifications

w ere

i t was e vident t hat t he r ange o f A cacia s pecies

H olocene

a nd

i mportant

d ifficult

( Robbertse

A t

L eguminosae

g roups t hat w ere c onsistently s elected

D ichrostachys c inerea a nd a w ide r ange o f A cacia s pecies. a w idespread

c harcoals

1 985).

A cacia

i ncluded

A cacia

t ortilis,

a ll

c affra,

s pecies

A cacia

karroo,

o ccurring

i n

t he

v icinity o f t he s helter t oday. W hat i n

t heir

c hange?

t hen w ere c onsistent A ll

w ere

t he

c haracteristics

s election

a nd

o f

h ow

which

r esulted

w ithstand

c limatic

a s s hown i n t he p reliminary r esults r ecorded

i n T able 2 . T hey w ould, t herefore, c onsiderable h eat e mission. O ne a ssumes t heir

t hey

d ense w oods w ith a h igh proportion o f f ibres a nd a ll

h ad h igh c alorific v alues,

d uring

t hese woods

d id

c ombustion

was

n on-toxic

1 97

h ave burnt s lowly w ith a t oo, t hat t he s moke produced

a nd

t hat

t hey

d id

n ot

s park

t o

e xcess. c rystals

I t i s probable t hat t he l arge n umber present i n a xial a nd r ay parenchyma

i dentified

u sing

c ombustion

o f

X -ray

t he

d iffraction

w oods.

A s

t echniques,

S hafizadeh

o f c alcium o xalate c ells, w hich w ere

a ffected

( 1984)

t he

a nd o thers

s peed o f

h ave f ound,

c ations s uch a s c alcium r educe t he r atio o f c arbon monoxide t o c arbon d ioxide production, t hereby a ltering t he r ate o f h eat r elease. A n

u nexpected

m ajority o f

t he

a nd

persistent

a natomical

f ragments

f rom t hese

c harcoal

o f l arge a mounts o f g elatinous f ibres S EM

( see

P late

proportion w alls,

o f

a re

( Hughes, present

2 ).

T hese

hydrophilic

k nown

1 965). s uggested

t o

( G-fibres),

d ense,

modified

c elluloses

o ccur

i n

a nd

t ension

I n

t he

a n

a dditional

present

A cacia

f rom w et t hat

c affra, a nd

t he

n umber

material, t he

was

n umber

f ragments

A cacia

k arroo

d ry provenances. o f

G -fibres

e nhanced by

o f

G

a nd

f rom e ach

a nd

o f

t he

d rought

t he

a ridity i n

t he

t o

t heir s tress

q uantity T wo

branchwood s amples

T able o f

a nalysed

e nhanced

l arge

w ere

p ercentage

s amples

5 was

a n

w ithin

p reliminary ( see

i n

p resence

t olerance.

A cacia n igrescens

h ence

1 t o

w ith

a r esponse

F irstly,

c ase,

f ibres

S trata

a s

h owever,

t hat

e ach

i ncreased

n on-G

o f

a nd

I n

t he

c learly v isible u nder

f ibres

wood

i nstance

r ole,

present

was

h emicelluloses

l ines o f e vidence s upport t his h ypothesis. o f

f eature g roups

3 0

c ollected

s tudies s how

o f

f ibre

2 ).

w all

S econdly,

a ncient

( see F ig.

l egume

1 3).

T he

c onsiderable i ncrease i n t he r atio o f t he G t o n on-G v ariant i n S tratum 4 s uggests

t he possibility o f

d rier

c onditions

b etween

a bout

4 000

a nd

s tressed

t he

6 000 b p. R ecent s everity

FAO

o f

marginal, B otswana,

a nd

t he

World

present

B ank

r eports

f uelwood

h ave

c risis,

f requently w hich

i s

most

a cute

i n

s emi-arid l ands w here population p ressures a re g reatest. eastern S waziland, Z ambia a nd Z imbabwe a re a mong t hose a reas

c urrently a t r isk. A ll t he t rees m entioned a s f uelwoods a t S iphiso a re i ndigenous t o t hese r egions. A s s uch, • they a re f amiliar t o t he A fricans

w ho,

b eing

g reatly

d ependent

t hese s ame woods f or f ires t oday. f odder,

s hade,

s oil

f orestry projects o f

f ast

g rowing,

r ainfall. N ew f old

T he

n on-indigenous

i n

magic

s outhern A frica

N airobi

a nd R enewable i ncrease

e nrichment,

i n

a nnual

t raditions,

a nd m edicine.

s pecies

s elect

O f

r ecent

y ears,

i n a reas o f c omparatively h igh a dopted a t t he U N C onference o f

i n A ugust

r ate

o ral

t hey a lso u se t he t rees f or

h ave c oncentrated u pon t he growth

P lan o f A ction,

E nergy R esources t he

u pon

F urther,

o f

t ree

1 981,

r ecommends

p lanting

i n

a f ive-

d eveloping

c ountries by t he y ear 2 000. D uring t he n ext d ecade t herefore, i t w ould perhaps b e a ppropriate i f t hose i ndigenous s pecies a lready s hown by t he a rchaeological

r ecord

t olerance,

u sed

w ere

t o

b e

d esirable

f uels

f or w ide-scale p lanting

a s a n i ndividual basis.

1 98

o n

a nd

t o

h ave

a c ollective,

d rought a s

w ell

Fig.

1 3.

T o ta ls o f Ge la t inous ( Wh ite ) a nd Non -ge la t inous ( Shaded ) F ibres I n S amp les o f 3 0 Anc ient F rag men ts

2 3 2 1

1 7

9

7

4

1 /2

1 4

3 S TRATA

1 99

5

Acknowledgements F unding S waziland

f or

t hese

N ational

C hairman 's F und L ondon. D r. D .

s tudies

T rust

i s

g ratefully

C ommission,

t he

a cknowledged

Anglo

f rom

American

d e

t he

B eers

a nd t he C entral R esearch F und o f t he U niversity o f P rice W illiams w as r esponsible f or e xcavation o f t he

S iphiso s ite a nd D r. K . A lvin c ollaborated i n t he w ork l eading t o t he p reliminary r esults r ecorded i n T able 2 . M any m embers o f t he D epartment o f P ure a nd A pplied B iology, I mperial C ollege, p articularly P rofessor J .

L evy,

M r.

N .

C osta a nd M rs.

M .

D ocherty,

provided h elp a nd

a dvice d uring t he c ourse o f t he w ork. R eferences A cocks,

J .P.H.

1 975.

V eld

t ypes

o f

B otanical S urvey o f S outh A frica 4 0: B eall,

F .C.

a nd

c omponents:

a

E ickner,

r eview

R esearch P aper F PL: B eall,

F .C.,

p hysical

H .W .

o f

t he

S outh

A frica.

M emoirs

o f

t he

1 -128.

1 970.

T hermal

l iterature.

d egradation

U .S.D.A .

F orest

o f

w ood

S ervice

1 30.

B lankenhorn,

properties

a nd

P .R. u se

a nd M oore, a s

a n

S EM

G .R.

1 974.

C arbonized w ood-

preparation.

Wood

S cience

6 :

2 12-219. D eacon,

H .J.

t he

U pper

1 0:

2 41-257.

1 979.

D eacon,

H .J.,

s ource

o f

D eacon,

Excavations

P leistocene

S choltz,

A .

H endy,

P alaeoecology:

a

B oomplaas

L .D.

a nd

P reliminary

T .

1 982.

T wo

l ater

S ynthesis,

i ron

Nature R eserve, L etaba d istrict, A rchaeological B ulletin 3 7: 6 3-67. G oldblatt,

P .

1 978.

c haracteristics,

G oudie,

A .S.

H ughes,

a nd

1 965.

J ane,

F .W .

a nd C .

F ynbos

J .J.N.

r egion.

I n

( eds.),

Fynbos

S outh

A frican

1 74-182.

a ge

s ites

N .E.

o n Mabete,

T ransvaal.

Hans

Merensky

S outh

A frican

o rigins.

Annals

o f

t he

i ts

M issouri

D .

1 983.

T ension w ood:

T he A tlas o f S waziland. O ccasional P aper n o.

a r eview

o f

l iterature.

4 . F orestry

2 -9. 1 970.

T he

S tructure

o f Wood,

s econd

e dition.

L ondon:

A .

n eck:

t he

B lack.

J elenic,

N .E.

f irewood

s ituation

N ote 5 :

F ossil c harcoals a s a

t he

3 69-436.

a nd P rice W illiams,

F .E.

t hrough

7 5.

T he S waziland N ational T rust C ommission.

A bstracts 2 6:

p p.

s equence

World A rchaeology

A n a nalysis o f t he f lora o f s outhern A frica:

r elationships

B otanical Gardens 6 5:

i n

L ambrechts,

N ational S cientific P rogrammes R eport: E vers,

1 983.

i nformation

Q .B.

C ave-a

i n S outh A frica.

a nd Daitz,

palaeoecological

H .J.,

a t

a nd H olocene

a nd

G aborone,

v an i n

V egten,

J .A.

s outh-western

1 981. K gatleng,

Botswana.

2 00

A pain

i n

B otswana.

t he

N IR R esearch

L eney,

L .

a nd

C asteel,

R .W.

c harcoal s pecimens S cience 2 : 1 53-159.

f or

M urdoch,

S oils

G .

1 970.

1 975.

S implified p rocedure f or e xamining

i dentification.

a nd L and

J ournal

C apability

i n

o f

Archaeological

S waziland.

Mbabane:

S waziland M inistry o f A griculture. O htani,

J .,

M eylan,

B .A .

a nd

w arts - proposed t erminology.

P rice W illiams, D . 1 980. A rchaeological B ulletin 3 5: P rior,

J .

1 983.

S waziland,

u sing

I nternational B alkema . P rior,

o f

1 985.

Products

t echniques. t he

i n

C .S.I.R.,

P rior,

K .L.

a nd A lvin,

1 984. 5 :

S waziland .

J .C.

c harcoals

pp.

a nd f rom

P retoria,

1 983.

pp.

c harcoals

( ed .),

H emisphere,

o r

S outh A frican

a rchaeological

1 983,

V estures

3 -8.

P roceedings

s ignificance a nd

o f

a n

R otterdam :

S waziland.

1 6-14,

f rom

L ate C ainozoic

3 53-360.

International-Achievements

P roceedings volume 1 , J .

i n

i dentification

a rchaeological

Research

on

S waziland,

T he

B .G.

I n Vogel,

S outhern

S ymposium,

J .

r epresented

A rchaeology 1 3-18.

I nvestigations

S EM

Palaeoclimates

B utterfield,

I AWA Bulletin n .s.

o f I n

t he

w oods Forest

F uture,

1 -16.

S tructural c hanges o n c harring w oods

o f D ichrostachys a nd S alix f rom s outhern A frica.

I AWA B ulletin n .s.

4 :

1 97-206. P rior,

J .

a nd A lvin,

K .L.

1 986.

S tructural c hanges o n c harring woods

o f D ichrostachys a nd S alix f rom s outhern A frica: c ontent. I AWA B ulletin n .s. 7 : 2 43-250. P rior, c hange

J .

a nd

i n

P rice W illiams,

t he

H olocene

S waziland, 4 75.

s outhern A frica .

R obbertse,

P .J.,

V enter,

D .

e poch

G .

1 985. u sing

i nvestigation o f c limatic

a rchaeological

c harcoal

J ournal o f A rchaeological S cience 1 2:

a nd

van

R ensburg,

a natomy o f t he S outh A frican a cacias. S alisbury, E .J. a nd J ane, their s ignificance i n

An

t he e ffect o f moisture

H .J.

1 980.

I AWA Bulletin n .s.

1 :

J ournal o f E cology 2 8:

3 10-325.

S cott, L . 1 982. A l ate Q uaternary pollen r ecord f rom t he b ushveld, S outh A frica . Q uaternary R esearch 1 7: 3 39-370.

S eries 2 07:

4 90-529.

T ransvaal

T he c hemistry o f pyrolysis a nd c ombustion. I n C hemistry o f S olid Wood. Advances i n C hemistry American C hemical S ociety,

S locum, D .H., M cGinnes, E .A . y ield, s hrinkage, a nd d ensity h ickory woods.

T he wood 9 3-103.

F .W . 1 940. C harcoals f rom M aiden C astle a nd r elation t o t he v egetation a nd c limatic

c onditions i n prehistoric t imes.

S hafizadeh, F . 1 984. R owell, R . ( ed.), T he

f rom 4 57-

Wood S cience

Washington,

D .C.

J r. a nd B eall, F .C. 1 978. C harcoal c hanges d uring c arbonization o f oak a nd

1 1:

4 2-47.

2 01

Tusenius, M.L. 1986. The study of charcoal from some southern African archaeological contexts. M.A. thesis, University of Stellenbosch. United Nations. 1981. Report of the Renewable Energy Sources, New York.

UN

Conference on New and

van der Merwe, N.J. and Killick, D.J. 1979. Square: an iron smelting site near Phalaborwa. South African Archaeological Society, Goodwin Series 3: 86-93. van Zinderen Bakker, E.M. 1978. Quaternary vegetation changes in southern Africa. In Werger, M.J.A. (ed.), Biogeography and Ecology of Southern Africa. The Hague, Junk, pp. 133-143. Zicherman, J.B. and Williamson, R.B. 1981. Microstructure of wood char. Part 1: Whole wood. Wood Science and Technology 15: 237-249.

202

S EM AND T HE I DENTIFICATION D OMESTICATION I N S EED P LANTS B ruce D .

O F

M ICRO-MORPHOLOGICAL

I NDICATORS

OF

S mith

I ntroduction I dentifying

P rehistoric

C ultigens.

T he

i nitial

e mergence

a nd

s ubsequent e laboration o f p rehistoric f ood p roduction s ystems c entering o n c rop p lants w ere d evelopments o f p rofound i mportance i n t he c ultural e volution o f h uman p opulations i n m ost a reas o f t he w orld. G aining a n u nderstanding o f t he i ncipient s tages o f p rehistoric c ultivation o f c rop p lants b y h uman p opulations h as b een h ampered, h owever, b y d ifficulties i nherent i n a ttempting t o i dentify i n t he a rchaeological r ecord t he c hanging T his d ifficulty i n

n ature o f p rehistoric i dentifying i ncipient

h uman-plant r elationships. c ultivation o f p lants i s

e vident i n t he r elative w eakness o f t he i ndirect a rguments o ffered i n s upport o f a ssigning " cultivated" s tatus t o p lant s pecies r ecovered i n a rchaeobotanical a ssemblages. P lant s pecies a re u sually d esignated p rehistoric c ultigens o r " quasi-cultigens" o n t he b asis o f o ne o r m ore o f t he f ollowing a rguments ( see S mith 1 985a f or r eferences r egarding t he a pplication o f t hese c riteria): 1 . T he e xistence o f m odern w eed a nalogs f or a p lant s pecies; 2 . A p rehistoric r ange e xtension f or t he p lant s pecies; 3 . T he a rchaeological a bundance o f a p lant s pecies r elative t o i ts m odern o ccurrence; 4 . T he p erceived e conomic i mportance o f a p lant s pecies; 5 . T he c ultivation o f a s imilar s pecies e lsewhere; 6 . A p rehistoric a ssociation o f t he p lant s pecies w ith k nown c ultigens; 7 .

E arly h istorical d escriptions o f c ultivation o f a p lant s pecies; 8 . A d ocumented p rehistoric i ncrease i n a bundance o f a p lant s pecies t hrough t ime; 9 . A n i ncrease i n h uman p opulation l evels a nd s ociopolitical c omplexity, i mplying a n a gricultural e conomy; a nd

1 0.

A d ocumented m orphological c hange i n r eproductive p ropagules ( e.g. s eeds) a ssociated w ith d omestication.

O nly t he l ast o f t hese a rguments, h owever, a llows t he u nequivocal i dentification o f a p lant s pecies a s a c ultigen, a s o pposed t o a n i ntensively h arvested w ild p lant o r w eedy c amp f ollower. W hile t hese o ther a rguments c ertainly s erve t o s trengthen t he c ase f or c ultivated s tatus, t he s ingle u nquestionable i ndicator o f c ultivation t hat c an b e o bserved d irectly i n t he a rchaeobotanical r ecord r emains m orphological c hange i n p lant p ropagules ( e.g. s eeds) a ssociated w ith d omestication. S EM a nd t he I dentification o f M orphological C hange A ssociated w ith t he A daptive S yndrome o f D omestication. R esulting f rom s trong a nd a utomatic s elective p ressures w ithin a n a nthropogenic h abitat, i .e. d isturbed s oil, s uch g enetic-morphological c hanges r eflect a n a daptation t o t he h arvesting a nd s owing o f s eeds b y h uman c ultivators.

2 03

T he n ature o f t hese s elective p ressures a nd t he m orphological c hanges w hich t hey p roduce h ave b een c learly e stablished b y H arlan a nd o thers ( Harlan e t a l., 1 973; d eWet a nd H arlan, 1 975). S eed b ed c ompetition, o n t he o ne h and, a utomatically s elects b oth f or i ncreased s eedling v igor ( frequently r esulting i n i ncreased s eed s ize) a nd r educed g ermination d ormancy ( frequently r esulting i n a l oss o r r eduction o f s eed d ormancy m echanisms, s uch a s t he s eed c oat). I n a ddition, h arvesting, i n a ssociation w ith s uccessive d eliberate s owing, s elects f or u niform r ipening o f t he s eeds, i ncreased s eed p roduction, b etter " packaging" o f s eeds f or t he h arvester ( more t erminalized a nd c ompact i nfructescences), a nd a l oss o f n atural d ispersal m echanisms. Recognizing and documenting these domestication-related m orphological c hanges i n a rchaeobotanical a ssemblages, h owever, i s o ften d ifficult. T he p lant p arts t hat a re n ecessary t o s tudy u niform m aturation, a n i ncreased p roduction o f s eeds, a nd i ncreased c ompaction a nd t erminalization o f s eedheads a re r arely p reserved. A t t he s ame t ime, e ven t hough s eeds a re f requently p resent i n a bundance i n a rchaeobotanical a ssemblages, t he c hanges i n s eed m orphology a ssociated w ith d omestication, r esulting f rom s elective p ressures f or r educed s eed d ormancy a nd s eed d ispersal, a nd i ncreased s eedling v igor o ften i nvolve s uch s mall s cale m odifications i n s eed s tructure t hat a ccurate d escription o r q uantifiable d ocumentation u sing o nly a s tandard l ight m icroscope i s e xtremely d ifficult. I t i s o nly i n t he p ast d ecade, t hrough t he a pplication o f s canning e lectron m icroscopy, t hat t he f ull r esearch p otential o f m icrom orphological a nalysis o f a rchaeobotanical s eed a ssemblages h as b een r ecognized. I n E urope a nd G reat B ritain t he a pplication o f S EM t echnology t o t he s tudy o f s eed m orphology b egan i n t he m id t o l ate 1 970's, a s r epresented b y t he l andmark w ork o f K orber-Grohne ( KorberG rohne a nd P iening, 1 980; K orber-Grohne, 1 981) i n d istinguishing O ld W orld c ereal g rains o n t he b asis o f s urface m icrostructure. A s imilar i nterest i n a pplying S EM t echnology t o t he s tudy o f t he m icrostructure o f a rchaeologically r ecovered s eeds o f N ew W orld d omesticates d eveloped i n t he U nited S tates i n t he l ate 1 970's ( Wilson, 1 981). T o i llustrate t he v alue o f s canning e lectron m icroscopy i n t he r ecognition a nd q uantification o f m icro-morphological i ndicators o f d omestication, c ultivation o f n ote 1 ).

a N orth American e xample i nvolving t he p rehistoric C henopodium b erlandieri w ill b e b riefly s ummarized ( end

A n E xample f rom t he E astern Woodlands E arly C laims

f or D omesticated C henopodium i n

d ebate r egarding w hether o r p resent i n t he p rehistoric e xtended o ver s ix d ecades. A s

e arly

a s

1 926

t he P rehistoric E ast

n ot a d omesticated f orm o f c henopod e astern w oodlands o f N orth A merica

( Asch

a nd

A sch,

1 977:12),

O liver

A w as h as

F reeman

i dentified c henopod s eeds r ecovered f rom B luff S helters i n t he O zarks o f A rkansas a s a p robable c ultivated f orm, d ue t o t heir m orphological s imilarities t o C . b erlandieri s sp. n uttalliae, a m odern M exican c ultivated c henopod. T en y ears l ater, V olney J ones s uggested t hat

2 04

c henopod s eeds r ecovered f rom poorly d ated p rehistoric d eposits a t N ewt K ash S helter, M enifee C o., K entucky, r epresented a c ultivated c rop p lant. H is i dentification o f t hese s eeds a s b eing f rom a d omesticated c rop w as s pecies T he

based on ( Jones,

R ejection

1 970's, t he

e astern

w oodlands

s eeds

C laims

i n t wo r espects

c laims

N orth

America

s eeds

a pparently

" cross-sectional

s hape

S tatus.

t he

O zark

I n

a nd

t he

N ewt

m id Kash

a nd J ones a nd r ejected both o f

f or prehistoric ( Asch

C henopodium

a nd A sch,

f ound

o f

t he s eeds o f w ild

t he

t o

1 977).

a ctually

O zark B luff

i n

T he

b e

t he

l arge

pokeweed

S helter

c henopod

d iffering morphologically f rom w ild s eeds

- a

s pecimens

t o

1 977:14).

Domesticated

w ere

R estudy

( Asch a nd A sch,

a rchaeological

c omparison

r eanalyzed

s tatus

o f

t hem

f or

A sch

a mericana).

s howed

i n

s tudied b y F reeman

" chenopod"

( Phytolacca

s ize

A sch a nd A sch,

N ancy

c ultigen

K ash

l arge

E arly

a nd

a ssemblages

e arlier

N ewt

o f

David

c henopod

t heir

1 936:149;

1 977:19):

t endency

a s

t oward

o pposed

t o

t runcate

published

margins

i n

d escriptions

o f

t he C .

b ushianum a s b iconvex i n c ross s ection. p rominence o f markings o n t he s eed c oat - l ess p rominent o n most a rchaeological s pecimens t han i ndicated by published d escriptions." T he A sches, h owever, a lso o bserved t hese morphological t raits ( truncate margins a nd v ariable s eed c oat markings) i n a s ignificant p ercentage o f t he f ruits produced by a modern, l ate s eason s tand o f w ild C .

b ushianum w hich t hey s tudied i n t he m id-1970's.

r elative

a bundance

studied,

A sch

o f

a nd

s uch

" red morph"

A sch

c oncluded

B ecause o f t he

f ruits i n t he modern w ild s tand t hat

r ather

t han

i ndicating

d omestication, t hese morphological c haracteristics o f t he prehistoric Ozark specimens could b e e xplained a s r eflecting p henotypic polymorphism s pecific

t hickness,

i n

w ild

a nd

i ndicator ..

i n

mention o f

f ound

made

t his

o f

s tatus.

c onvincing

N orth

American

F irst

h owever,

Application

H ugh Wilson

c onvincingly form

of

Employing

c ross-sectioned

s eeds

Mexican

' huauzontle',

t o

a gain

c )

f or

t he a t

s eed

c hanges

O zark

C .

O zark

t hey

h ad

[ domestication]

I n

t he

l ate

1 970's,

c henopod materials

p resence

B luff

o f

S helter

C henopodium b erlandieri

a rchaeological

a possible

t hat

T his position was

Wilson

c ompared

b erlandieri; s sp.

s pecimens

a nd

a d omesticated a rchaeobotanical

e lectron m icroscopy,

w ild

N o

( testa)

1 980:158).

P roblem .

t he

c oat

a s

c oncluded

( 1977:24).

in a )

( 1977:20-22).

i n

d iscussed

g enetic

p rehistoric

cultivar

a nd

n ot

t he

s canning

o f:

was

( Asch a nd A sch,

S EM

Chenopodium

bushianum

C henopodium"

l ooked

d emonstrated

a ssemblages. modern

o f

C .

T he A sches

e vidence

r eiterated i n a 1 980 a rticle T he

o f

o bserved variation

c haracteristic

d omesticated

n o

Eastern

p opulations

was

b )

n uttalliae

f rom

H olman

t he c v.

B luff

S helter, Madison C ounty, A rkansas. Wilson's c omparative S EM a nalysis s howed t hat w hile t he w ild f ruit h ad a t hick, b lack o uter e piderm s eed c oat

l ayer

( testa),

t his

d ormancy i n t he w ild, M exican

c ultivar

s elective

e limination e vidence modern

a nd t he

pressure o f

f or

t he

t ough

f or o uter

H olman r educed

e ssential f or s eed

" naked"

B luff S helter s pecimens, g ermination

e piderm,

d omesticated

M exican

l ignified s tructure,

a ppeared t o b e e ntirely a bsent i n both t he modern

s tatus

s eeds

a

d ormancy.

d ue t o s trong T his

a pparent

i n a ddition t o p roviding u nequivocal a nd l ight

2 05

g iving

t he

c oloration

a rchaeological

a nd

a s

t he

o pposed

t o

characteristic black coloration of wild fruits, also appeared to result in the truncate marg.in morphology previously recognized by the Asches (Wilson, 1981:237). In comparing the micromorphological structure of prehistoric and modern seeds with the aid of scanning electron microscopy, Wilson demonstrated, for the first time, the critical role that SEM could play in elucidating long standing questions regarding prehistoric plant husbandry in the Eastern Woodlands. A l t h o ugh it was generally thought at the time that the domesticated pale-colored chenopod_ recognized by Wilson was a late p r e h i s t o ric (post A.D. 1200) introduction from Mexico, direct accelerator dating of Ozark specimens has recently shown that the pale­ seeded variety of domesticated Chenopodium was present in Eastern North America by ea. A.D. 300 {Fritz, 1986a, 1986b; Fritz and Smith, 1988). Initial Recognition of a "Thin-Testa" Chenopod. In his 1981 article Wilson also provided a brief, but important, reference to another Mexican cultivar variety of chenopod (Chenopodium berlandieri ssp. nuttalliae cv. 'chia') which retained an outer epiderm (testa) structure that was substantially reduced in thickness in comparison to that of wild species. Within a few years, several researchers would suggest the prehistoric presence of a second domesticated form of chenopod in the Eastern Woodlands of North America, a thin-testa, 'chia'-like taxon. The supporting arguments that would eventually be developed in support of the presence of a prehistoric thin-testa chenopod in the East would, once again, rest on comparative SEM micromorphological analysis of archaeological and modern seeds. In a paper presented in 1982 at the annual meeting of the Society for American Archaeology, Asch and Asch briefly reported on chenopod seeds from the Newbridge and John Roy sites in west-central Illinois. The seeds were described as being: "... morphologically dissimilar to Specifically, they have a truncate seed margin, wild C. bushianum. they have almost entirely smooth seed coats, and they appear to have a thinner seed coat than modern C. bushianum or the other prehistoric chenopods." The Asches here identify additional morphological characteristics that appear to distinguish the prehistoric specimens from modern wild seeds of Chenopodium berlandieri, namely an apparently thinner and smoother seed coat. In addition, the Asches drop their earlier position that the "red morph" characteristic observed in prehistoric specimens of chenopod reflect variation within wild populations and agree with Wilson that: " ...change of morphology through domestication is the most probable explanation for prehistoric samples diverging from typical C. bushianum seed characteristics (Asch and Asch, 1982:11)."

206

T his

c hange

d omesticated b ased

o n

o f

o pinion,

a nd

f orms

f rom

Woodland

f act

t hat

production

t he

m orph" f ruits i n w ild s tands o f C . a p revious

paper,

v ariability

i n

C .

v ariation

i n

f ound

n atural

n o

w e

c ave

s uggested b ushianum

a nd

r ecognition

o f

( Asch

t hin-testa

" apparently 1 982:11)

c ould

possible

1 977) S ince

w ith

f or

T he

f ollowing

S ociety

y ear,

i n

" ...in s imilar

t hen,

more

w e

t han

p ercentage o f s eeds a pproximating t he p rehistoric material." A sch, 1 982:11).

t he

" red

t hat phenotypic

a ccount

c ollections.

populations

w as

t runcate margin

b ushianum w as e xtremely r are: a nd A sch,

b ushianum

o f

a nd A sch,

( Asch

r ockshelter

C .

t he

s ites"

a

h ave s mall

( Asch a nd

a paper presented a t t he a nnual m eeting o f

f or American Archaeology,

R ichard Yarnell

( 1983)

n oted t he

p resence o f c henopod s eeds i n human f ecal s amples f rom S alts C ave, K entucky, w hich were: " lacking t he h ard, b lack o uter c overing." Yarnell w ent

o n

t o

s ay:

" These

f inds

a nd o thers provide

C henopodium b ushianum was i n s ome s tage b eginning d uring t he t erminal A rchaic

u s

w ith e vidence t hat

o f t he d omestication process i n I llinois, K entucky, a nd

T ennessee..." L ater p resence, a t

t he

t he

M iddle

I llinois.

I n

p roduced t runcate

y ear,

Woodland

a ddition

by

w ild

a

s econd

r ecognize T he

s ame

t he

A sches

i n r oughly e qual f requency,

o f

c henopod a s

1 00-250)

c onsider

t he

t hin-testa

C henopodium

t ype

w ell

a gain

r epresented

A .D.

S miling

t he d eeply a lveolate,

s tands

c ross-section,

A sches

( ca.

t o

( 1983:692-695)

having:

a s

r ecount

t he

o f t wo t ypes o f C henopodium s eeds Dan

b erlandieri, " a

s ite,

i n

t hick s eed c oat f ruits t hin

t he

s eed

c oat

A sches with

a

a much s moother s eed c oat s urface."

t he possibility " red morph"

t hat

t hese

t ype produced

t hin-testa i n

l ow

s eeds

f requency

b y w ild p lants,

but r eject t his e xplanation b ecause o f t he a bundance o f

t he

f orm

t hin-testa

u nder

w hich

t he

u nusual o nes. p lants,

o ne

i n

t hin

t he

S miling

s eed-coat

D an

morph

a ssemblage:

predominated

c onditions

t he

I f a rchaeological s pecimens w ere collected

w ould

n ot

e xpect

i n

t heir

1 982

w ild

a re

f rom

w ild

t he predominance o f t hin s eed c oats w hich

c haracterize Woodland p eriod C henopodium ..." W hile

" The i n

paper

t he

( Asch a nd A sch,

A sches

r efer

t o

1 983:694). " apparently

d omesticated" Woodland p eriod C henopodium,

b y 1 983 t hey t ake a s tronger

position

S miling

- t hat

t he

t hin-coated

t ype

a t

Dan

was

" either

t he

p roduct o f i ndigenous d omestication o f C . bushianum o r a n i ntroduction f rom M exico o f a c losely r elated d omesticate." ( Asch a nd A sch, 1 983:695). B uilding

a C ase

f or

D omestication.

B y

1 983

c henopod

f ruits

a ppearing

t o h ave a t hin t esta h ad been r ecognized i n prehistoric c ontexts a t f our e astern s ites ( Salt's C ave, c a. 5 00 B .C .; S miling Dan, c a. A .D. 1 00-250;

N ewbridge,

h ad b een proposed o f a d omesticated E arly,

M iddle,

h owever,

c a .

A .D.

4 80-660;

a nd J ohn R oy,

a nd

Late

Woodland

periods.

I t

t o c ontrol f or p otential s ources o f b ias,

e xplanations, d omesticated

a nd

c a.

A .D.

5 50).

I t

t hat t hese f ruits r eflected t he prehistoric presence f orm o f c henopod i n t he E astern Woodlands d uring t he

e stablish

t hin-testa

a c onvincing

f orm o f

c henopod

c ase

was

s till

n ecessary,

r ule o ut a lternative

f or

t he

presence

o f

a

i n p rehistoric garden s ystems

o f t he E astern Woodlands. A d etailed c omparative micro-morphological a nalysis o f m odern w ild, modern d omesticated, a nd prehistoric c henopod

2 07

f ruits

f ollowing

W ilson 's

g eneral

r esearch

d esign

( 1981)

w as

c learly

r equired. S uch a p rogram o f a nalysis w as c arried o ut o ver a f our y ear period ( 1982-1985).

C ritically

i t

d escribing

f ocused o n

modern

t hick

d ependent a nd

upon

s canning

e lectron m icroscopy,

c omparing c henopod f ruits o f f our g eneral

k inds:

1 )

s tands f ruits

o f C henopodium b erlandieri; 2 ) m odern t hin-testa " red-morph" f rom w ild s tands o f C henopodium b erlandieri; 3 ) modern t hin-

t esta

f ruits

f rom e astern N orth American w ild

t esta f ruits o f t he M exican c ultivar C .

b erlandieri s sp.

n uttalliae c v.

' chia'; a nd 4 ) a rchaeobotanical a ssemblages o f t he t hin-testa c henopod t ype ( Smith, 1 984, 1 985a, 1 985b; S mith a nd F unk, 1 985; S mith a nd C owan, 1 987;

F ritz a nd S mith,

1 988).

Methods T his

c omparative

M icroscope

a nalysis

L aboratory

o f

w as

t he

c onducted

National

a t

t he

Museum

o f

S canning E lectron Natural

H istory,

S mithsonian I nstitution, on C ambridge S tereoscan 1 00 i nstruments. modern s tub t o

a nd prehistoric

s lides

w ith

provide

d ouble

D uPont's

a b etter

s ided

t ape,

s pecimen l oss.

s eed

s pecimens

E lvace

a nd

1 874.

l onger

r esulting

O nce m ounted,

T his l iquid a dhesive w as f ound

l asting

i n

l ess

a ttachment

c harging

t o

o f

S EM

s tubs

s pecimens

t he

o f

b est

g reater

g old-palladium . r esults

t han

C ambridge

w ithin

A n

t he

2 000-2500X).

S tereoscan

1 00

t han

a nd

l ess

s pecimens w ere f irst g iven a b ase c oat o f

c arbon, which i nsured a more u niform a pplication o f a s econd, c oating

Both

w ere f irst a ttached t o g lass S EM

a ccelerator v oltage

r ange

o f

B uilt-in a llowed

o f

magnification m easurement

r apid

a nd

1 0

o verlying

K v produced

employed

( rarely

c apabilities

a ccurate

o f

t he

d etermination

o f

t esta t hickness values f or c henopod s pecimens. O ne

o bvious

c henopod

f ruits,

t hickness

varied

a lternative s uggested i n

e xplanation i n

t he

f or

e arly o f

prehistoric

1 980's,

w ild

populations

C .

w ith

s outhern populations

was

berlandieri,

t hin-testa t hat

t esta

e ither

a long

g eographical

c lines,

t hinner

s eed

c oats,

g rowing c oats.

i n s hady o r w et s ettings producing f ruits h aving t hinner s eed I n o rder t o e valuate t his possibility, C henopodium b erlandieri

s tands

w ere

o r

h arvested

i n

f rom a w ide

a cross t he e astern U nited S tates T esta

t hickness

f ruits,

d etermined

( Smith,

1 985a,

v aluds

t hrough

1 985b).

producing f ruits h aving

r esponse t o h abitat variability,

o f

r ange o f

d ifferent

( Smith,

1 987).

s amples

o f

S EM

a nalysis,

T hickness

values

t he o f

habitat

c ollected

r anged t he

w ith s tands

f rom

s ettings

m odern

4 0-80

measured

w ild

m icrons

w ild

s tand

f ruits w ere d etermined t o b e u ninfluenced by e ither l atitude o r h abitat s etting. I n c oats

o f

d ramatic f ruits

c ontrast, o f

t he

w hen

M exican

c ross-sectioned c ultivar

a nd

m easured,

C henopodium b erlandieri

n uttalliae c v. ' chia ' ( provided b y H ugh t hickness v alues i n t he 1 0-20 m icron r ange.

W ilson),

y ielded

s eed s sp. t esta

S imilar S EM a nalysis o f s amples o f " red morph" f ruits f rom I llinois, M ichigan, a nd S outh C arolina s tands o f C . b erlandieri s howed testa

thickness

values

r anging

2 08

f rom

7 -30

m icrons,

o verlapping

c onsiderably w ith t he 1 0-20 c henopod c ultivar " chia".

m icron

r ange

d ocumented

f or

t he

M exican

S EM a nalysis a lso s uggested t hat " red morph" f ruits c ould b e d istinguished f rom t he t hin-testa d omesticate f ruits o n t he basis o f g reater p itting o f t he t esta s urface o f t he f ormer. I n a ddition, " red morph"

f ruits

w ere

s hown

t o b e produced o nly

i n v ery

l ow f requencies,

c omprising 1 -3% o f t he t otal f ruit p roduction o f w ild C . berlandieri s tands ( Smith, 1 985b:122). N evertheless, t he o verlap i n t he r anges o f " chia" a nd " red morph" t esta t hickness values underscored t he n ecessity o f l ocating a nd a nalyzing l arge, unmixed, t hin-testa a rchaeobotanical c henopod a ssemblages i n o rder t o e stablish a c onvincing c ase f or t he p rehistoric

presence

o f

a

" chia"-like

d omesticated

c henopod

i n

t he

E astern Woodlands. T wo p reviously u nanalyzed museum c ollections o f C henopodium f ruits p rovided t he

a n

e xcellent

o pportunity

m icro-morphology

o f

t he

t o

d ocument,

prehistoric

t hrough

t hin-testa

S EM a nalysis,

c henopod

o f

t he

E astern Woodlands. T he

R ussell

e xcavated o f

C ave

i n

a nd A sh

R ussell

c arbonized

C ave A ssemblages.

C ave,

i n

1 956,

s eeds.

A

s ample

C henopodium

u ncatalogued a nd u nanalyzed R ussell N MNH

c ollections

R ussell t hree

C ave

i n

i mportant

t hick-testa

1 982.

c henopod

C ave

S ubsequent

a ssemblage

f acts.

c henopod

A g rass-lined

Alabama,

F irst,

s eeds.

t here

o f

s torage p it

a l arge

volume

a pproximately

5 0,000

c henopod s eeds was l ocated i n d etailed

( Smith,

S econd,

c ontained

was

S EM

1 984,

a nalysis

1 985a)

a c omplete

t esta

a bsence

t hickness

o f

t he

d emonstrated

values

o f

a ny

o f

7 -16

m icrons w ere c omparable t o " chia" a nd c onsiderably l ower t han t he 4 0-80 m icron

r ange

T hird,

t here w as a c onsistent o ccurrence o f a d istinctive s et o f micro-

o f

morphological

t he

f eatures,

t runcate margin, t esta

o f

modern

n otably

t hese

c ultigen

t o

f eatures

s trong

w ild

s tands

a r ectanguloid

a nd a s mooth t esta.

t hickness,

c henopod

f ruits

f ruit

C .

b erlandieri.

c ross-section,

a

When c ombined w ith a r eduction i n

r epresent

s eed

o f

b ed

a n

a daptive

s elective

r esponse

pressure

f or

by

a

r educed

g ermination d ormancy ( Figures 1 , 2 ). A s ample o f t he R ussell C ave s eeds provided a particle a ccelerator ANS) d irect d ate o f 2 ,340 + /- 1 20 B .P. Excavated Museum, y ielded

i n

1 876

a nd

c urated

H arvard U niversity, t he a n ANS d ate o f 1 ,720 + /-

analysis of approximately morphological s election a ssemblage.

a c entury by

t he

P eabody

the well-preserved, uncarbonized a ssemblage o f 2 5,000 s eeds d ocumented t he s ame s et o f m icrof eatures

f or

f or o ver

A sh C ave, O hio, c henopod a ssemblage 1 00 B .P ( Smith, 1 985b). D etailed S EM

r educed

T esta

a ssociated

g ermination

t hickness

w ith d ormancy

values

a n

a daptive

s een

i n

t he

r esponse R ussell

t o C ave

f or A sh C ave t runcate-margin s eeds

r anged f rom 1 1-21 m icrons.

Conclusions I n

a ddition

c ollections,

S EM

C ave c henopod d escription o f

t o

underscoring

a nalysis

o f

t he

t he

r esearch

l arge

u nmixed

potential R ussell

c ollections a llowed, f or t he f irst t he m icro-morphological s tructure o f

2 09

o f

C ave

museum a nd

A sh

t ime, a d etailed t he f ruits o f t he

Scanning electron micrograph of Russell Cave Chenopodium Fig. 1. seeds, showing the distinctive reticulative-alveolate dorsal pericarp pattern and the truncate margin seed configuration. From Smith, 1985a.

210

Fig. 2. Scanning electron micrographs showing outer seed coats in cross section: (top) Russell Cave seed (14 microns thick); (middle)�­ berlandieri ssp. nuttalliae cv 'chia' seed (20 microns thick); (bottom) �- berlandieri seed (41 microns thick). From Smith, 1985a.

211

t hin-testa c henopod c ultivar o f p rehistoric g arden s ystems o f t he E astern W oodlands. T his a ccurate d escription a nd m easurement o f e xtremely s mall f ruit s tructures ( e.g. p ericarp a nd e piderm p atterning a nd t hickness) a llowed r ather v ague d escriptive l abels s uch a s " thint esta" a nd " thick-testa" t o b e r eplaced b y s pecific n umerical v alues. I n a ddition, t he d etailed c omparison b etween t he R ussell C ave a nd A sh C ave s eed a ssemblages a nd m odern w ild a nd d omesticated f orms, p rovided, f or t he f irst t ime, a b asis f or t he c onfident a ssignment o f d omesticated s tatus a nd a f ormal t axonomic s ubspecies d esignation ( C. b erlandieri s sp. i onesianum ( Smith a nd F unk, 1 985) t hin-testa c henopod o f t he e astern U nited S tates. T his p otential

s pecific e xample t hat e xists f or

t o t he p rehistoric

s erves t o d emonstrate e xpanding a nd e nriching

t he s ignificant a rchaeobotanical

r esearch t hrough t he a pplication o f S EM t echnology. S EM m icrom orphological d escription a nd c omparative a nalysis o f a rchaeobotanical s eed a ssemblages s hould b ecome a r outine p rocedure, a nd b e a cknowledged a s a n ecessary p rerequisite t o a ny p roposed a ssignment o f d omesticated s tatus t o a rchaeobotanical p lant m aterials. S canning e lectron m icroscopy c learly h olds a n umber o f d istinctive a dvantages f or t he s tudy o f t he m icromorphology o f p rehistoric s eeds. O ften q uite d elicate, p articularly i f c arbonized, a rchaeobotanical s eed s pecimens s elected f or s tudy c an e asily b e m ounted t o S EM c over s lides u sing " Eimers" g lue. O nce m ounted a nd c oated, s uch d elicate s eed s pecimens c an b e r epeatedly s tudied i ntact t hrough a w ide r ange o f m agnification l evels a nd v iewing a ngles, a nd w ith g ood d epth o f f ield. P hotographic c apabilities a re p otentially e xcellent, w ith o n-line Polaroid a nd 4 x5 n egative f ormats a llowing e xtensive a nd e asy d ocumentation o f p reviously u nrecognized a nd p otentially i mportant m icromorphological c haracters. I ronically, h owever, i t i s o ften s till d ifficult, even i n l arge research u niversity s ettings, archaeologists a nd a rchaeobotanists t o t ake a dvantage o f

f or S EM

t echnology. M any t imes, s canning e lectron m icroscopes h ave e ither r estricted u se w ithin a p articular a cademic u nit, o r a re o perated o n a p aying c ustomer b asis, w hich m ay s eriously l imit t he a pplication o f t his v aluable u ser-friendly t echnology.

E nd N otes 1 .

A

s econd

c henopod

t axon

( Chenopodium

b ushianum)

i s

f requently

m entioned i n q uoted p assages. A lthough s till t echnically r ecognized a s d istinct s pecies, C . b erlandieri a nd C . b ushianum a re v ery c losely r elated. O nce d etailed g enetic r esearch o n p resent d ay s tands o f t hese t wo e astern N orth A merican t axons a re c arried o ut, C henopodium b ushianum i s b erlandieri.

l ikely

t o

b e

r elegated

2 12

t o

s ubspecific

s tatus

w ithin

C .

R eferences A sch,

D .

some

a nd A sch.

N .

prehistoric

1 977.

C henopod a s c ultigen:

collections

from

M idcontinental J ournal o f Archaeology 2 : A sch,

D .

a nd

p rehistoric

A sch,

N .

1 982.

h orticulture

Eastern

North

America .

3 -45.

A c hronology

i n W est-Central

t he 4 7th A nnual Meeting,

a r e-evaluation o f

f or

t he

I llinois.

d evelopment

o f

P aper presented a t

S ociety f or American Archaeology,

M inneapolis,

M innesota. A sch, M .B.

D .

a nd A sch,

( eds.),

A rchaeology, 1 37.

N .

1 983.

E xcavations

Archaeobotany.

a t

t he

S miling

I n S tafford,

Dan

C ontract A rchaeology P rogram,

S ite,

B .

C enter

a nd S ant,

f or American

R eport o f I nvestigations N o.

S ubmitted t o t he I llinois D epartment o f T ransportation.

A sch, D . T he H ill

a nd A sch, N . 1 985. A rchaeobotany. I n C onner, M .D. ( ed.), C reek H omestead, Kampsville Archaeological C enter R esearch

S eries

1 15-170.

A sch,

1 : N .

a nd A sch,

Woodland

D .

1 980.

A rchaeobotany

a nd P ond,

i n

T he

D ickson

I llinois.

I llinois S tate M useum,

G .

1 986a.

A rkansas

P rehistoric

R ockshelter

Camp a nd P ond S ites:

C antwell,

A .M.,

M iddle

D ickson

R eports o f I nvestigations 3 6:

d eWet, J .M.J. a nd H arlan, J .R. e volution i n t he man-made habitat. F ritz,

I n

C amp

1 52-160.

1 975. Weeds a nd d omesticates: E conomic Botany 2 9: 9 9-107.

O zark

C ollections.

Agriculture, U npublished

t he

P h.D.

U niversity

o f

d issertation,

U niversity o f N orth C arolina a t C hapel H ill. F ritz,

G .

1 986b.

S tarchy g rain

c rops

i n

t he

E astern

U nited

S tates:

E vidence f rom t he d esiccated O zark p lant r emains. P aper p resented a t t he 5 1st Annual M eeting o f t he S ociety f or American Archaeology, N ew O rleans, F ritz,

L ouisiana.

G .

a nd

d ocumenting

Smith,

t he

B .

1 988.

d omestication

O ld c ollections

o f

C henopodium

a nd

n ew

t echnology:

i n Eastern N orth America.

M idcontinental J ournal o f A rchaeology 1 3(1). H arlan,

J .R.,

d eWet,

e volution o f c ereals. J ones, W ebb,

V .

1 936.

W .S.

C ounty,

a nd

J .M.J.

a nd

P rice,

E volution 2 7:

E .G.

1 973.

C omparative

3 11-325.

T he v egetal r emains o f N ewt K ash H ollow S helter. F unkhouser,

K entucky.

U niversity

W .D. o f

( eds.), K entucky,

Rock

S helters

R eports

i n

I n

M enifee

i n Archaeology

a nd

A nthropology 3 (4) : 1 47-167. K orber-Grohne,

U .

T riticum

a nd

s canning

e lectron

1 981.

S ecale

o n

D istinguishing prehistoric t he basis

m icroscope.

o f

t heir

J ournal

1 97-204.

2 13

o f

c ereal

g rains

o f

s urface patterns

u sing

t he

Archaeological

S cience

8 :

Korber-Grohne, U. and Piening, U. 1980. Microstructure of the surfaces of carbonized and non-carbonized grains of cereals as observed in scanning electron and light microscopes as an additional aid in determining prehistoric findings. Flora 170: 189-228. Smith, B.D. 1984. Chenopodium as a prehistoric domesticate in Eastern North America: evidence from Russell Cave, Alabama. Science 226: 165167. Smith, B.D. 1985a. The role of Chenopodium as a domesticate in preSoutheastern maize garden systems of the Eastern United States. Archaeology 4: 51-72. Smith, B.D. 1985b. Chenopodium berlandieri ssp. jonesianum: evidence for a Hopewellian domesticate from Ash Cave, Ohio. Southeastern Archaeology 4: 107-133. Smith, B.D. and Funk, V.A. 1985. A newly described subfossil cultivar of Chenopodium (Chenopodiaceae). Phytologia 57: 445-448. 1981. Domesticated Chenopodiurn of the Ozark Bluff Wilson, H.D. dwellers. Economic Botany 35: 233-239. Yarnell, R.A. 1983. Prehistoric plant foods and husbandry in Eastern North America. Paper presented at the 48th Annual Meeting of the Society for American Archaeology, Pittsburgh, Pennsylvania.

214

THE SEM AND VICIEAE

SEED IDENTIFICATION, WITH PARTICULAR REFERENCE TO THE

E. Ann Butler Introduction to the Vicieae Legumes have been important economic resources since earliest times and are thought to have played a role similar to that of the cereals in the beginnings of agriculture (Renfrew, 1973). However, differential preservation acts against the seeds of legumes and charred material from these plants in early archaeological contexts is usually sparse in relation to the remains of cereals. Amongst the Leguminosae the Vicieae, a tribe represented by some 300 species, has contributed from its four main genera a number of well-known cultivars common throughout the Old World, including the pea, chickling pea, lentil and broad bean amongst many lesser known species. Identification by Optical Microscopy The identification of the remains of charred pulses has always been difficult. Commonly the material consists of fragments of the cotyledons which yield only estimations of the dimensions of the original seed as criteria by which to make the identification. Seed shape and size are known to be highly variable within species in the Vicieae, and such characters may even be unreliable indicators by which to separate genera (Gunn, 1970a). However, frequently some of the seedcoat remains, and even the hilum may be retained on the seed. The degree of rough- or smoothness of the testa, and the dimensions and shape of the hilum recorded under low magnifications have added to the criteria that have been employed for identification. The very limited depth of focus and poor resolution obtained by optical microscopy, even using epi-illumination, have severely restricted the observation of morphological detail, thereby making identifications tenuous. SEK Analysis The application of SEM to the study of seed surfaces has already shown rewarding results in archaeobotany, charred remains often showing very good preservation of morphology (Conolly, 1976). The recent work by Kislev and Hopf (1985) on the identification of Lathyrus sativus and L. cicera from the llth century BC site of Tell Qasile in Israel illustrates particularly the observations achievable by SEM on seeds of the Vicieae from antiquity.

• •

It is now ten years since Brisson and Peterson (1976) published a critical review of the use of SEM in the study of the seedcoat, and some of the points raised in that work are of particular relevance to archaeobotany. Of the several problems highlighted, a major cause for concern was the lack of consideration of the variation within species of the morphology and anatomy of the seedcoat; most frequently single 215

s pecimens o f a s pecies h ad b een e xamined a nd t he r ecords t hus d isplayed l ittle e vidence f or t he s tability o f t he c haracters d escribing t he d ifferent s pecies. T he n eed w as e xpressed f or m ore i llustrations o f s eeds u nder S EM t hat m ight b e u sed a s c omparatives a nd p rovide a k nowledge o f t he b readth o f t he r ange o f v ariation. A d ecade l ater, t he s ituation r emains l argely u nresolved . M any p ublications s till c ontain d ata r ecorded b y S EM f rom v ery f ew s pecimens p er s pecies a nd f ew s tudies h ave e xamined t he p otential r ange o f v ariation i n f eatures u nder i nvestigation. P art o f t he p roblem l ies i n t he d ifferent o bjectives f or t he u se o f S EM. W here t he p urpose i s t axonomic, b road t rends i n m orphology m ay b e s ought r ather t han t he r ange o f m orphological e xpression i n i ndividual c haracters. Y et f or t hose e ngaged i n t he i dentification a nd i nterpretation o f w hat m ay b e v ery s mall a mounts o f a ncient p lant m aterial, s ome a ppreciation o f t he p otential r ange o f v ariation i n i ndividual c haracters i s i mportant. T his v ariation i n s eed a natomy a nd n umber o f f actors, i ncluding d ifferences

m orphology m ay b e d ue t o a i n t he g enotype, p henotypic

p lasticity, t he s tate o f m aturity, p athologies a nd o ther c auses. T hat t he r esults o f t hese f actors h ave n ot b een a m ajor f ocus o f s tudy b y S EM m ay b e e xplained b y t he f act t hat t his t echnique d oes n ot r eadily l end i tself t o l arge s cale s urveys o f r eplicated m aterial. T he o peration o f t he i nstrument a nd n ecessarily a ssociated p hotography m ay b e t ime-consuming a nd l abour i ntensive; t he e quipment i s e xpensive t o b uy, m aintain a nd r un; a nd a ccess f or t he b orrowing o r h iring o f S EM f acilities i s t hus o ften v ery r estricted. F urthermore, r eference m aterial m ay b e i n s hort s upply s o t hat t he p reparation o f a l arge n umber o f S EM s amples m ay i nvolve t he p ermanent r emoval o f t oo m uch o f the reserve o f a s eed c ollection. I n t he c ase o f c harred a rchaeological m aterial, t he i rreversible r emoval o f p art o f a s ample h as t o b e v ery c arefully j ustified. G iven t he c onstraints d escribed a bove, a p artial s olution t o t he p roblem m ay l ie i n t he maximisation o f i nformation t hat m ay b e o btained f rom p ublications o f o ther a uthors i n o rder t o e xtend t he d atabase. T his r equires t he i nclusion o f f ull d etails o f m ethod, a ccurate r ecords o f t he n umbers o f o bservations, a nd d escriptions o f t he p opulations f rom w hich s pecimens h ave b een d rawn. S EM i s a t echnique t hat h as s ome g reat a dvantages i n t he e xamination o f s eeds. I n g eneral, r elatively l ittle p reparation o f t he s pecimen i s n ecessary p rior t o s canning. W here t he s eeds a re d ry, a s i s t he c ase i n m ature s eeds o f t he V icieae, f ixing a nd c ritical p oint d rying a re n ot r equired. C harred s eed m aterial i s p articularly s uitable f or s canning a nd m ay e ven b e s canned w ithout c oating ( Feindt a nd M esterharm, 1 980). T he d epth o f f ocus a llows f or g ood p hotographic r ecords o f s uch s ubjects a s s pherical s eeds a t m agnifications a s l ow a s x 12

o n

c ertain

i nstruments,

a nd

t he

h igh

r esolution

p rovides

d etailed o bservation o f a natomy a t m agnifications u p t o x 10,000 o paque c harred s eeds t hat c ould n ot b e s tudied b y o ther m eans.

2 16

f or o f

T he P resent S tudies I n

o rder

t o

e valuate

c haracters

t hat

may

b e

a pplied

t o

t he

i dentification a nd i nterpretation o f c harred material o f a rchaeological d erivation, o f

t he

a s tudy h as

s eedcoat

i n

b een u ndertaken

m embers

o f

t he

o f

t he morphology

V icieae.

F resh

a nd

s eeds

a natomy

h ave

b een

e xamined f rom 9 4 t axa, i ncluding 1 5 s pecies o f L athyrus, 5 s pecies o f L ens, a s c lassified b y L adizinsky ( 1986), 2 s ubspecies o f P isum a nd 1 4 s pecies o f V icia, b eing

s tudied

a n umber o f d ifferent p opulations o f t he s ame s pecies

w here

p ossible

( Table

1 ).

C harred material

f rom t hree

a rchaeological s ites h as a lso b een e xamined. T able 1 .

S pecies o f t he t ribe V icieae e xamined i n t he s tudy o f s eedcoat a natomy.

L athyrus a phaca

P isum s ativum e latius

nnuus L athyrus a

P isum s ativum s ativum a rvense

L athyrus c icera L athyrus c lymenum eterophyllus L athyrus h L athyrus h irsutus

V icia b ithynica

L athyrus i nconspicuus

V icia e rvilia

L athyrus

V icia f aba v ar m inor

V icia c racca

l axiflorus

L athyrus n iger

V icia f aba v ar paucijuga

L athyrus n issolia

V icia l utea

L athyrus o chrus

V icia m elanops

L athyrus pratensis

V icia n arbonensis

L athyrus s ativus

V icia n oeana

Lathyrus s ylvestris

V icia o robus

L athyrus t uberosus

V icia p eregrina V icia s ativa

ulinaris L ens c

V icia s ativa n igra

L ens o rientalis

V icia s epium

demensis L ens o

V icia s ylvatica

L ens n igricans

V icia t etrasperma

L ens e rvoides

Methods T he p rimary t echnique e mployed h as b een S EM, a t 1 2 a nd 2 5 k v, a nd a J EOL J SM 3 5 a t 1 5 k v,

5 00 o f

b etween x 12

a nd x 10,000.

u sing a P hilips P SEM u nder magnifications

S pecimens h ave b een c oated w ith g old by a

P olaron E 5000 s putter c oater t o a d epth o f 4 00-500A . S tubs h ilum S eeds

a nd a nd

t esta

i n

manner

prepared

s urface

o f

t he

mounted

t o

l ongitudinal

u nfixed,

S tirton t hey

c an

s tub.

A raldite, b een

b een

w ith

b oth

w hole

a djacent

s eeds

t o

t he

mounted

h ilum

t o

a nd

s how

a t

t he

m idseed.

h ave b een h alved by pressure f racture a t r ight a ngles a cross t he

h ilum

t o

h ave t esta

s how

t he

s ection

( pers.

h ilum

a round

c omm .).

t ake u p

i n

S ince

a tmospheric

C onsequently,

t he

t ransverse

s ection,

a nd

t he s eed c ircumference,

u se

t he

w ater o f

s eeds o r

a re

d ry o ut

h ard-setting

h ygroscopic a nd while a ttached g lues

s uch

o r c onducting paints s uch a s s ilver d ay f or t he a dhesive,

a voided,

d ifferential

d ue

t o

s tresses

t he

r isk

i mposed

b y

o f

l osing

t he

vacuum o f

2 17

t he

s pecimen

t he

t he

a fter t he

s putter

u nder

a s h as t he

c oater o r

t he S EM i tself. G enerally g lues d ry, s uch a s D urafix o r U HU, s atisfactory, s mall,

t hough

t hat r etain h ave b een

d ouble-sided

s ticky

a s light p lasticity w hen f ound t o b e t he most

t ape

h as

b een

e ffective

f or

l ight s eed f ragments o r c harred material.

T owards a g reater u nderstanding o f t he a natomy o f c ertain f eatures r evealed a cross

u nder

t he

s taining,

S EM,

h ilum

s ections

b een

o f

t he

o bserved

s eedcoat

u nder

c ut

l ight

t ransversely

m icroscopy

a fter

a s w ell a s b y S EM i n t hree s pecies o f L athyrus.

C haracters u nder

t hin

h ave

t raditionally

l ow magnifications

u sed

h ave b een

t o

i dentify

s eeds

r ecorded u nder

o f

l ight

t he

V icieae

m icroscopy

a t

m agnifications o f l ess t han x 50. O bservations t hose

o f

h ave

b een

o ther

a uthors.

a nd

a nalysed

e xpressed

q ualitatively

a ssessed

W here a ppropriate, b y

c luster

a nd

c ompared

w ith

d ata h ave b een n umerically

a nalyses

a nd

principal

c oordinate

a nalysis.

Results E xternal T esta S urface. s urface

i n

t he

P revious publications h ave d escribed t he t esta

V icieae

a s

c onsistently

papillose

( Lersten,

While u sually t his was f ound t o b e t he c ase i n t his s tudy, V icia

a nd

6

o f

L athyrus

e xemplified by L athyrus c onsistent o bserved

w ithin

w ithin

w ere

a phaca

e ach

s een

s pecies

d ifferent

w ith

( Plate b ut

1 ).

o ther

pattern

t ypes,

a s

T he g eneral pattern t ype i s

v ariations

populations

1 979).

2 s pecies o f

o f

t he

i n

d etail

s ame

h ave

s pecies

b een

t hat

a re

s ometimes g reater t han t hose o f d ifferent s pecies. S imilarly, s eeds f rom d ifferent g enera may e xhibit s trikingly s imilar t esta morphology, e xemplified b y V icia e rvilia a nd L athyrus s ativus I t

has

b een

c oncluded

t hat

( Figs.

t esta morphology

a lone

t o i dentify s pecies i n t he V icieae i n most c ases T esta p its t he

d escribed b y

L eguminosae

G unn,

1 982)

h ave

1 986)

a nd o ne

o f

a nd

a n umber o f

r eported

b een

i n

r ecorded h ere

V icia .

i n

o f

i n

s everal

o f

b e

u sed

i n press).

L athyrus

4 s pecies

3 ).

c annot

( Butler,

a uthors

3 s pecies

2 ,

g enera o f

( Lersten

L athyrus

a nd

( Butler,

T he pits a re o f o ccasional o ccurrence a nd a re

n ot a c onstant f eature w ithin s pecies o r e ven w ithin populations; t heir presence o r a bsence i s t herefore c onsidered t o b e u nstable a nd u nsuitable f or u se i n t he s eparation o f s pecies. T he o f

H ilum.

T he

c haracters

i dentify

s pecies

s eparation

e xternal

t hat

o f

m orphology

o f

t he

h ilum h as

y ielded a n umber

h ave b een u sed t raditionally a s a b asis b y w hich t o o f

w eedy

t he

V icieae,

s pecies

f rom

particularly c ultivars

w hen

( Gunn,

a pplied 1 970b).

t o

t he

I t

was

a nticipated t hat a s tudy o f t he i nternal a natomy o f t he h ilar r egion i n t ransverse t axonomists

s ection t hat

m ight

w hile

b e

focus

of

v alue.

I t

i s

c onsidered

by

s ome

s eed morphology may b e s ubject t o t he i nfluence

of environmental f actors, c onservative c haracteristics. useful

o f

p lant c ells a nd t issues h ave more V ascular t issue h as b een a particularly

i nterest

C onsequently, t he t racheid v ascular b undle ( Lersten,

bar, 1 982)

i n

t his

r espect

( Bell,

n o

d ate).

a s tructure d erived f rom t he ovule l ying b eneath t he h ilum, h as b een

2 18

F ig.

1 .

L athyrus a phaca.

F ig.

2 .

V icia e rvilia.

F ig.

3 .

L athyrus

T esta s urface,

T esta s urface,

s ativus.

n on-papillose t ype.

papillose t ype.

T esta s urface,

2 19

p apillose t ype.

c arefully e xamined i n t his s tudy. t ransverse p lane i n L athyrus c icera.

F igure

4

s hows

t he

h ilum

i n

T he t racheid b ar i s c omposed o f t racheoids, i ntercommunicating b y m eans o f p erforations s imilar t o t he p its f ound i n w ood e lements. T he s ize a nd s hape i n s ection o f t his t racheid b ar a ppear t o r emain r elatively c onstant w ithin s pecies, a nd t o b e c riteria t hat m ight p rove t o b e u seful f or i dentification. H owever, t he t racheoid p its h ave n ot c onformed t o t hose d escribed b y L ersten a nd G unn ( 1982) a s t ypical i n t he V icieae, a nd h ave n ot b een u niformly r egular, a nd n on-vestured. O nly o ne s pecies o f L athyrus, n o V icia a nd n ot a ll s pecies o f L ens h ad s mooth, p lain-bordered p its. A ll o ther t axa s howed a t l east s ome t racheoids w ith w arty o r e ven e laborately v estured p its ( Fig. 5 ). M ost c ommonly w ithin a s pecies a w ide r ange o f p it o rnamentation h as b een s een, a nd v ariations i n p it d istribution a nd s hape a nd a perture s hape h ave b een t he r ule. C learly a g reater u nderstanding o f t he i mplications b ehind t hese v ariable f eatures i s n ecessary b efore t hey c an b e i ncorporated i n d ata u sed f or t he s eparation o f s pecies. S erial s ections a long t he h ilum i n 3 s pecies o f L athyrus h ave b een s tudied, a nd n o c orrelation h as b een f ound b etween t ypes o f p itting a nd t he p osition o f p its r elative t o t he s ituation o f t he t racheoid e lements i n t he t racheid b ar. O bservations

i n

t he

s eedcoat o f m embers o f t he V icieae h ave s hown

e ven a t v ery h igh m agnifications t he b readth o f v ariation e ncountered during s tudies b y l ight m icroscopy u nder l ow m agnifications. I ndividual

c haracters

o f

m orphology

a nd

a natomy

u sually

c annot

b e

r eliably e mployed f or t he i dentification o f l egume s eeds. T hus c luster a nalysis a nd p rincipal c oordinates a nalysis h ave b een a pplied t o a n a rray o f c riteria t o s eek s eparation o f s pecies. M ultivariate A nalysis. T he r esults o f a p ilot s tudy o f 1 3 s pecies o f L athyrus u sing 1 1 c haracters o f t he e xternal t esta m orphology a nd h ilum i n t ransverse s ection, h ave s hown t hat s ome t axonomically s ignificant s eparations c an b e a chieved, a nd t hat u seful c haracters c an b e f ound i n t he w idth a nd d epth o f t he h ilum a nd a ssociated t racheid b ar ( Butler, 1 986). C urrently, a nalyses a re i n p rogress o f 6 0 p opulations o f L athyrus a nd V icia u sing 4 7 c haracters. P reliminary r esults i ndicate t hat, w hile i ntrageneric s eparations c an b e a chieved, t hose b etween g enera a re m ore d ifficult. T his i s i n a greement w ith t he w ork o f L ersten a nd G unn ( 1982), u sing t raditional c riteria v isible u nder l ow p ower m icroscopy. S cattergrams o f t he e igen v alues o f a xes I a nd I I s how o verlap o f g roupings o f s pecies f rom b oth g enera. A gain, h owever, t he p arameters r elating t o t he d epth a nd w idth o f t he h ilum a nd t racheid b ar a re r esponsible f or m ost o f t he s eparations ( Butler, i n p ress). F urther a nalyses w ill b e n ecessary b efore d efinite c onclusions c an b e d rawn, a nd t hese r esults t ogether w ith f ull d ata w ill b e t he s ubject o f a f uture p ublication.

A pplications t o Archaeobotany M aterial f rom t hree a rchaeological s ites h as b een e xamined b y S EM, i n o rder t o e stablish t he r elevance o f t he s tudy o f f resh m aterial t o

2 20

Fig.

4 ,

L athyrus c icera.

Fig.

5 .

V icia f aba.

T S h ilum .

T racheoid pits o f mixed t ype.

2 21

a rchaeobotany.

C harred

Manerba,

f rom t he

f rom

I taly,

G ordion,

T urkey,

l egume

s eeds

f rom s ites a t T ell B rak,

B ronze A ge

o f

7 th

a nd

c entury

C halcolithic

B C

d ate

h ave

I raq a nd

r espectively

r etained

a nd

l ittle

o f

t he t esta. I n a ddition, v ery f ew h ave h ad t he h ila preserved i n s itu. H owever, c areful s orting o f f ractions r etained i n s mall mesh s ieves h as s hown

t hat

d etached

s eparated.

T hese

f ragments

v ery

s mall

o f

t esta

r emains

b earing

o ften

t he

s how

h ilum

u nder

c an

S EM

b e

c lear

patterning o f t he t opography o f t he e xterior s urface o f t he t esta, a nd when pressure-fractured a cross t he h ilum r eveal w ell-preserved a natomical c haracters t hat w ould permit r ecords o f t he s ame c riteria t hat

h ave

t hese

b een

c ollected

d etached h ila

f or

i n

S EM

f resh material s tudy,

allow for the conservation a rchaeobotanical s ample, a nd t hus

r ather

( Figs. t han

6 ,

t he

7 ).

w hole

T he

u se

s eeds,

o f

w ould

o f t he major s pecimens i n r emove a n i mportant obstacle t o

t he t he

a pplication o f t he S EM i n a rchaeobotany.

Conclusions T he

n eed

f or

a g reater

u nderstanding

o f

t he

a natomical

f eatures

r evealed b y S EM o f p lant s urfaces h as b een e xpressed by H eywood ( 1985). D uring t his project i t h as b een f ound t hat while S EM t ogether w ith l ight m icroscopy

c an

c ontribute

t owards

c haracters o f a natomy a nd m orphology, o f

a n umber

o f

f eatures

t hat

have

c ollection o f

a n

a rray o f

been

i nclusion

r emain

t hat

may

V icieae.

E stablishment o f t he s tability o f c haracters employed i n s eed

t he

t heir

r ecorded

d atabase

f or

f or

a nd

understood

u sed

a llow

o bserved

i nsufficiently

b e

t o

t he

t he v ariation i n a nd s ignificance

i dentification

o f

w ithin

s eeds

t he

o f

t he

i dentification i s i mportant. T he

a pplication

c riteria basis

o f

f rom f eatures

f or

more

t he

o f

c ertain

t he

S EM

t o

t he

c ollection

o f

a n

a rray

s eedcoat

o f

f resh material may

i nterpretations

o f

a rchaeobotanical

o f

f orm t he

s amples

o f

s eeds o f t he V icieae.

Acknowledgements S eed

s amples

h ave

b een

k indly

s upplied

by

M r.

G .C.

H illman,

I nstitute o f Archaeology, L ondon; by D r. F .A . B isby, Taxonomic U nit, B iology D epartment, U niversity o f S outhampton; P rofessor G . L adizinsky, t he

H ebrew

I nstitute

U niversity

o f

available

P lant

a t

t he

Crystallography u npublished

o f

J erusalem;

I ndustry, B iology

D epartment,

program

f or

a nd

L eningrad.

t he

D epartment, B irkbeck

c luster

N .I.

Vavilov

A ll-Union

S EM f acilities have b een made I mperial C ollege

a nalysis

C ollege

L ondon.

w ritten

by

a nd

t he

U sing

P rofessor

a n R .G.

D avis a nd h is own p rogram f or principal c oordinate a nalysis, t he m ultivariate a nalyses w ere c arried o ut by D r. D .H. D alby o f I mperial C ollege

L ondon,

c harred

s eed material w as

M .

C harles

o f

Archaeology

whose

( Tell

B rak)

L ondon.

h elp

i s

g ratefully a cknowledged.

s upplied by Mr.

a nd M iss S . T he

G .C .

C olledge

a dvice

o f

D r.

( Manerba) C .

Archaeological

H illman

( Gordion),

S tirton,

G ardens, K ew, h as b een m uch a ppreciated. T he work was g rant f rom t he S cience a nd E ngineering R esearch C ouncil.

2 22

Mr.

o f t he I nstitute Royal

B otanic

f unded

by

a

F ig.

6 .

P isum

c f.

M anerba,

I taly.

Fig.

P isum s p.

7 .

s ativum

a rvense.

C harred

t esta

s urface,

f rom

C halcolithic s ite.

C harred T S h ilum,

s ite.

2 23

f rom T ell B rak,

I raq.

B ronze a ge

R eferences B risson, o f

t he

J .D.

a nd

P eterson,

s canning

e lectron

R .L.

1 976.

m icroscope

A c ritical

r eview o f t he u se

t he

o f

i n

s tudy

t he

s eedcoat.

S canning E lectron M icroscopy P art V II/1976. B utler,

E .A .

1 986.

A .K . a nd C ombes, 1 985, pp. 2 5-38. B utler, E .A . P roceedings o f

C .R.

i n

t he

s eedcoat

I n press. T he V icieae: t he 7 th S ymposium o f t he

P alaeoethnobotany. B ell,

S tudies

N o

o f

L athyrus.

I n

K aul,

D . ( eds.) P roceedings o f t he C olloque L athyrus, P au N ew Y ork : T hird W orld M edical R esearch F oundation. problems i n i dentification. I nternational W ork G roup f or

C ambridge 1 986.

d ate.

P lant

v ariation

a nd

c lassification.

L ondon:

M acmillan a nd C o. C onolly,

A .

1 976.

i dentification P apaver. F eindt,

T he u se o f t he s canning e lectron m icroscope f or t he

o f

s eeds,

F .

a nd M esterharm ,

P alaoethnobotanik. H amburg, G unn,

1 7:

1 970a.

A k ey

C .R.

A nalysts 6 0:

S eeds

I nstitut

a nd

d iagram f or o f

o f

1 985.

t he

t ribe o f

S canning

r ecognition

M .E.

a nd

a nd

G .

H opf,

1 986.

N .R.

1 979.

( Papilionoidae:

L ersten,

A llgemeine

B otanik,

S eed

T esting

V icieae

( Leguminosae)

i n N orth

t he A ssociation o f O fficial S eed

e lectron

microscopy:

P roceedings

p erception,

o f

t he

R oyal

2 2-23.

M .

1 985.

F ood

r emains

f rom T ell

Q edem 2 0:

A n ew L ens f rom t he M iddle E ast.

N otes f rom t he

4 89-492.

A d istinctive

L eguminosae).

Q asile w ith

1 40-147.

s eed

c oat pattern

P roceedings

o f

t he

i n

t he V icieae

I owa

A cademy

o f

1 02-104.

N .R.

( Leguminosae:

1 982.

T racheid bar

P apilionoidae).

L ersten,

N .R .

V icieae,

w ith

( Fabaceae).

f ür

I nternational

s ystematics.

R oyal B otanic Garden Edinburgh 4 3:

S cience 8 6:

a nd

t he s eeds o f 1 00 s pecies o f

t he

s pecial r eference t o L athyrus s ativus/cicera.

L ersten,

S axifraga

4 8-70.

V .H.

L adizinsky,

t o

R asterelekronenmikroskopie i n d er

d er

P roceedings

M icroscopical S ociety 2 0: K islev,

r eference

7 73-790.

1 970b.

c haracter

1 980.

P roceedings

American A griculture.

H eywood,

G .

M itteilung

( Leguminosae).

A ssociation 3 5: G unn,

s pecial 2 9-32.

1 35-143.

C .R .

V icia

w ith

F olia Q uaternaria 4 7:

a nd

G unn,

n otes

C .R.

a bout

a nd

1 982. t ribes

T esta Abreae,

U SDA T echnical B ulletin N o.

R enfrew, J .M. P ress, p . 1 04.

1 973.

v estured p its

i n

l egume

American J ournal o f B otany 6 9:

P alaeoethnobotany.

2 24

c haracters C icereae

i n

a nd

s eeds

9 8-107. t he

t ribe

T rifolieae

1 667. N ew York:

C olumbia U niversity

S CANNING E LECTRON S TUDIES O F T HE C ELL P ATTERNS O F T HE P ERICARP LAYERS OF S OME W ILD W HEATS AND R YES. M ETHODS AND P ROBLEMS S usan C olledge I ntroduction

o f

T he w ork o utlined i n t his p aper w as c arried o ut d uring t he p eriod f unding o f t he S cience a nd E ngineering R esearch C ouncil s ponsored

p roject n umber G R/B/80796, " Early M anipulations o f P lant R esources i n N ear E astern S teppe a nd R iverine F orest" ( hereafter r eferred t o a s " The A bu H ureyra P roject"). T he p roject w as i nitiated a nd d irected b y M r. G ordon H illman a nd P rofessor D avid H arris a t t he I nstitute o f A rchaeology, L ondon. T he h igh p owered m agnification w hich c an b e a chieved w ith s canning e lectron m icroscopy w as r equired f or t his s tudy t o f acilitate t he i nvestigation o f t he m icrostructure o f t he o uter c ell l ayers o f c ereal a nd g rass s eeds. F igure 1 s hows t he c omposition o f t hese l ayers. I n t he f amily G ramineae ( which i ncludes g rasses a nd c ereals) t he p ericarp ( fruit w all) a nd t esta ( seed c oat) a re f used t ogether t o f orm t he c overing l ayers o f t he s eeds. O f p articular i nterest i n t his i nvestigation a re t he l ongitudinal, t ransverse a nd t ube c ell l ayers. F igure 2 g ives t he c onfiguration o f t hese l ayers o n a g rain o f w heat. I mportant p ioneer w ork c arried o ut b y P rofessor K orber-Grohne ( Korber-Grohne a nd P iening 1 980; K orber-Grohne 1 981) p rovided t he b asis f or t his s tudy. S he r ealised t he p otential o f u sing m orphological details o f t he m icrostructure o f t he s eed p ericarp l ayers i n i dentification o f c ereal s pecies. H er w ork w as a d irect r esponse t o o ne o f t he g reatest p roblems i n a rchaeobotany: t he i dentification o f a ncient c ereal g rains w here t he g ross m orphological c haracteristics o f t he s eeds a re n ot n ecessarily d iagnostic. T he v erification o f s pecies o f w ild a nd d omestic c ereals f ound w ithin a rchaeological d eposits, f rom a ll p eriods, i s v ital i n o rder t o u nderstand t he d evelopment, a nd s pread o f t he v arious r aces o f c rop p lants. A s p art o f i dentified g rains

e mergence

h er i nvestigation K orber-Grohne p repared m odern, o f w heat, b arley a nd r ye s pecies a nd u sed a s canning

e lectron m icroscope, a t magnifications o f b etween 2 00 a nd 2 ,000 t imes, t o s urvey t he l ayers o f t he p ericarp. M uch o f h er w ork w as c oncentrated o n i nvestigation o f t he t ransverse c ell l ayers. I t w as n ecessary t o q uantify c ertain m orphological f eatures t o a llow f or a n o bjective a ssessment o f t he c ell p atterns. K orber-Grohne i ncluded t he l ength a nd b readth m easurements o f t he c ells ( both a bsolute a nd r elative), t he t hickness o f t he c ell w alls, t he a mount o f p itting i n t he c ell w alls a nd t he o verall s hape a nd a rrangement o f t he c ells i n t he t ransverse l ayer. T o c omplete t he c haracterisation o f t he p atterns s he a lso n oted t he n umber o f c ell l ayers w ithin t he l ongitudinal l ayer a nd t he p resence o f t he t ube c ells. K orber-Grohne f ound a c onstancy o f t hese f eatures w ithin s pecies, s uch t hat, o n t he b asis o f c omparison o f t hese q uantitative p arameters f or m odern s pecimens, s he w as a ble t o s uggest t he p ossibility o f d ifferentiation b etween w ild a ncestral f orms a nd t heir e quivalent d omesticated s pecies. S he w as, h owever, c areful t o s tress t he i nadequacy o f s cientific t esting i n h er w ork. T he d iagnosis o f m orphological f eatures i n t he p ericarp l ayers w as a pplied

2 25

o u te r e p ide rm is h ypode rm is

O

0 =3

• = G

= ..

=

0

;

0 (---

C =2 0 p == = >C== 4 =

p ar en chyma i n ner e p ide rm is

0

p e r ica rp

L o ng i tud ina l c e l l s t ransverse c e l ls \ t ub e c e l ls \s e ed c oa t/tes ta n u c e l la r l a ye r a l eu rone

C

s ta r ch

C )

S ec t ion t h rough t h e o u te r l a ye rs o f a w hea t g ra in .

F ig.

1 .

D iagrammatic

r epresentation

w heat g rain.

2 26

o f

t he

o uter

c ell

l ayers

o f

a

A pex

L o ng i tud ina l c e l ls t r ans ve rs e c e l ls t ube c e l ls V en t ra l s u r fa ce

D orsa l s ur fa ce E mbryo

F ig. 2 . D iagrammatic r epresentation o f t he l ateral s urface o f a w heat g rain s howing t he c onfiguration o f l ongitudinal, t ransverse a nd t ube c ell l ayers.

2 27

t o

S EM p hotomicrographs

o f

a ncient

c harred g rains

a nd,

b y c omparison,

i dentifications w ere m ade. T his w as t he s tate o f k nowledge a t t he t ime o f t he A bu H ureyra P roject. A rchaeobotanists w ere b eginning t o u se t he d iagnostic c riteria i n t he i dentification o f a ncient c ereal g rains f rom a rchaeological s ites o f v aried d istribution, b oth g eographically a nd c hronologically, a nd t heir i nterpretations w ere m ade a ccordingly.

T he Abu H ureyra P roject T ell A bu H ureyra i s a s ite i n n orthern S yria o n t he s outhern b ank o f t he R iver E uphrates. O ccupation a t t he s ite e xtended f rom E pipalaeolithic t hrough t o A ceramic a nd C eramic N eolithic p eriods ( c. 9 000 b c t o 6 000 b c). T he s ite w as e xcavated d uring t wo s easons i n 1 972 a nd 1 973 ( Moore, e t a l. 1 975). T he i nitial r ecovery o f t he a ncient, c harred p lant r emains f rom w ithin t he o ccupation d eposits a nd t he s ubsequent a rchaeobotanical r esearch, c arried o ut d uring t he t hree y ear f unding o f t he p roject, w ere u ndertaken w ith t he a im o f a nswering v ery s pecific q uestions r elating t o t he b eginnings o f c ultivation a nd e mergence o f f ully d omestic c rops i n t hat a rea o f t he N ear E ast. p reservation o f t he c harred p lant m aterial f rom E pipalaeolithic N eolithic l evels w ithin t he t ell w as e xcellent. H illman r ecognised

t he T he a nd t he

p otential f or i nvestigation o f t he t ransition f rom g athering w ild p lant f oods t o t he f irst s tages o f a griculture w ith m anaged c rops. H e w anted, i n p articular, t o t race a ny s igns o f e arly m anipulation o f w ild p lant f oods i n t he E pipalaeolithic p eriod a nd, t hus, t o a ttempt t o d efine t he c ircumstances a nd p rocesses w hich g ave r ise t o f ully d omesticated c ereal s pecies i n t he N eolithic. H illman ( pers. c omm .) c onsidered t here w as a p ossibility t hat h istological c hanges i n t he s eed ( i.e. c hanges i n t he m icrostructure o f t he c ells o f t he p ericarp l ayers) m ight h ave o ccurred p rior t o a ny g ross m orphological c hanges i n r achis s tructure a nd g rain s hape o nce t he w ild p lants w ere u nder m an's i nfluence. D omestic c ereals h ave a t ough r achis w hich d oes n ot s hatter w hen s eed

t he e ar i s m ature, i n w ild s pecies t he r achis i s ' brittle' a nd d ispersal o ccurs a utomatically a t m aturity . A lteration o f g rain

s hape a nd s ize a ccompanies d omestication o f t he s pecies. T he r esearch w as d esigned t o l ook f or t hese h istological c hanges u sing t he s canning e lectron m icroscope o n g rains o f w ild e inkorn, T riticum b oeoticum, a nd w ild r yes, S ecale s pp., f rom E pipalaeolithic o ccupation d eposits a t A bu H ureyra ( Figs. 3 c, d ). I f t hese c hanges c ould

b e

i solated

i t

w as

o bvious

t hat

t he

i mplications

w ould b e f ar

r eaching.

S EM S tudies o f Modern G rains P rior t o t he e xamination o f t he a ncient g rains i t w as n ecessary t o u ndertake a t horough s urvey o f m odern s pecimens o f t he e quivalent s pecies. T able 1 l ists t he s pecies w hich w ere u sed a nd t he h abitats w here t hey w ere c ollected. F or t he w ild c ereal s pecies t he p rimary h abitats r efer t o t he n atural w ild s tands a nd t he s egetal h abitats r efer t o w hen t he p lants w ere f ound g rowing i n a f ield o f c rops. T he l atter f orms m ight w ell m imic t he s ituation o f t he E pipalaeolithic

2 28

T ABLE

1 :

M odern

P opulations

o f

Wheats

a nd

R yes

u sed

i n

t he

S EM

R eference S tudy* 1 .

T riticum b oeoticum : A .

1 . 2 .

C .

- 1 _ tl

a nd 2 ' s pikelets I

I

I

T urkey, T urkey,

G CH 1 8176 D HF 4 20

- l ' a nd 2 ' s pikelets _ I t I t

6 . 7 . 8 .

T urkey, T urkey, T urkey,

G CH 3 070 G CH 2 264 G CH 3 705

_ e t _ t e _It

e t t

T urkey, T urkey,

GCH 3 341 P BI

T riticum boeoticum var.

I t

I t

I

D erived f rom i ntermediate habitats

A .

I t

( disturbed,

but u ncultivated)

- l ' a nd 2 ' s pikelets / I

u rartu:

I t

I t

t I

s ingle-toothed w ild e inkorn

D erived f rom p rimary habitats 1 1. T urkey, I CARDA 5 5130 - l ' a nd 2 ' s pikelets 1 2. S yria, I CARDA 2 0049 _ t e I I 1 3. 1 4.

B .

S yria, S yria,

I CARDA 2 0033 I CARDA 2 0125

I t I t

V t

f t

I t

I t

I t

D erived f rom s egetal habitats 1 5. S yria, I CARDA 2 0186 - 2 ' s pikelets o nly

T riticum monococcum : A .

4 .

G CH 3 091 G CH 3 771

habitats

4 . 5 .

9 . 1 0.

3 .

T urkey, T urkey,

( wild)

3 . T urkey, G CH 3 219 - 1 ' s pikelets o nly D erived f rom s egetal habitats ( i.e. g rowing a s w eeds o f c rops)

B .

2 .

w ild-type e inkorn

D erived f rom p rimary

f ully d omesticated e inkorn

G rown a s c rops 1 6.

T urkey,

P BI

1 7.

T urkey,

Z ohary

1 8.

T urkey,

J BB

S ecale

-

s pikelets o nly

-

montanum :

w ild

V I

mountain

r ye

( all

r ye

s pikelets

a re

2

g rained) A . D erived f rom p rimary habitats

5 .

1 9. 2 0.

T urkey, T urkey,

G CH 3 094 G CH 3 215

2 1.

T urkey,

G CH 2 618

S ecale s ylvestre: A .

v ia URBG

U SSR,

C rete,

van Z eist

S ecale c ereale:

c ultivated r ye

D erived f rom s egetal habitats 2 5.

B .

- 2 ' s pikelets

h airy w ild r ye

D erived f rom p rimary habitats 2 4.

A .

- 2 ' s pikelets

v ia UMBG

H aynaldia v illosa : A .

7 .

U SSR,

D erived f rom s egetal habitats 2 3.

6 .

w ild s and r ye

D erived f rom primary habitats 2 2.

B .

- 2 ' s pikelets _ I I t

T urkey,

G CH 1 8186

( subsp. - 2 '

A c ultivated c rop i n i ts o wn r ight 2 6. 2 7.

T urkey, T urkey,

G CH 2 921a G CH 3 544a

2 8.

U nited K ingdom,

2 9.

T urkey,

s egetale)

s pikelets ( subsp.

c ereale)

- 2 ' s pikelets _ e t

P BI

_ i t

G CH 2 872b

* 1 ' r efers t o t he g rain f rom a o ne-grained s pikelet, 2 'S r efers t o t he s maller o f t he t wo g rains f rom a t wo-grained s pikelet, a nd 2 'L r efers t o t he l arger o f t he t wo g rains f rom a t wo-grained s pikelet.

2 29

Fig.

3 .

a .

T riticum

u rartu

2 'L

o verlying t ransverse c ell l ayer, t ube

c ells

s pecimens

r unning f rom

u nder

t he

Epipalaeolithic

L evel n umber E 2 81,

d .

( SY b .

2 0125):

l ongitudinal

T riticum monococcum 1

t ransverse l evels

a t

L evel n umber E 3 26.

2 30

c ell T ell

l ayer.

c ell ( D.

c .,

Abu H ureyra,

l ayer

Z ohary):

d .

Ancient

S yria:

c .

m anipulation o f w ild g rasses a nd c ereals. T he f irst s tage o f t he r esearch w as, t herefore, t o d etermine w hether t here w ere d ifferences i n t he t ransverse c ell p atterns b etween g rains o f t he s ame s pecies f rom p rimary a nd s egetal p opulations ( Fig. 4 ). T able 2 l ists t he f eatures a nd m easurements c omparison.

o f

t he

c ell

p atterns

w hich

w ere

c onsidered

f or

M ethods T he m odern g rains w ere s oaked i n w ater f or 1 -2 h ours t o f acilitate t he r emoval o f c ell l ayers a bove t he t ransverse c ells. A p robe w as u sed t o s ecure t he g rain o n i ts s ide a nd w ith f ine f orceps i t w as p ossible t o p eel o ff t he l ayers b y g ently p ulling a t t he h airs a t t he a pical e nd. U sually t he l ayers o n t he t wo l ateral s urfaces c ame a way w ithout t earing. T he g rains w ere t hen p ut i n a n o ven f or a bout 1 6 h ours a t a t emperature o f 2 30 ' "C t o r eplicate t he c harring o f t he a ncient r emains. A ll s pecimens w ere d rawn b efore a nd a fter c harring, t o t ake a ccount o f a ny s ize c hanges w hich m ight a ffect t he c ell p atterns. N o o ther p reparation w as r equired a nd t he g rains w ere m ounted o n t he S EM s tubs w ith d ouble s ided s ticky t ape o n t heir l ateral s urfaces a nd w ere s putter c oated w ith g old t o a t hickness o f c . 4 0 n m . I n h er i nvestigations K orber-Grohne d escribed a n a rea o n t he c ereal g rains w hich s howed l east d istortion o f t ransverse c ells, a nd s he b ased a ll h er q uantitative a nalysis o n t he p atterns i n t his a rea. F or t his s tudy t he a rea o f t he g rain w as d ivided i nto t hree s ections ( Figure 5 )

a nd e ach p art w as s canned s eparately .

R esults I t m ust b e

s tressed

t hat

t he

i nvestigation

i s

f ar

f rom c omplete.

A s y et, n o d etailed q uantitative a nalyses h ave b een a pplied t o t he S EM p hotomicrographs. T he r esults g iven h ere a re, t herefore, p reliminary. T he e xpected.

s tudy

h ighlighted

m any

m ore

p roblems

t han

w ere

i nitially

T he r esearch i ndicated t hat:

i )

t here w as n o c onstancy o f c ell p atterns o f t he t ransverse l ayer o n o ne g rain ( Figs. 6 a-c);

i i)

t here w as n o c onstancy o f c ell p atterns o f t he t ransverse l ayer o n g rains f rom a o ne-grained s pikelet a nd a t wo-grained s pikelet o f t he s ame e ar ( Figs. 6 d-f);

i ii)

t here w as n o c onstancy o f c ell p atterns o f t he t ransverse l ayer o n g rains o f t he s ame s pecies f rom d ifferent p opulations ( Figs. 7 a, b ); t here w ere, h owever, s triking s imilarities o f c ell p atterns o f t he t ransverse l ayer o n g rains o f w ild a ncestral f orms o f w heat a nd r ye a nd o n t heir e quivalent d omesticated s pecies ( Figs. 7 c, d ); a nd t here w ere s imilarities o f c ell p atterns o f t he t ransverse l ayer o n g rains o f d ifferent g enera ( Figs 7 e, f ).

i v)

v )

F rom t his s tudy i t i s o bvious t hat t he u se o f m icromorphological f eatures o f t he p ericarp l ayers o f c ereals c annot b e a pplied i n s uch

2 31

T ABLE 2 : C riteria E xamined P ericarp o n M odern C ereals

i n

t he

C ell

P atterns

o f

L ayers

o f

L ongitudinal C ells * :

n umber o f l ayers c ell s hape c ell s ize w all t hickness v isibility o f p itting

T ransverse C ells:

n umber o f l ayers c ell l ength c ell w idth l ength/width r atio p resence o f i ntercalated c ells s hape o f i ntercalated c ells e nd w all c urvature e nd w all t hickening e nd w all o verlap w ith a djacent r ows o f c ells s ide w all t hickening s ide w all p itting: p rominence :d istribution, r egularity o ccurrence o f a ngular l acunae a t c ell e nds

T ube C ells:

p resence d istribution o ver t he w hole g rain r egularity, d ensity w idth o f t ubes t hickness o f t ube w alls

e xamined u nder o ptical l ight m icroscope o nly

2 32

t he

c e l l t e nth e nd w a l l o ver lap

c e l l b r ead th i n t er ca la t ed 4 - c e l ls e nd w a l l t h icken ing p i t t ing a ngu lar l a cunae

T r ansverse c e l ls

F ig. 5 . D iagrammatic r epresentation o f t he l ateral g rain s howing t he d ivision i nto a reas f or s canning.

F ig.

4 .

D iagrammatic

r epresentation

o f

t he

v iew

t ransverse

o f

a w heat

c ell

l ayer,

s howing t he f eatures u sed f or t he c omparison o f t he c ell p atterns.

2 33

a

F ig.

6 .

a -c.

T riticum m onococcum

( PBI,

c ):

d ifferent c ell

p atterns i n d ifferent a reas o f t he s ame g rain, a . a pex, b . m iddle, b ottom . d -f. T riticum m onococcum ( D. Z ohary): d ifferences i n c ell p atterns o n g rains f rom o ne-grained s ame e ar: d . 2 'S, e . 2 'L, f . 1.

2 34

a nd

t wo-grained

s pikelets

o f

c . t he

F ig. 7 . a , b . g rains o f t he b .

( PBI).

S ecale c ereale: d ifferences i n t he c ell patterns o n t he s ame s pecies f rom d ifferent populations: a . ( GCH 2 921a), c ,

d .

d ifferent s pecies: 2 'L

( D.

Z ohary).

S imilarities c . e ,

d ifferent g enera: e . c ereale, ( GCH 3 094).

o f

t he

T riticum b oeoticum, f .

c ell 2 'L

patterns ( PBI),

d .

o n T .

g rains

o f

monococcum,

S imilarities o f t he c ell patterns o n g rains o f

T riticum

monococcum'

2 35

2 'S

( D.

Z ohary),

f .

S ecale

K orber-Grohne

h erself

b een

c ritical

a m uch more

a nalyses

t horough

i nvestigation o f

a r ange

T he

t emptation,

i n

past,

t o

m icroscopy s pecies

i n

t he

u ntil, t he

f inal

r epresented

h ighlighted

t he

a rchaeological

a s

h as

c onfirmation

i n

t he

a ncient

l imitations s pecimens

u se

both

a lso

t here

h as

modern s pecies.

s canning

e lectron

o f t he i dentification o f t he c rop r emains.

i mposed

a nd

b een

a dmits, o f

b y

T his

by

t he

t he

i nvestigation

preservation

l ack

o f

o f

h as t he

c haracterisation

a mongst t he m odern s pecies.

R eferences K orber-Grohne, U . a nd P iening, U . 1 980. M icrostructure o f t he s urfaces o f c arbonised a nd n on-carbonised g rains o f c ereals a s o bserved l ight

m icroscopes

d etermining p rehistoric f indings.

i n

s canning

e lectron

F lora 1 70:

K orber-Grohne,

U .

T riticum

a nd

s canning

e lectron

a nd

1 981.

S ecale

o n

a s

a n

a dditional

D istinguishing prehistoric t he

basis

m icroscope.

o f

t heir

J ournal

o f

a id

i n

1 89-228. c ereal

g rains

o f

s urface patterns

u sing

t he

Archaeological

S cience

8 :

H ureyra

i n

1 97-204. M oore,

A .M.T.

a l.

1 975.

S yria:

a p reliminary

r eport.

4 1:

e t

T he

e xcavation

P roceedings

5 0-77.

2 36

o f

o f t he

T ell

Abu

P rehistoric

S ociety

P ART V I :

AN IMAL MATER IALS

2 37

T HE D ETECTION OF D IAGENETIC C HANGES I N N ON-MARINE S HELLS P RIOR T O T HEIR S UBMISSION F OR 1 4 1 C D ATING T im Yates

Abstract T he u se o f s hells f rom t errestrial a nd f reshwater m olluscs f or '4 C d ating h as i n t he p ast b een v iewed w ith s kepticism b ecause t he r esults a re p rone t o d istortion f rom p ost-depositional d iagenesis, o r t he i ncorporation o f m aterial w ith a l ow 1 4 C /1 2 C r atio w hilst t he m ollusc w as a live, o r b oth. T his paper d eals w ith t hree a spects o f a l arger p roject: d iagenetic c hanges, t heir d etection a nd t heir e ffect o n d ating. D iagenesis w as s tudied b y c omparing t he s tructure a nd c hemical c omposition o f m odern s pecimens w ith t hose o f f ossil s amples. S canning e lectron m icroscopy s howed t hat f ive s tructures w ere p resent i n f reshwater s hells a nd o ne i n t errestrial s hells; t hree f orms o f p ostd epositional s tructural c hange w ere o bserved. T he e ffect o f d iagenetic a lteration o n ' 'C d ates i s c onsidered u sing d ates o btained o n f ossil s amples u sing A ccelerator M ass S pectrometry ( ANS) t echniques.

I ntroduction The chronology o f d evelopmental p rocesses i n e nvironment, l andscape o r s ociety o ften c alls f or '4 C d ating o f s ome f orm o f c alcium c arbonate, s uch a s s hells, c arbonate n odules, c alcite o r t ufa. W here p reservation c onditions a re s uitable t hese m aterials m ay b e a vailable i n q uantities t hat a llow c onventional 1 4 C d ating ( Evin e t a l., 1 980; T horpe, O tlet a nd S weeting, 1 980; C allen, W asson a nd G illespie, 1 983), a nd w ill c ertainly b e a vailable i n t he q uantities r equired f or A NS t echniques; t hey a re, h owever, o ften u sed o nly a s a l ast r esort b ecause t he a ges t hey y ield a re c onsidered u nreliable f or a ccurate d ating. E arlier s tudies o n marine m olluscs ( Gillespie a nd P olach, 1 979; M angerud, 1 972) h ave s uggested t hat t he a ssociated e rrors m ay b e q uantifiable w ithin s tatistical l imits, a nd t he w ork o f V ita-Finzi ( 1980; V ita-Finzi a nd R oberts, 1 984) h as e mphasized t he i mportance o f s ample p reparation i n o btaining r eliable r esults. O lsson, G öksu a nd S tenberg ( 1968) h ave a lso e mphasized t he r isk f or c ontamination b y a dsorption o f C O, b y s toring i n t he a tmosphere. L and a nd f reshwater m olluscan s hells a re e ven m ore s uspect t han m arine s hells s ince t hey c ontain m aterial w hich m ay h ave b een s everely d epleted i n '4 C w hen t aken f rom t he e nvironment, b esides b eing s ubject t o r ecrystallisation a nd c ontamination s ince d eath. T his p aper b uilds o n t he o riginal w ork o f C happell a nd P olach ( 1972) a nd s hows t hat, o nce t he o riginal s hell s tructure h as b een r ecognised, d iagenetic c hanges c an r eadily b e i dentified u sing t he S EM a nd o ften t he l ight m icroscope. I t g oes o n t o s how t he e ffect t hat u ndetected d iagenetic m aterial c an h ave o n 1 4 C d ates m easured b y A NS.

2 39

M ethods a nd T echniques P rocedures b ased o n s table i sotope a nalysis ("C/ 1 2 C , 1 01' 0) a nd c hemistry o f s hells a nd t heir e nvironment o f d eposition a llowed s election o f s amples i n w hich a pparent a ge e ffects w ere a t a m inimum ( Yates 1 986). T hese s amples w ere t hen e xamined f or d iagenetic m aterial a nd c ontamination. I n o rder t o m ake a r eliable a ssessment o f t he e xtent a nd p osition o f d iagenetic c hanges a nd a reas o f c ontamination i t w as n ecessary t o e stablish t he f orm o f u naltered s tructures, t he l evels a t w hich d iagenetic m aterial t heir p otential f or r emoval. a ims w ere i ntegrated t o g ive s hown i n F igure 1 .

a nd c ontamination c ould b e d etected, a nd T he t echniques n ecessary t o a chieve t hese a c onsistent a nd r eliable m ethod a nd a re

After c leaning, t he m ineralogy o f i ndividual s hells w as e stablished . A nalysis o f m odern s amples c onfirmed t hat a ll t he s pecies s tudied w ere p ure a ragonite u nless t hey c ontained r egenerated s hell m aterial ( Saleuddin, 1 971). E ach s hell w as s ampled a t f ive t o t en p oints t o p rovide a m inimum s ample o f 5 0 m g f or x -ray d iffraction ( XRD) a nalysis. T he a nalyses w ere u ndertaken o n a P hilips P W 1 010 d iffractometer w ith a C uK a s ource f itted w ith a N i f ilter a nd c alibration s howed t he m inimum d etectable l imit t o b e 0 .6% c alcite. A ll s amples c ontaining c alcite a nd a n umber o f t hose t hat w ere p ure a ragonite w ere e xamined u nder a s canning e lectron m icroscope. S amples w ere c oated w ith g old/palladium i n a n a rgon a tmosphere a nd e xamined u sing a J eol 3 5CF a nd a n H itachi S -530, b oth o perating a t 1 52 5KV; u ncoated s amples w ere s tudied a t 2 -4KV. T he w orking r ange w as 3 0-80,000 t imes, s o t hat s ingle a ragonite c rystal u nits c ould b e r esolved. I f o bservation s howed t he c ontamination o r r ecrystallisation t o b e a s urface d eposit, f urther c leaning w as u ndertaken f ollowed b y f urther X RD a nalysis. W hen t he s hell w as j udged t o b e c lear o f c alcite t he w hole s hell w as e tched i n 5 % H Cl, r insed i n d istilled w ater, d ried a nd g round. T he s ample w as t hen s ubsampled a nd a gain a nalysed f or c alcite. S amples i n w hich n one w as d etected w ere c onsidered s uitable f or 1 4 C a nalysis.

S tructures P resent i n F reshwater a nd T errestrial S hells D etails o f t he s tructures o f 1 8 f reshwater b ivalves w ere a lready a vailable ( Taylor, K ennedy a nd H all, 1 969; M ackie, 1 978), a nd t he o bservations o n U nio s pecies w ere c onfirmed b y f urther s tudy. E ight s pecies o f f reshwater a nd 1 5 s pecies o f t errestrial g astropods w ere e xamined, t he s tructure o f o nly o ne s pecies b eing k nown f rom e arlier r esearch. T he n omenclature u sed i s b ased o n t hat o f T aylor, K ennedy a nd H all F ive

( 1969). s tructures

w ere

f ound

t o

b e

p resent:

c rossed-lamellar,

c omplex c rossed-lamellar, s heet n acreous, l enticular n acreous a nd p rismatic, t he l ast f our b eing p resent o nly i n t he f reshwater b ivalves.

2 40

COLLECT SA MPLE

CLEAN OUTS IDE ( 1 ) GASTROPODS RECORD ENV IRON MENTAL DATA

( 2 ) ' 4C MODERN SA MPLES ( 3 ) CHE M ICAL AND S TABLE I SOTYPE ANALYS IS ,

S ECT ION ( 1 )

MODERN SA MPLES

CLEAN I NS IDE ( 1 ) (

ETCH I N 5% HCL

GR IND SHELL c0 . 5mm

(3 )

TAKE 5 x 10mg

ETCH I N 5% HCL

SA MPLES

ARAGON ITE

CALC ITE PRESENT

HECK US ING S EM /PEEL

S EM /PEEL

ETCH I N 5% HCL

MECHAN ICA CLEAN ING

SA MPLE AND CHECK XRD

S TORE SA MPLE . FOR ' 4C

F ig.

1 .

P retreatment p rocedure f or m ollusc s hells.

2 41

(3R IND SHELL c5 m ic rons

S heet N acreous a rrangement o f

S tructure. T his l ayers p arallel t o

i s d istinguished b y t he s hell i nterior.

t he T he

r egular overall

e ffect i s o f a b rick w all, w ith t he i nterlamellar a nd i ntercrystalline o rganic matrices r epresenting t he m ortar ( Fig. 2 ). L enticular t ablets, I n

N acreous

S tructure.

f ormed o f

g eneral,

t he

p iles

o f

s urfaces

I n

t his

f orm t he

t hin l ayers,

a re

e uhedral

o r

r ounded

a re s tacked i n u neven groups.

d istorted,

l eading

t o

a more

i rregular

f orm t han t hat o f s heet n acre. P rismatic a re

S tructure.

g enerally

c onchiolin

T he

prisms

pentagonal

w alls.

T he

t hat

c ells

c ells

f orm t he basic

d ivided

a re

n arrow

n ear

r ise t o a l arge n umber o f s mall prisms. many

o f

t hese

i n

g rowth

a nd

f rom

t he

o ne

s tructural

a nother

by

u nit t hick

t he p eriostracum,

g iving

G eometric s election e liminates

c haracteristic

p rismatic

f orm

i s

p roduced. C rossed-Lamellar marine

S tructure.

g astropods,

s tructure s econd-,

i s

i ts

a nd

i s

t he

e xact

o nly

f orm

s tructure

s hows

w ide

f rom a t hree-fold h ierarchy

t hird-order

( 1974)

c oncentric margin. C omplex

f ormed

a nd

P hilippon

T his

t hough

l amellae

d escribe

r adial,

t wo

t hat

( Fig.

t ypes

d iffer

3 ).

o f

i n

f ound

i n

n on-

variation.

c onsisting

o f

MacClintock

( 1967)

c rossed-lamellar

t heir o rientation

T he

f irst-, a nd

s tructure,

t o

t he

s hell

Both t ypes o ccur i n most g astropod s hells. C rossed-Lamellar

s tructural

u nits

a s

S tructure.

t he

T his

f orm

c rossed-lamellar

i s

b uilt

s tructure

o f

but

t he w ith

s ame f our

o rientations o f c rystallites i nstead o f t wo.

Diagenetic S tructures T he

present

B ritish s urface

I sles

s tudy

o f

r evealed

e tching,

f ossil

t hree

f ormation

s hells

f orms

o f

( 3000

o f

s urface

B P

- 9 000

B P)

post-depositional

c rusts,

a nd

f rom t he c hanges:

r ecrystallization.

A ssociated w ith t hese i s t he e xfoliation o f s hell l ayers w hich a ccounts f or

t he

" flaky"

s hells.

T he

t exture

g aps

.f requently

c aused

b y

f ound

e xfoliation

o n

n on-marine

a re

g astropod

s usceptible

t o

both

c ontamination a nd t he g rowth o f s econdary c alcite. E tching. i n

T his a ppears t o r epresent t he e arliest s tages o f d issolution;

t he

t errestrial

g astropods

e xamined

t he

a ttack

was

g enerally

c onfined t o t he s urface a nd h ad p enetrated o nly a f ew m icrons. cases,

h owever,

o ccurring b elow.

i n T he

e xfoliation

e tching

o f

a ssociation w ith

i ndividual s econdary

s urfaces

a vailable

p rocesses

b ecause

f or i t

t hird-order

d eposition;

d issolution g ives

t his

a re

a ccess

I n s ome

l amellae i s

i ncreased

t o

t he

w as

d iscussed by

t he

f irst-order

l amellae i nterfaces w hich a re n ot protected b y o rganic matrices. S urface

C rusts.

s hells.

A

T his

s imilar

f orm o f s tructure

d iagenetic w as

c hange

r ecorded

w as

b y

o bserved on

E vans

s uggested i t was a s econdary d eposit o n t he o riginal The present study s uggests t hat i t c an a lso r ecrystallisation o f o riginal s hell material o n

b oth

i nner

i n t hickness.

a nd

o uter

s urfaces,

b ut

( Fig.

4 ).

( 1972),

many w ho

s hell s urface. b e f ormed by I t was observed

o nly o ccasionally

e xceeded

1 0u

T he t hickness i s l imited by t he c rust b reaking a way f rom

2 42

F ig.

2 .

D etail

o f

a s heet n acreous s tructure i n a f reshwater b ivalve

( Unio s p.).

F ig.

3 .

C rossed-lamellar s tructure i n H elix a spersa.

2 43

2 5KU Fig.

4 .

X 2600

W eathered C aerwys,

s urface

C lwyd

3 4 o f

1 0.0U

a f ossil

( 7880+150BP).

s hell

o f

C RYST C epaea h ortensis f rom

N ote t he s urface c rust

( top

r ight).

F ig.

5 .

B oundary b etween c rossed-lamellar s tructure a nd r ecrystallised c alcite ( top). F ossil s hell o f C epaea n emoralis f rom C aerwys, C lwyd

( 7880+150BPO.

2 44

t he s hell s urface, a s w as c learly s een i n a n umber o f s pecimens. T his i s a lso s een a s e xfoliation a nd i s c omparable w ith t he l oss o f t he h ydration l ayers o bserved o n o bsidian. T he e xfoliation o f c rusts m ay o we s omething t o d ifferential e xpansion o f t he s hell a ragonite r elative t o t he c alcite c rust. S uch c rusts a re b elieved t o f orm f rom t he d eposition o f s econdary c alcite f rom g roundwaters a nd, t herefore, t o c ontain c arbonate t hat i s o lder t han t he c ontext. R eplacement p eeled

o ff,

o f A ragonite b y C alcite. o r

w here

t he

W here t he s urface c rusts h ad n ot

r ecrystallisation

h ad

t aken

p lace

f rom

a n

i nner l ayer s urface, l arger a reas o f r eplacement c alcite w ere f ound ( Fig. 5 ). I n t he s hells s tudied t he a reas a ffected d id n ot e xceed 5 % o f t he s hell's v olume. T his s till r epresents, h owever, a n u nacceptably h igh l evel i n o lder s amples, a s i t u sually i ncorporates p ostd epositional C O2 . T he r ecrystallization p rocess a ppears t o c onform t o t he m odel p roposed b y P ingitore ( 1976; 1 982), w ith a n arrow d iagenetic f ront s eparating t he c alcite f rom t he u naltered a ragonite. A lthough t he f ront i s n arrow ( 1-2 m icrons), n o a pparent r etention o f t he o riginal s tructure w as o bserved .

T he E ffect o f D iagenetic C hanges o n 'm C D ates V alidation o f t he p retreatment a nd s election p rocedures r equired t he d ating o f s amples f rom a c ontext f or w hich o ther d ating w as a vailable. S amples w ere c ollected a t a n e xtensive t ufa d eposit a t C aerwys i n C lwyd, W ales f or w hich ' 'C d ates w ere a lready a vailable. T he s hells w ere s ubjected t o t he s election m ethods o utlined a bove a nd f ive s amples s ubmitted f or '4 C d ating b y t he A NS t echnique. A ccess t o t his t echnique a llowed s mall s ample s izes t o b e p repared a nd t herefore b e s ubjected t o a t horough s election p rocedure. S amples w ere g enerally 1 00 m g i n w eight b ut t wo w ere o nly 1 0 m g. D etails o f t he s amples a re g iven i n T able 1 . S amples 0 X4-6 w ere u naltered a ragonite s hell. T he d ates f or 0 X4 a nd 0 X6 w ere n ot s ignificantly d ifferent f rom t he d ate o btained o n c harcoal. S ample 0 X5 w as y ounger t han t he a ccepted d ate b y 3 50 y ears, b ut f urther S EM a nalysis s howed t hat i t c ontained s mall a reas o f r ecrystallised m aterial, p articularly b etween i ndividual l amellae. p resence o f s econdary c arbonate c ould e xplain t he a ge e rror a nd d irection. S amples 0 X13 a nd 0 X14 w ere d iagenetic d eposits; 0 X13 r ecrystallised m aterial ( calcite) a nd 0 X14 a s urface c rust. p redicted t hey w ere i n e rror a nd i n t he e xpected d irection.

T he i ts w as A s

C onclusion T he w ork d ealt w ith i n t his p art o f t he p roject h as s hown t hat o ne o f t he t wo m ajor p roblems a ssociated w ith t he u se o f n on-marine s hells f or ' 'C d ating c an b e r educed t o l ow l evels a nd i n t he c ase o f s elected s amples c onfined t o w ithin t he s tatistical e rrors a ssociated w ith c ounting. T o a chieve t his r equires a r igorous a pproach t o t he c leaning a nd p reparation o f m aterial f or d ating a nd i n t his t he S EM p lays a n i mportant r ole.

2 45

r n

0 C

c o

e

I f )

I f )

N

C N I I

, 1 I

0 I

C f ) C f )

r -

N , 1 P O

0 N

0

0

0

0

8 9 0 + / 6 5 0

N

c p N

h o r t e n s i

. . . L c )

6 3 0 + / 6 0

. . . e

. . . .

n e m o r a l i s

. . , m

. . .

7 8 6 0 + / 1 0

c o

7 5 3 0 + / 1 0

c o

h o r t e n s i

g I

7 9 5 0 + / 9 5

c 0

a e n e m o r a l i s

C O

S p e c i e s o f S h e l

0

C . ;

C . ;

o C r )

E l

r n ‘ i X 0

c . )

2 46

e , i X 0

Acknowledgements I s hould C rystallography

l ike t o t hank C . i n B irkbeck C ollege,

i n U niversity C ollege L ondon, a nd a dvice.

V ita-Finzi, t he D epartment o f L ondon, t he D epartment o f G eology

a nd t he A ccelerator U nit,

O xford f or h elp

T he work w as f unded b y t he N ERC.

References C allen, R .A ., Wasson, R .J. a nd G illespie, R . 1 983. R eliability o f r adiocarbon d ating o f p edogenic c arbonate i n t he A ustralian a rid z one. S edimentary G eology 3 5: C happell, J . a nd r ecrystallisation m olluscs. E vans,

1 -14.

P olach, o n '4 C

H .A . d ating

Quaternary R esearch 2 :

J .G.

1 972.

L and S nails

1 972. S ome e ffects o f l ate P leistocene

o f partial c orals a nd

2 44-252.

i n Archaeology.

L ondon a nd N ew York:

S eminar P ress. E vin,

J .,

Marechal,

C onditions

i nvolved

J ., i n

P achiaudi,

d ating

C .

K ra, R .S. ( eds.), I nternational R adiocarbon 2 2: 2 : 5 45-555.

1 4

C

G illespie, R . a nd P olach, H .A . 1 979. f or r adiocarbon dating o f Australian S uess, N inth

H .E.

( eds.),

P roceedings,

R adiocarbon pp.

a nd

t errestrial

I n

C onference

J .J.

1 980.

S tuiver,

T enth

M .

a nd

P roceedings:

T he s uitability o f marine s hells prehistory. I n B erger, R . a nd

D ating

4 04-421.

P uissegue,

s hells.

I nternational

B erkeley:

1 4

University

C C onference, o f

C alifornia

P ress. MacClintock, b ellerophontoid

C . 1 967. S hell s tructures gastropods ( Mollusca). P eabody

H istory B ulletin 2 2: Mackie,

G .L.

1 -140.

1 978.

E lectron

J ournal o f Z oology 5 6: M angerud,

J .

d iscussion

1 972.

o f

o f patelloid a nd Museum o f Natural

1 :

m icroscopy

R adiocarbon

a pparent

o f

P isidiiae.

Canadian

1 -6.

a ge

o f

d ating

o f

marine

s hells,

r ecent s hells f rom N orway.

i ncluding a B oreas

1 :

2 :

1 43-172. O lsson, o f

I .U.,

s toring

G öksu, Y .

a nd

a nd S tenberg,

t reatment

o f

A .

F oraminifera

1 968.

F urther i nvestigations

a nd molluscs

G eologiska F oreningens i S tockholm F orhandlinger 9 0: P hilippon, c oquille C entre

J .

1 974.

S tructure

d e G astropodes

pour

E tudies

e t

a ctuels

e t

e t

R echerche

c omposition

f ossiles.

P aleontologie

'4 C d ating.

m ineralogique

N otes e t

f or

4 17-426.

e t

d e

l a

C ontributions,

B iostratigraphie

7 :

1 -84. P ingitore, products

N .E. a nd

P etrology 4 6:

1 976.

t heir

V adose

r ecognition

a nd i n

9 85-1006.

2 47

P hreatic c orals.

d iagenesis: J ournal

o f

processes, S edimentary

P ingitore,

N .E.

d iagenesis.

1 982.

T he

r ole

o f

d iffusion

J ournal o f S edimentary P etrology 5 2:

d uring

S aleuddin, A .S.M. 1 971. F ine s tructures o f n ormal a nd s hell o f H elix. C anadian J ournal o f Z oology 4 9: 3 7-41. T aylor, a nd

J .D.,

K ennedy,

m ineralogy

T rigonacea.

R . S.

O tlet, f rom

( eds.),

R adiocarbon 2 2: V ita-Finzi, P ersian

I nternational

t he

H all,

A .

1 969.

I .

B ritish

1 4

3 :

T he

s hell

I ntroduction.

M useum

( Natural

s tructure N uculacea-

H istory)

Z oology

a nd

S weeting, 1 4

UK C

M .M.

t ufa.

1 980. I n

C onference,

S tuiver, T enth

H ydrological M .

a nd K ra,

P roceedings,

8 97-908.

1 980.

a nd 1 4

R .L.

C profiling o f

International

C .

G ulf

o f

a nd

B ivalvia.

r egenerated

1 -125.

P .M.,

i mplications

W .J.

t he

B ulletin

S upplement 3 : T horpe,

o f

c arbonate

2 7-39.

l' C

d ating

I ranian M akran. C

C onference,

o f

r ecent

I n S tuiver,

T enth

c rustal movements M .

P roceedings,

a nd K ra,

R .S.

R adiocarbon

i n

t he

( eds.), 2 2:

3 :

7 63-773. V ita-Finzi, 1 4 C d ating.

C . a nd R oberts, N . R adiocarbon 2 6: 1 :

1 984. 5 4-58.

S elective l eaching o f s hells f or

Y ates, T .J.S. 1 986. T he s election o f n on-marine M olluscan s hells f or r adiocarbon d ating. U npublished P h.D. t hesis, U niversity o f L ondon.

2 48

T HE S CANNING E LECTRON M ICROSCOPE A ND THE S TUDY O F ANCIENT T EETH S imon H illson

A ncient

t eeth

a rchaeological

f orm

s ites

a p rominent

a nd d ental

p art

t issues

o f

t he

mammal

r emains

f rom

a re o ften p reserved r elatively

i ntact. U sually, t he e namel, w hich c oats t he c rown o f t he t ooth i s t he b est-preserved. D entine, w hich f orms t he m ain i nternal s tructure o f t he t ooth a nd c ement, w hich c oats t he r oot s urfaces ( and c rown i n s ome m ammals), m ay b e l ess w ell-preserved, b ut i t i s o ften p ossible e xamine t he d etailed m icroscopic s tructure o f a ll t hree t issues.

t o

T he p olarising m icroscope h as b een t he s tandard p iece o f e quipment f or s tudying t he h istology o f d ental t issues. A s ection o f t he t ooth, p olished t o a t hickness o f l ess t han 1 00 m icrons, i s e xamined i n t ransmitted l ight. P olarising f ilters a re a rranged a bove a nd b elow t he m icroscope s tage, s o t hat t he b rightness a nd c olour o f t he i mage r eflects t he m ineralogy a nd o rientation o f c rystals, c ollagen f ibres a nd p ore s paces i n t he t issue. A s d ental t issues a re l argely c omposites o f m ineral c rystals ( the a patite f amily o f c alcium p hosphate m inerals) a nd c ollagen f ibres, t his m akes i t p ossible t o s ee m any d etails o f s tructure w hich c annot b e d iscerned b y o ther m eans. F or t his r eason, m uch w ork i n d ental h istology a nd i ts a rchaeological a pplications h as b een c arried o ut u sing t he p olarising m icroscope ( Schmidt a nd K eil, 1 971; R ose e t a l., 1 981; R udney, 1 983; H illson, 1 986). T ransmitted l ight m icroscopy o f t his k ind d oes, h owever, h ave a n umber o f d isadvantages. F irst o f a ll, i t c annot r esolve d etails l ess t han 1 m icron o r s o a cross. I n a ddition, i t i s n ecessary t o p repare p olished v aluable

t hin s ections s pecimens a nd

o f t eeth, w hich i s t ime c onsuming, d estroys c an b e d ifficult w ith f ragile a rchaeological

m aterial. F inally, t he m aterial b eing e xamined m ust b e t ranslucent a nd, w hilst t his i s n o p roblem w ith m ost f resh d ental m aterial, a rchaeological s pecimens a re f requently r endered o paque b y t he p rocesses o f p reservation. S uch d ifficulties v ary f rom s ite t o s ite a nd, a lthough i t i s o ften p ossible t o p roduce u sable s ections o f d ental e namel, d entine a nd c ement a re o ften t oo f ragile, t oo a ltered, o r t oo o paque. U se o f t he s canning e lectron m icroscope c an a void m any o f t hese p roblems. I t h as a h igh r esolution a nd l arge d epth o f f ocus, a nd s tructures m uch l ess t han 1 m icron a cross c an b e e xamined r outinely. I t l ooks a t s urfaces, n ot s ections s o t hat t he s pecimen d oes n ot n eed t o b e t ranslucent. P reparation t echniques c an b e v ery s imple. S mall f ragments o f t issue, a lready b roken a nd l ying i n t he b ottom o f a b ox, c an b e u tilised. R eplicas c an b e m ade u sing s ilicone r ubber o r o ther m ethods ( see C laugher, t his v olume) w ithout d amaging t he s pecimen a t a ll, w hilst s till s howing s ufficient s tructural d etail. S canning e lectron m icroscopy d oes n ot d emonstrate w ell a ll t he f eatures t hat c an b e s een i n p olarising m icroscopy, b ut i t i s a ble t o s how s ome f eatures t hat p olarising m icroscopy c annot; e ither b y v irtue o f i ts g reater m agnification, o r b ecause i t i s p ossible t o l ook a t s urfaces w hich h ave b een f ractured a long t he T his p aper p resents t hree e xamples o f w ays

2 49

" grain" o f t he t issue. i n w hich t he s canning

e lectron m icroscope c an y ield u seful o ne f rom e ach o f t he d ental t issues.

i nformation

f or

a rchaeologists;

E namel a nd I dentification T he t iny a patite c rystals o f d ental e namel a re a rranged i nto s mall b undles, a bout 5 m icrons a cross, c alled p risms ( Fig. 1 ). T hree m ain p atterns o f e namel s tructure c an b e d istinguished f rom t he w ay i n w hich t he p risms a re a rranged ( Boyde, P attern

3 ;

w hich

i s

t he

1 965): m ost

c ommon

f orm

i n

m an

a nd

t he

carnivores and elephants, p roduces a c haracteristic t essellation w hen t he p risms a re s een e nd-on ( Fig. 2 ).

a pes,

" keyhole"

P attern 2 ; t he m ain p attern o f h oofed mammals, m onkeys a nd m arsupials, a nd w hich i s t he b asis o f e namel s tructure i n r odents ( below), h as " inter-row s heets" o f e namel a rranged b etween r ows o f p risms ( Fig. 3 ). P attern 1 ; f ound i n t he t oothed w hales, b ats, i nsectivores a nd s ome o f t he l emurs, i s t he most s imple f orm, w ith c ylindrical p risms r unning t hrough t unnels i n t he " interprismatic" e namel. T hese p atterns v ary g reatly a nd m ost t eeth h ave a t l east s ome o f a ll t hree d istributed t hrough t heir e namel, b ut t here a re s ome g eneral d ifferences b etween g roups o f m ammals. B oyde a nd M artin ( 1982) w ere a ble t o d istinguish b etween m an a nd g roups o f g reat a pes i n t he r elative p roportions o f P atterns 3 t o P atterns 1 a nd i mportant i mplications f or t he s tudy o f h ominid f ossils.

2 .

T his

h as

T here a re, h owever, f urther p ossibilities f or d istinguishing b etween d ifferent g roups o f mammals o n t he s tructure o f t heir e namel. T he p risms o nly r arely p ass s traight t hrough t he e namel. I n m ost mammals, t hey b end f rom s ide t o s ide a nd a re w oven i nto o ne a nother ( Fig. 5 ). T his i s c alled p rism d ecussation. T he w eave i s c omplex a nd v ariable, b ut i t s eems p ossible t o m ake s ome g eneral d istinctions b etween t he f ollowing mammal g roups ( Kawai, 1 955):

1 . 2 .

T oothed w hales, C arnivores.

i nsectivores a nd b ats. P innipeds

c arnivore p attern,

( seals

a nd

s ea

l ions)

f it

i nto

t he

b ut d iverge t oward t he p rimate f orm.

3 .

P rimates.

4 .

U ngulates ( hoofed mammals). T here s eem t o b e s ome g rounds f or d istinguishing b etween e ven-toed ( cattle, d eer, e tc.) a nd o dd t oed ( horses a nd r hinoceros) u ngulates o n t he b asis o f t heir d ecussation p attern.

5 .

R odents

a nd

l agomorphs

c omplex p atterns d istinguish

o f

b etween

a ll,

( rabbits s o

a nd

h ares)

h ave

t he

m ost

c omplex t hat i t m ay b e p ossible t o

r odent f amilies a nd e ven

2 50

g enera

o n

t he

F ig.

1 .

e lectron

P risms

i n m edieval human e namel f rom Y ork,

m icrograph

o f

f ractured

s urface.

S cale

E ngland. bar

S canning

r epresents

1 0

m icrons.

F ig.

2 .

a re

s een

e lectron m icrons.

P attern 3 e namel i n t he s ame s pecimen a s F igure e nd

o n,

m icrograph

a nd o f

s how

a

r oughly

f ractured

" keyhole"

s urface.

2 51

S cale

1 .

o utline. bar

T he prisms S canning

r epresents

1 0

b asis o f t heir e namel B oyde, 1 978).

( Korvenkontio,

1 934; Y amakawa,

1 959;

T he l arge r odent i ncisor s hown i n F igure 4 i s a n e xample o f t he u se o f e namel s tructure a s a n a id t o i dentification. F rom i ts m orphology, i t i s a n u pper l eft i ncisor, b ut b ecause m ost r odent i ncisors a re b uilt a long s imilar l ines t here a re f ew d efinite c lues a s t o i ts s pecies. I t i s v ery l arge - t he w orn s urface i s a bout 5 m m a cross - a nd t his n arrows d own t he c hoice. I t c omes f rom a N eolithic s ite i n T unisia a nd t he o nly O ld W orld H olocene r odents w hich w ould b e l arge e nough a re b eaver C astor o r p orcupine H ystrix ( Hillson, 1 986). B ecause i t c omes f rom t he N orth A frican c oast, i t i s a lmost c ertain t o b e p orcupine, b ut i t i s s till d esirable t o c onfirm t he i dentification. F ortunately, t he w eave o f p risms i n b eaver e namel i s v ery d ifferent f rom t hat o f t he p orcupine. I t c onforms t o a p attern k nown a s s ciuromorph, w hereas t he p orcupine f its i nto a n h ystricomorph p attern. S canning e lectron m icroscope e xamination o f a s mall f ragment o f t he N eolithic s pecimen ( Fig. 5 ) c onfirms q uickly t hat i t i s h ystricomorph i n f orm, a rranged i nto a lternate b ands o f d ifferent p rism o rientation, e ach 3 t o 5p risms a cross. S imilar s tudies m ay b e c arried o ut i n o ther r odent t eeth. F or e xample, t he s canning e lectron m icroscope h as b een u sed i n t he s tudy o f e volution i n f ossil v ole c heek t eeth ( von K oenigswald, 1 980). I n g eneral,

h owever,

t he t echnique h as b een l ittle a pplied i n a rchaeology.

A ge D etermination a nd R oot D entine T ranslucency T here a re s everal f orensic m ethods f or d etermining a ge a t d eath f rom h uman t eeth. S ome o f t hem c ould p otentially b e a pplied t o archaeological m aterial, b ut c are i s n eeded. C onditions o f p reservation m ay c ause c hanges i n t he d ental t issues w hich m ask t he e ffects u sed i n a ge d etermination, o r c onfuse t he i ssue. T his i s w here t he s canning e lectron m icroscope m ay h elp. O ne p otentially u seful m ethod i nvolves e xamining a s ection o f t he t ooth r oot a nd l ooking f or a n a rea o f t ranslucency i n t he d entine. N o m agnification i s r equired - t he e ffect c an b e c learly s een w ith t he n aked e ye o n a l ightly p olished s lice t hrough t he t ooth ( Fig. 6 ). I n m ost i ndividuals t he s ize o f t he t ranslucent z one i s c orrelated w ith i ncreasing a ge a nd, i f i t i s m easured, t hen s tandard f ormulae c an b e u sed t o c alculate a n e stimate o f t he a ge a t d eath ( Bang a nd R amm, 1 970). T he m ethod i s p articularly u seful i n d etermining t he a ge o f o lder a dult p eople a nd t his i s i ts m ain a ttraction i n a rchaeology, w here i ndividuals o ver 2 5 o r s o y ears a re d ifficult t o a ge r eliably b y o ther m eans. U nder t he s canning e lectron m icroscope, d entine ( Fig. 7 ) i s c haracterised b y c losely s paced t ubules w hich r un t hrough t he t issue. T hese a re 4 m icrons o r l ess i n d iameter a nd t heir s tructure i s d ifficult t o s ee u nder t he p olarising m icroscope. T he d entine b ecomes t ranslucent a s t he t ubules a re p rogressively i nfilled o ver t ime. I n a rchaeological s pecimens, p oor p reservation m ay m ake s ee t he l imits o f t he a rea o f t ranslucency w ith t he d entine m ay b e o paque b ecause

i t d ifficult t o n aked e ye. T he

t he c ollagen f ibres a nd a patite c rystals

2 52

F ig. T he

3 . P attern p risms a re

i nterprismatic f ractured,

F ig.

4 .

T unisia.

2 e namel i n m edieval p ig s een e nd o n, a rranged

e namel

b etween

e tched s urface.

L arge

r odent

t hem .

e namel f rom Y ork, E ngland. i n r ows w ith s heets o f

S canning

e lectron

S cale b ar r epresents

i ncisor

S cale b ar r epresents

( upper 0 .5 c m.

2 53

r ight)

m icrograph

o f

1 0 m icrons.

f rom a N eolithic

s ite

i n

e ir

F ig.

5 .

E namel

f rom t he

s pecimen

i n F igure

4 ,

s howing

h ystricomorph

s tructure. I n t he l ower h alf o f t he p hotograph, t he p risms a re a rranged I nto b and, 5 o r s o p risms w ide, w hich p resent t hemselves t o t he p lane o f s ection a t d ifferent a ngles. S canning e lectron m icrograph o f p olished,

e tched s urface.

S cale b ar r epresents 2 5 m icrons.

2 54

F ig.

6 .

c entral)

P olished f rom

s ection

T unisia .

T he

t he t ooth e xtends d ownwards, s een

a s

a d arker

a rea

t hrough

N eolithic

s pecimen

i s

human

a rranged

s o

i ncisor

t hat

t he

( upper r oot

o f

a nd t he z one o f t ranslucent d entine c an b e

e xtending

b ack

r epresents 0 .5 c m .

2 55

f rom

t he

r oot

t ip.

S cale b ar

h ave b een r eplaced b y o ther m inerals w hich c rystallise o ut f rom t he g round w ater, o r t he t ooth r oots m ay h ave b een i nvaded b y m yceliump roducing m icroorganisms. T hese i nvasions c arve o ut i rregular c anals ( Fig. 8 ), u p t o 2 0 m icrons o r s o i n d iameter, w hich g reatly d isrupt t he d entine s tructure a nd c an o bscure t he e dge o f t he t ranslucent z one. T he s canning e lectron m icroscope c an b e u sed t o e xamine t he d entine w hich r emains i n b etween t he c anals o f t he i nvading m ycelium , a nd c heck t he i nfilling o f t ubules. F or e xample, p arts o f t he t ranslucent z one s hown i n t he t ooth s ectioned i n F igure 6 s how c learly, b ut t owards t he e dge o f t he z one, t here i s a l arge p ale p atch o f d entine w hich h as b een i nvaded a nd w here t he d etail i s o bscured. U nder t he s canning e lectron m icroscope ( Fig. 8 ) i t w as p ossible t o e xamine t he t ubules i n b etween t he d amaged a reas a nd t o d elimit t he a rea w ith i nfilled t ubules. S pecimen p reparation w as s imple; t he h alf o f t he t ooth w hich r emained a fter t he s lice h ad b een c ut w as p olished, e tched a nd t hen c oated w ith g old. A nother m ethod w ould b e t o p roduce a r eplica a fter e tching. T he a verage l ength o f t he t ranslucent z one i n t his s pecimen y ields a n a ge a t d eath e stimate o f 6 8 + /- 1 1 y ears i f t he s tandard f ormulae f or m odern m an a re a pplied ( Bang a nd R amm,

1 970).

C ement Layers a nd Age T he

c ement

c oating

o f

t he

r oots

i s

f requently

l ayered.

I n m any

m ammals, t hese l ayers a ppear t o b e l aid d own s easonally o r a nnually. T his i s p articularly s o i n t he m arine mammals s uch a s t oothed w hales o r s eals a nd s ea l ions ( Perrin a nd M yrick, 1 980), b ut a lso s eems t o b e t he c ase i n t errestrial h oofed mammals, h ibernating m ammals ( Klevezal a nd K leinenberg, 1 967; M orris, 1 972; C asteel, 1 976) a nd e ven m an h imself ( Stott

e t

t o

s een

b e

m odest

a l., i n

1 982). s imple

I n m any m ammals, s lices

m agnification.

t hrough

A nother

t hese

t he

m ethod

l ayers

t ooth i s

t o

a re b road e nough

r oot,

e xamined

d ecalcify

t he

u nder t ooth

( usually w ith a cids), l eaving t he o rganic c omponent ( mostly c ollagen f ibres) w hich c an t hen b e s ectioned w ith a m icrotome a nd s tained b efore b eing e xamined i n a c onventional o ptical m icroscope. C ounts o f t he p atterns o f l ayers a re t hought t o y ield e stimates o f t he a ge a t d eath, a lthough t here a re d ifficulties w ith t he p rocedure ( Hillson, 1 986). T he l ayers a re n ot a lways c learly d efined a nd d ifferent o bservers o ften p roduce d ifferent c ounts. I n a ddition, t he s easonal b asis o f t he l ayering i s n ot c learly u nderstood, a nd t he r elationship b etween l ayer p attern c ounts a nd a ge i s n ot p roven i n a ll mammals. C autiously a pplied, h owever, t he m ethod d oes s eem t o h ave p romise a nd i t w ould b e v ery u seful t o a pply i t i n a rchaeology. A s

i n

t he

c ase

o f

r oot

d entine

t ransparency

( above)

a s imple

p olished s lice t hrough t he t ooth w ill o ften s uffice t o s ee t he c oarser l ayering s uch a s i s f ound i n t he h oofed mammals. I t i s m ore d ifficult t o s ee t he f iner l ayering s hown i n o ther mammals, a nd t he d etails may o ften b e o bscured b y p oor p reservation. T he s canning e lectron m icroscope c an b e u sed t o e xamine c ement l ayers i n r oot f ragments w hich h ave b een e tched t o b ring o ut t heir s tructure i n r elief. F igure 9 , f or e xample, i s a s pecimen o f c ement f rom a c ave b ear ( Ursus a rctos s pelaeus) c anine, f ound a t a M ousterian c ave s ite i n Y ugoslavia. T he l ayers a re n ot s harply d efined, b ut i t i s p ossible t o c ount s ome 2 0 m ajor

l ayer g roups t hrough t he t hickness o f t he

2 56

c ement.

E xperimental

F ig. a s

7 .

D entinal

F igure

1 ).

t ubules S canning

S cale b ar r epresents

i n m edieval h uman d entine e lectron

m icrograph

o f

( the s ame s pecimen f ractured

s urface.

1 0 m icrons.

F ig. 8 . " Canals", p robably d ue t o i nvasion b y a m ycelium-producing m icroorganism, i n t he s ame s pecimen a s F igure 6 . T he c anals ( on t he l eft o f t he p hotograph) a re f illed w ith a r oughly t extured d eposit o f s econdary m inerals, d eposited f rom g round w aters p ercolating t hrough t he t ooth d uring b urial. T he d entine i s f rom t he t ransparent z one a nd t he t ubules, w hich c an b e s een i n b etween t he c anals, a re f illed w ith l ater d entine d eposits w hich h ave e tched o ut t o s how a s c ores. S canning e lectron m icrograph o f p olished, e tched s urface. S cale b ar r epresents 1 0 m icrons.

2 57

w ork

n eeds

k nown a ge, I t

may

r emains. l ayer

t o

c ount

s ections.

d one

a lso

Human

b e

a ll

t he

a re

b e

a rctos

s pecimens

h as

t eeth

o f

f or

s imilar

f inely

t o

f rom

i ndividuals

o f

t echniques

s paced

a ge.

S tott

m icroscopy

t o

l ayers, e t

o f

human

a nd

a l.

t he

( 1982)

polished

t hin

y ields much d etail o f c ement l ayering

human

t eeth,

e lectron m icroscope

s uitable;

o f

a pply

p olarising r arely

e xample,

b ut e tched c ement s urfaces

f requently d o s how l ayers.

t he

s pecimen

i n

F igure

N ot

6 d id n ot

s o t hat c ounts c ould n ot b e c ompared w ith t he r oot

t ransparency m ethod

s econd molar

t o

r elated

u sing

h ave c lear l ayering, d entine

U .

f requently

t echnique

s canning

t eeth

m odern

possible t o

t his

T his

a rchaeological

u nder

o n

c ement

s eems

demonstrated i n

b e

but t here d oes s eem t o b e s ome p otential f or t he method.

a bove.

I n

a nother

a y oung man f rom N ubia

make a c ount ( Fig. 1 0). places o n t he r oot a nd,

( c.

s pecimen,

1 700 B C),

T hirteen t o 1 5 l ayers s ince t he s econd m olar

h owever,

t he

i t i s possible t o

a re v isible i n many r oots a re c ompleted

a round 1 4 y ears o f a ge, t his w ould s eem t o s uggest a n a ge e stimate o f 2 7 t o 2 9 y ears. T his c ompares f avourably w ith i ndependent e vidence f rom t he s keleton o f t his i ndividual. M uch more s eem

t o

b e

w ork

n eeds

r eal

t o b e d one o n t hese t echniques,

possibilities

m icroscope t o e xpand t he r ange f rom a ncient d ental r emains.

f or

o f

u sing

t he

i nformation

b ut t here d o

s canning

w hich

c an b e

e lectron e xtracted

References B ang,

G .

a nd Ramm,

E .

1 970.

d entine t ransparency. B oyde, I n

A .

1 965.

S tack,

M .V.

S ymposium

F earnhead,

t he

C omposition,

T ooth E namel,

pp.

1 63-167.

A .

3 -35.

T he s tructure o f d eveloping mammalian d ental e namel.

a nd

o n

B oyde,

D etermination o f a ge i n humans f rom r oot

A cta O dontologica S candinavica 2 8:

1 978.

R .W .

( eds.),

P roperties

B ristol:

D evelopment

o f

T ooth E namel,

a nd F undamental

I nternational S tructure

o f

Wright. t he

s tructure

o f

t he

e namel o f

t he

i ncisor t eeth i n t he t hree c lassical s ubordinal g roups o f t he R odentia. I n

B utler,

P .M.

a nd

E volution o f T eeth, B oyde,

A .

J oysey,

pp.

a nd M artin,

L .

K .A .

4 3-58. 1 982.

( eds.),

L ondon:

D evelopment,

F unction

a nd

A cademic P ress.

E namel m icrostructure d etermination i n

h ominoid a nd c ercopithecoid primates.

Anatomy a nd E mbryology 1 65:

1 93-

2 12. C asteel,

R .W.

1 976.

a rchaeological

value.

( Berkeley)

1 -27.

H illson,

4 7: S .W.

1 986.

I ncremental P apers

T eeth.

o f

g rowth t he

z ones

K roeber

C ambridge

i n

mammals

a nd

A nthropological

M anuals

i n

t heir

S ociety

A rchaeology.

C ambridge U niversity P ress. K awai, N . 1 955. C omparative a natomy o f O kajimas F olia Anatomica J aponica 2 7: 1 15-131.

2 58

t he

bands

o f

S chreger.

K levezal, mammals U SSR,

G .A .

f rom

a nd

t ranslated

F oundation,

K leinenberg,

a nnual U S

l ayers

1 969

i n

S .E.

t eeth

D epartment

D epartment

o f

o f

t he

n agerincisiven A nnal.

Z ool.

M orris,

V . A . u nter

S oc.

P .

P errin,

Z ool.

1 972.

Mammal R eview 2 :

1 934.

h inweis

A r eview

a nd N ational

C learinghouse

o f

F ederal

u ntersuchungen

s chmelzstruktur

Van.

2 :

a n

d er b ackenzahne.

1 -274.

mammalian

a ge

d etermination methods.

a nd

Myrick

i n

a ge

d etermination.

A .C .

G rowth

o f

odontocetes

P roceedings

o f

C alifornia,

S eptember

5 -19,

1 978.

a nd

t he

C onference o n D etermining A ge o f Odontocete C eteans J olla,

S cience

f or

6 9-104.

W .F.

p roblems

I nterior

o f

S ciences

S pringfield.

d ie

F enn.

d etermination

A cademy o f

Mikroskopische

a uf

Bot.

A ge

bones.

C ommerce,

S cientific a nd T echnical I nformation, Korvenkontio,

1 967. a nd

s irenians:

I nternational

( and S irenians),

C ambridge:

L a

I nternational

W haling C ommission. R ose,

J .C.,

indicator

B oyd, o f

L .F.

a nd

c hildhood

C ondon,

s tress

K .W .

i n

1 981.

American J ournal o f P hysical Anthropology 4 9: R udney, o f

J .D.

g rowth

1 983.

S chmidt,

S tott, a ge

W .J.

a nd

Oxford:

G .G.,

S is,

c riterion

i n

s keletal

e namel

s amples.

5 11-516.

T he a ge-related d istribution o f d ental i ndicators

d isturbance

i n

a ncient

h ypotheses o f X -group o rigins.

T issues.

H istological

prehistoric

K eil,

A .

Lower

N ubia:

i mplications

J ournal o f Human E volution 1 2: 1 971.

f or

5 35-543.

P olarization M icroscopy o f

D ental

P ergamon P ress. R .F.

a nd L evy,

f orensic

B .M.

1 982.

d entistry.

C emental a nnulation a s a n

J ournal

o f

D ental

R esearch

6 1:

8 14-817. v on K oenigswald, W . 1 980. S chmeltzstruktur u nd m orphologie i n d en molaren d er Arvicolidae ( Rodentia). Abhandlungen d er S enckenbergische N aturforschende G esellschaft 2 39: Yamakawa,

K .

s tructure

o f

1 959. t he

1 -29.

C omparative

r odents

( in

a natomical

J apanese).

8 52-866.

2 59

s tudies

A cta A natomic

o n

t he

e namel

N ipponica

3 4:

F ig. 9 . M ousterian f ractured, m icrons.

L ayers i n c ement f rom a c ave b ear c anine, f ound a t a c ave s ite i n Y ugoslavia. S canning e lectron m icrograph o f e tched s urface. S cale b ar r epresents a pproximately 5 00

F ig. 1 0. L ayers i n h uman c ement f rom K erma, N ubia ( c. S canning e lectron m icrograph o f p olished, e tched s urface. r epresents 5 0 m icrons.

2 60

1 700 B C). S cale b ar

A CTUALISTIC S TUDIES O F A NIMAL R ESOURCES A ND H OMINID ACTIVITIES P at S hipman

T heoretical F ramework

m y

A lthough t he o stensible p urpose o f t his p aper i s t o r eview s ome o f w ork i n u sing t he S EM t o r esolve a rchaeological p roblems I s hall

b egin b y a ddressing a m ore c rucial i ssue: w hat i s t he m eaning o f t he a nswers? U ntil t his i ssue i s c learly u nderstood, a nd e xplicitly s tated, t here i s l ittle p oint i n d iscussing t he t ypes o f q uestions t hat c an b e a nswered. I t i s a ll t oo c ommon f or r esearchers t o l ose s ight o f t he s ignificance a nd l imits o f r esolution o f t he a nswers i n t he s truggle t o o btain a ny a nswers a t a ll. I n 1 978, I f irst b egan e xploring t he u sefulness o f t he S EM a s a t ool t hat w ould p rovide n ew t ypes o f d ata a bout f ossil b ones. M y i nterests w ere p rimarily i n f inding n ew a nd m ore p owerful m eans o f d educing t he t aphonomic h istory o f s pecific s ites a nd t o t his e nd I b egan c ollecting b ones o f k nown t aphonomic h istory, e ither n aturally o r e xperimentally p roduced. S tructurally, t he p roblems I f aced a t t he t ime w ere o nes t hat a re u ndoubtedly f amiliar t o m ost o r a ll o f t he p articipants i n t he c onference o n t he S EM i n A rchaeology t hat p roduced t his b ook. T hat i s, I w as f aced w ith a v ast v irgin t erritory. T o m y k nowledge, n o o ne p rior t o t hat t ime h ad c onsidered t hat b ones m ight e ncode i n t he m icroscopic m orphology o f t heir s urfaces t he s et o f t aphonomic e vents w hich t hey h ad u ndergone. T here w as n o d ata b ase f rom w hich t o o perate, n o c omparative s ample t o w hich u nknowns ( fossils) c ould b e c ompared a nd t hen d iagnosed ( their h istory d educed). I

d rew

u p

e xperiments e xposed

a l ist

u nder

d ocumenting

o f

m ajor

a nd c ollecting n atural

t he

t aphonomic

" wild b ones",

c onditions

s urface

t o

c hanges

e vents t hat

d ifferent

t hat

h ad

a nd

i s,

b egan

t hose

t aphonomic

o ccurred.

c onducting

t hat

h ad b een

e vents,

A s

t his

a nd w ork

p roceeded, t he l ist o f e vents t hat I f elt w ere i mportant g rew g eometrically, a s d id t he c ollection o f r eplicas o f c ontrols. T he f irst s ynthesis o f t his e xploratory w ork c an b e f ound i n S hipman ( 1981a); a dditional s tudies r elevant t o a rchaeological p roblems a re a lso i n p rint a nd s ome a re s ummarized b elow ( Shipman, 1 981b, 1 986a, b , a nd i n p ress; S hipman a nd R ose, 1 983, a nd C hapter 2 1, t his v olume; S hipman e t a l., 1 984a, b ). T he t heoretical u nderpinnings o f t his w ork, a s i n a ll a ctualistic s tudies, i s f airly s traightforward. A lthough I h ave d iscussed i t i n d etail e lsewhere ( e.g., S hipman, 1 981a: 3 59-360; S hipman, 1 981b: 1 01 2), i t i s w orth r epeating h ere b ecause i t i s o f s uch f undamental i mportance. A rchaeology, t aphonomy, a nd p alaeontology a re a mong t he h istorical s ciences i n w hich t he t ask i s n ot t o p redict t he f uture o utcome o r e ffects o f a g iven s et o f e vents b ut r ather t o r etrodict t he s et o f e vents t hat g ave r ise t o a p articular e ffect. H istorical s cientists a re f orever " discovering" t he r esults o f e xperiments a nd t hen t rying t o d educe w hat t he e xperiment i tself w as. T he c onsequence o f

t his

i s

t hat,

s tructurally,

h istorical

2 61

s ciences

m ust

o perate

b y

a

u nique s et o f r ules. q uestions F irst, a n

S impson

( 1970) p roposed t hat t he i nvestigation o f

i n t he h istorical s ciences u nderstanding o f t he c ausal

m ust r ely u pon t hree s tages. l inks b etween m odern p rocesses

a nd t heir e ffects m ust b e a chieved; t hen o f a ncient p rocesses) m ust b e g athered;

t he h istorical d ata ( effects f inally, t he h istorical d ata

c an b e c onfronted a nd i nterpreted u sing t he u nderstanding o f t he p rocess-effect l inkage g ained f rom t he s tudy o f m odern d ata. T his a pproach i s f undamental t o a ll a ctualistic s tudies, i ncluding t hose i n w hich t he S EM i s u sed t o r esolve a rchaeological p roblems. T heoretically s ound t hough t his a pproach m ay b e, i n p ractice i t i s d ifficult. O ne c annot, r easonably, s tudy a nd c omprehend a ll m odern p rocesses t hat m ight b y a ny s tretch o f t he i magination h ave a ffected a f ossil o r a rchaeological a ssemblage. E ven w orse, i f o ne c ould, t he s tudy w ould s till b e l imited b y w hat o ne i magined w as r elevant o r l ikely t o h ave h appened, a nd o ne w ould s till f ace t remendous d ifficulties i n d ealing w ith t hose a spects o f t he p ast t hat a re n ot r eplicable t oday. A s imple e xample w ill d emonstrate w hat I m ean. S uppose t he q uestion c oncerned t he e ffects t hat a nimals' t eeth h ave o n b ones. T he e xperiments w ould s eem t o b e s imple: g o t o a z oo, f eed a nimals b ones, c ollect a nd s tudy t he b ones. T hen, f or g ood m easure, t ry t o f ind " wild b ones" o f a nimals k illed o r p rocessed b y c arnivores, j ust i n c ase t he z oo a nimals w ere b ehaving a typically. B ut w hat a bout e xtinct c arnivores? W hat m arks d id a s aber-toothed c at l eave o n b ones, i f a ny? A nd w hat a bout u ngulates, w hich h ave b een p ersistently r eported t o c hew o n b ones t o o btain c alcium, p hosphates, o r t race e lements? W ould o ne i magine t hat g iraffes' t ooth m arks o ught t o b e s tudied? I n s hort, t he r esults o f a ctualistic s tudies a re o f l imited, b ut n ot t rivial, v alue. A s I h ave o bserved e lsewhere ( Shipman, 1 981a:360): ..care m ust b e t aken i n i nterpreting t he f ossil r ecord s o t hat t he a ppropriate l evel o f r esolution o f t he r esults i s n ot e xceeded. C onclusions m ust t ake t he f orm, f or e xample, t hat ' this f ossil s hows m arks t hat b est m atch t hose p roduced b y t he g astric j uices o f o wls' r ather t han ' this f ossil w as s wallowed b y a n o wl.' G iven t he c onstraints o f r etrodiction i nherent i n w orking i n a n h istorical s cience, t his i s a n a cceptable a nd, i n f act,

o ptimal l evel o f r esolution.

T his p oint h as b een r eiterated b y m yself a nd o thers w ho h ave b een c areful t o d efine w hat t hey m ean w hen t hey c onclude t hat t heir a ctualistic s tudies r eplicate w hat t hey o bserve i n t he a rchaeological m aterials. W hy, t hen, a re t he r esults o f t hese s tudies r eceived e ither w ith c omplete a cceptance o r w ith d eep s kepticism? A t t he r isk o f o versimplification, I w ill a ttempt t o c haracterize t he a cceptors s keptics i n t erms o f t he i ssues t hat u nderlie t heir p ositions.

a nd

T he a cceptors, I b elieve, f all i nto t wo g roups. T here a re t hose f amiliar w ith t he S EM a nd w ith t he m icrostructure o f t he t ype o f o bject b eing s tudied w ho c an i nspect a nd t houghtfully e valuate t he i mages p ublished o r s hown. I f t heir j udgment a bout t he r esemblances a nd d ifferences b etween t he c ontrols a nd t he u nknowns a grees w ith t hat o f

2 62

t he e xperimenter, t hen s trong a cceptance r esults. T he o ther g roup o f a cceptors a re t hose u nfamiliar w ith t he S EM w ho a re s o i mpressed b y t he e xtraordinary d etail i t c an r eveal t hat t hey u ncritically r egard t he S EM a s a d irect r oute t o t he t ruth. T his g roup u nderestimates t he v ariability w ithin a nd a mong s amples a nd t he s ubjectivity o f t he j udgment t hat t wo i mages a re, o r a re n ot, f undamentally t he s ame. T heir a cceptance r elies o n a c ombination o f f aith a nd t heir f eeling o f b eing u nable t o j udge t he s tudy c ritically. T he s keptics f all i nto t hree g roups.

T he f irst o f t hese a re t hose

w ho a re f amiliar w ith t he S EM a nd t he m icrostructure o f t he o bject s tudied a nd w hose e valuation o f t he r esemblances b etween t he c ontrols a nd t he u nknowns d iffers f rom t hat o f t he e xperimenter. I s uspect t his g roup i s r elatively s mall i n n umbers. T he s econd g roup i s u nfamiliar w ith t he S EM a nd, a t a n i ntuitive l evel, d islikes a nd m istrusts e vidence a rising f rom a t echnology t hat t hey d o n ot u nderstand o r p ossess. T his g roup, i n s um, i s m aking j udgments o n a n e motional, n onrational b asis t hat i s h ighly s imilar t o t he s econd g roup o f a cceptors d escribed a bove. T he t hird g roup i s s keptical b ecause o f t he m ajor, i nherent p roblem w ith a ctualistic s tudies: t he u niverse o f p ossible c auses c an n ever b e f ully k nown. T hey a re u nquestionably c orrect i n t his a ssertion. A ll a ctualistic s tudies c an b e s een a s a rguments b y e limination ( e.g., B inford, 1 981:40, 8 3), w hich a re s tructurally w eak f or t his r eason. A s a r esult, s ome s keptics w ould d iscount a ll a ctualistic s tudies a s i nadequate o r i nsufficient. W hat I t hink h as b een m issed b y t his g roup i s t hat a ctualistic s tudies m ust b e u nderstood i n t he b roader c ontext o f P opperian s cience. I d o n ot b elieve t hat a ctualistic s tudies a re o nly a rguments b y e limination. O ne c ommon s ource o f s kepticism i s a m isunderstanding o f t he i ntent o f t he r esearchers ( or w hat I h ope i s t heir i ntent) i n c oncluding t hat a ncient s pecimen X s hows f eatures t hat m atch t hose o f e xperimental s pecimen Y , w hich w as m odified, p roduced, o r a ffected b y e vent Z . S uch c onclusions a re n ot m eant t o b e d efinitive, u nalterable t ruths t o b e w ritten i n s tone a nd n ever r e-examined t hereafter. S uch c onclusions a re, a t b est, w orking h ypotheses, c arefully f ormulated s tatements o f " greatest s imilarity" f ramed w ithin t he c ontext o f t he e xperimental s ample a vailable t o t hat r esearcher. A nother p oint i s r elevant t o t he i ssue o f a rgument b y e limination; i t i s a m ore c ommon a nd w idely a ccepted p rocedure i n s cience t han i s s ometimes r ealized. B ecause m y t raining i s i n p hysical a nthropology, n ot a rchaeology, t he e xample t hat I t hink b est d emonstrates m y p oint h as t o d o w ith t he i dentification o f s keletal r emains. T axonomy i s c lassically n o m ore a nd n o l ess t han a rgument b y e limination. A n u nknown

i s

s ystematically

c ompared

w ith

t he

a vailable

a nd

r elevant

k nowns i n s earch o f a p oint b y p oint m atching o f f eatures; w hen t his i s f ound, g iven t he l imitations o f t he m aterial a nd i ts p reservation, t he f ossil i s i dentified a s b elonging t o s pecies X . I n r eality, s uch i dentifications d irectly p arallel t hose i n a ctualistic s tudies. T he r esearcher i s, i n f act, s tating t hat h e o r s he f inds t he f eatures o f t he u nknown f ossil m ore s imilar t o t hose o f s pecies X t han t o t hose o f a ny o ther s pecies c onsidered a nd s ufficiently s imilar t o b e a ccepted a s a " match". I f t he u nknown f ossil i s n ot j udged s ufficiently s imilar t o

2 63

a ny o ther k nown s pecies, t hen t he r esearcher c reates a n ew t axon a nd m ust s tate w hat t he d iagnostic a nd d istinctive f eatures o f t hat t axon a re ( i.e., h ow i t c an b e r ecognized f rom o ther s imilar t axa). F requently, a s a g roup o f s pecies b ecomes b etter k nown, t he i nitial d iagnosis m ust b e r evised; s pecies h ave b een k nown t o e merge, s ubmerge, s ink, r ise a gain, s plit a nd j oin a s t he i nitial u nderstanding i s r efined. W hy s hould w e e xpect a d ifferent p attern o f p rogress w ith a ctualistic s tudies? F urther, s ince t axonomy a nd a ctualistic s tudies s hare t he s ame b asic m ethodology o f d efining a nd c omparing r elevant f eatures b etween k nowns a nd u nknowns, a nd s ince i n t axonomy t his a pproach i s s o u niversally a ccepted, c an a ctualistic s tudies b e c riticized o r d iscounted f or u sing a rgument b y e limination? I t s eems t o m e t hat t here i s a g ood r eason f or h ealthy s kepticism a nd c ontroversy a bout t he c onclusions o f a ctualistic s tudies. H ave t he c riteria o r d iagnostic f eatures b een c learly a nd c arefully d efined? A re t hey t he c orrect f eatures? H ave s ome b een i gnored? T here i s l ittle r eason, h owever, f or c ondemning s uch s tudies a p riori, s imply b ecause o f t heir m ethodology . A s econd common m isunderstanding c oncerns w hat h as b een a ccomplished b y r eaching s uch a n o utcome o r c onclusion. I f a s imilarity h as b een e stablished b etween t he e ffects o f a g iven e vent a nd t hose o bserved o n a n u nknown, t he r esearcher h as f ailed t o r efute t he n ull h ypothesis, w hich c an b e g enerally s tated a s: " The e ffects o n t his u nknown s pecimen a re d issimilar i n n ature a nd c ause f rom t hose p roduced o n t his e xperimental s pecimen." T hus, t he k nown e vent m ust s till b e i ncluded i n t he l ist o f p otential e xplanations f or t he o bserved e ffects o n t he u nknown. I f, i n a ddition, a d issimilarity h as b een e stablished b etween t he e ffects o f a k nown e vent a nd t hose o bserved o n a n u nknown, t hen a t l east o ne k nown e vent c an b e e liminated f rom f urther c onsideration. T his i s t he f undamental g eometry o f P opperian s cience: t wo o r m ore a lternative e xplanations ( hypotheses) a re p osed, i mplications o r p redictions a re d erived f rom t hose, a nd t hen n ew d ata a re g athered t o t est t hose p redictions. A s P opper p oints o ut, u sing t his l ogic i t i s i mpossible e ver t o p rove t hat a n h ypothesis i s t rue; i t c an o nly b e p roved t hat a n h ypothesis i s e ither f alse o r n oty et-falsified. N onetheless, o ver t he c ourse o f t ime a nd t hrough c lever a nd r igorous t esting a nd r e-testing o f h ypotheses, i t b egins t o b e c onvincing t hat a n h ypothesis r epeatedly u nable t o b e f alsified i s l ikely t o b e t rue. I n i ts e ssence, o f c ourse, t he P opperian m ethod i s a n a rgument b y e limination. I t i s a lso a pparent t hat a n h ypothesis c an b e u nfalsifiable b ecause i t i s e ither s o v ague o r s o t rivial t hat n o s erious t esting c an b e c onducted, b ut I t rust t hat m ost s cientific r esearchers a re c apable o f r ecognizing a nd d iscounting i nappropriate o r i nsignificant h ypotheses. A s b oth a rgument b y e limination a nd P opperian h ypothesis-testing, a ctualistic s tudies h ave a g reat p otential t o r esolve o r a t l east w hittle

d own a rchaeological p roblems

t o m anageable

s ize.

I f

t he m ost

t hat c an b e s aid o f a s et o f s tudies i s t hat s ome o f t he b lind a lleys a nd f alse h ypotheses h ave b een i dentified a nd t he u niverse o f p otential e xplanations d iminished, c ontribution.

t hen

t hose

2 64

s tudies

h ave

m ade

a s ignificant

F inally,

a s m y w ork c learly s hows,

I b elieve i t i s b oth l egitimate

a nd i mportant t o e xplore t he i mplications o f a n hypothesis t hat h as n ot y et

b een

f alsified.

h ypotheses. n ot

b e

O f

s topped

I n

c ourse, o r

o ther

t he

s talled

w ords,

t esting

o nce

a n

o f

w e

m ust

w ork

a lternative

i nitial

r ound

o n

working

hypotheses

o f

t esting

s hould

h as

b een

c arried o ut. O ne o f t he b est w ays t o g enerate f urther hypotheses t o b e t ested i s t o t ake a n e xplanation t hat r emains potentially t rue a nd t hink,

t alk

a nd

u nderstanding

w rite

o f

s eriously

t he

past

a bout w hat i t w ill m ean t o o ur b roader

i f

t hat

hypothesis

i s

t rue

( remains

u nfalsified). A ctualistic s tudies w ill b e d oomed t o a s terile r ole a s either " spoilers" ( Yellen, 1 977) o r " stamp c ollecting" - t he u nproductive g athering o f e ver-growing p iles o f d ata t hat n ever f lower i nto a pplications o r c onclusions - u nless w e s trive t o s ee t he b roader s ignificance o f o ur t estable hypotheses. Actualistic S tudies I h ave u sing

t he

i nvestigated

S EM.

c utmarks,

T hese

c arnivore

v ascular

g rooves,

i n

d epth

a re:

1 )

f our main a reas o f a ctualistic s tudy

i dentifying

t oothmarks,

w hich

c an b e

r odent

u sed

t o

f or a ltering a particular b one;

2 )

d elayed

w hich

p rocessing

o bjective

o f

t hat

o f

bones,

p rocessing;

3 )

l inear

g rooves,

g nawing,

i dentify

r oot

t he

i ncluding

e tching,

a gent

d istinguishing b etween i mmediate a nd may

b e

r ecognizing

u seful b urnt

i n

bones

d educing

t he

o r

a nd

t eeth

d etermining t he t emperature r ange t o w hich t hey h ave b een h eated, m ay 4 )

h elp

s how w hether

t he

bones

w ere

l ittle

g eneral t erms, C utmarks.

i n

c utmarks d iagnostic t ooth

i dentification

t he

a s

l iterature,

e vidence

c riteria

s cratches

1 981;

S hipman,

e liminate

w ear

o n

b one

t ools,

w hich

c an

b e u seful i f

modified p rior t o u se a nd w hich may i ndicate,

f or

was

l inear g rooves o n bones h as b een m uch

h ominid

b ),

t hat

by

i n

t he

c ontext

a ctivities.

d istinguishing

o ffered

1 981a,

f eatures

o f

o f

p rimarily

P otts

b etween a nd

An

o f

c utmarks

myself

i dentifying

i nitial

( Potts

a nd

a nd

t o

1 984),

i nclude

a nd R ose,

s et

o f

c arnivore

a nd

S hipman,

w ith s ubsequent r efining o f t hose c riteria t o w ere

n ot

t ruly

d iagnostic

( Shipman,

1 983),

d istinguish more c learly b etween c utmarks a nd v ascular g rooves a nd R ose,

i n

t he u se t o which t hose b ones w ere p ut.

T he

d iscussed

w hich

h eating o ccurred i n n atural o r manmade f ire;

r ecognizing u tilization

t he

a nd

r esponsible

t o

( Shipman

a nd t o d ocument m ore f ully t he variability i n c utmarks a b etter

d escription o f

r odent

g nawing marks

( Shipman

1 983).

W ork b y o thers h as s hown t hat t he i ssue o f r ecognizing c utmarks i s m ore

c omplex

t han

B ehrensmeyer e t a l.

I

i nitially

( 1986),

O liver

t hought. ( 1984),

s hown t hat t rampling o f b ones o n s andy o r, m ay

p roduce

marks

t horough

t reatment

( 1985).

S everal

s tudies ( Olsen

a nd a nd

c utmarks

i n

t hat o f

a n

s ome

t rampling

a spects

S hipman,

t o o f

p ress)

( trampling m arks)

marks

i s

a nd

e specially, mimic f ound

C ook

( 1984)

r ocky s ubstrates

c utmarks. i n

( 1985), h ave a ll

Andrews

T he

m ost

a nd

C ook

t he t rampled a ssemblages r eported i n t hese

e xtensive i n

e xtent

A ndrews

a nd F iorillo

s et

o f

e xperiments

c arried

o ut

r ecently

a re i mportant f or d istinguishing p seudo-

f rom g enuine o nes.

2 65

F irst,

t he

r eported

i ncidence

o f

marked

b ones

i n

t rampled

a ssemblages i s v ery h igh. F or e xample, A ndrews a nd C ook ( 1985:682) f ound 7 0% o f t he b one b ore marks a nd O liver ( 1984:27) o bserved t hat t rampling marks " ...are s o q uantify t heir o ccurrence."

n umerous t hat n o a ttempt w as made t o O lsen a nd I h ave m ade s imilar f indings i n

a n i ndependent s tudy o f various b one a ssemblages t rampled u nder a w ide r ange o f c ircumstances ( Olsen a nd S hipman, i n p ress). S ince n o a ssemblage o f b ones o f c utmarked b ones a ttempting T rampled

I n

( see

i s F ig.

r eport

5 10

c ontrast,

r arely

i dentify

bone

g rooves C ook

t o

s how

k nown t o h ave ( Bunn, 1 982), c utmarks

o n

a

h eavily

c ommonly

h eavily

marked,

3 a,

A ndrews

a nd

marks

bones

s uch

b een b utchered h as m ore n o a nalyst s hould f eel

b i n o n

1 1 b ones,

t hat

h ave

a reas

s een

b een

e xtensive marking;

o f

o ccurs

e xtensive

a ctivities

t hat a

i ndividual

bones

f orms

h ominids,

g enuinely

i s

more

h as

a ttachment,

a bundant

o r

a nd

t o

t o

e specially b een

t han

h ominids

s trip m eat

t endon

b earing

h ave

a brasion

b y

I would e stimate

T he o nly e xception w hich

r emove

c utmarks,

l ikely

l inear

A ndrews

p rocessed

b een made

a ssemblage

s edimentary

1 985:681);

i n my e xperience,

a ttempt

h eavily-marked o f

s craping

many

marks.

h eavily-marked

t rampled

b utchered

f rom

o r p eriosteum,

o r

o r

e xposed

t o

processed

by

a ll o ther t hings b eing e qual.

S econd, mark

a n

m uscle

l eave

C ertainly o ther

w hen

a ssemblage.

multiple

o r a n a verage o f 4 6 marks p er b one.

t hat most bones s how 1 -6 i ndividual c utmarks. I have

marked

b earing

C ook,

t han 2 0-25% c omfortable

t he

most

c ommonly m imicked

( Potts a nd S hipman,

t ype

o f

c utmark

i s

a s craping

1 981:577),

..formed b y d rawing a n e dge a cross a bone s urface i n a d irection r oughly p erpendicular r esults a rea o f

t o

t he

l ong

a xis o f t he e dge.

i n multiple, f ine, parallel s triations bone r ather t han c onfined t o a s ingle,

T his a ction

a cross a b road e longated m ain

g roove.... I w ould n ew a dd t o t his d escription t hat t he b road a rea b earing s triations i s d epressed b elow t he u naltered s urface o f t he b one. I n a ddition,

s ome s craping marks s how perpendicular c hattermarks t hat h ave

n ot

o bserved

b een

i n

t rampled

b ones

( Olsen

a nd

S hipman,

i n

p ress).

T his n ew c riterion s hould h elp d istinguish s craping marks f rom t hose p roduced b y many s mall, i ndividual particles o f s and o r r ock w hich may l eave parallel s triations b ut w hich g enerally w ill n ot r emove s urface b one o ver a b road a rea. C aution must b e o bserved, h owever, a nd a ssemblages d etermine

w ith

whether

many t hose

s craping marks

marks

a re

m ust

c utmarks

b e

c losely

( produced

i nspected by

t ools)

t o o r

e ffects o f various t ypes o f s edimentary a brasion. T hird, m ust b e

s edimentary c ontext i s a n i mportant f actor a nd more c aution

e xercised

s ubstrates

t han

d ata s uggest t hat c utmark m imics. e rectus K enya.

i n

i nterpreting

t hose

f ound

i n

a ssemblages

f ine

f ound

s ediments.

M y

i n

r ocky o r

own

f ine, s ilty s ubstrates t hemselves d o T his c onclusion i s s upported by t he

b oy's

s keleton

f rom

T hat

s keleton

w as

N ariokotome, r ecovered

s ediments a nd was a lmost c ertainly t rampled:

2 66

w est

f rom

o f

f ine,

L ake s ilty,

s andy

e xperimental n ot p roduce f amous H omo T urkana,

i n

l acustrine

T he

t op

o f

t he

b ioturbation

f ossiliferous

[ including

h orizon

h ippo

s hows

f ootprints]

m any

a nd

s igns

s everal

o f

o f

t he

b ones w ere f ound b roken o r l ying i n positions s uggesting t hey h ad b een t rampled b y l arge mammals. N onetheless, f rom

n one

t rampling

o f

t he bones

( Walker,

( Brown e t a l.,

s how

p ers.

a ny

s igns

c omm .),

1 985:788).

o f

s edimentary

s uggesting

t hat

a brasion t he

f ine

o f bones

f ound

s ediments p erhaps c ould n ot p roduce obvious l inear g rooves. I t i n

i s

f ine

d ifficult

s ubstrates

t o k now

t he

a ccompanied

a ppropriate

by

s tone

t reatment

t ools.

T he

t ools

t hemselves

m ay o r may n ot h ave b een a part o f t he s ubstrate a t t he t ime o f a ny h ypothesized t rampling. P erhaps t he best a pproach i s t o c onsider a s much e vidence a s i s a vailable, i ncluding i nformation a bout t he w eathering m ight

s tage

i ndicate

a nd p resence h ow

r apidly

o r

a bsence

t he

bones

o f

r odent

b ecame

g nawing marks

b uried

a nd

t hat

w ere

t hus

r emoved f rom t he d angers o f t rampling.

t hey

F ourth,

t he

a re

t o

d ue

orientation

a nd

l ocation

o f

marks

t rampling o r hominid a ctivities.

by s everal r esearchers t hat s hafts t han n ear j oints.

may

i ndicates P rolonged

h ominid b utchery was D rift, w ith a h ighly

b iased r epresentation o f s keletal e lements. M ost o f t he P rolonged D rift a ssemblage a re n ear-joint, b ut s o p reserved

e lements s hort

f rom

s haft

s trong

S hipman,

s ite

f ragments

a ssemblage, a

( Gifford

t his

N gamuriak,

1 986b).

e t

a l.,

a re

1 981).

r emarkable

a ttached

t o

t he

I n i n

a rticular

o f

T hus

n ear-joint

i t

s eems

l ikely

s till b e s tatistically d ifferent. ( 1985:682-684)

t ransverse margins. o riented

marks,

t hat more t o

t he

t hat

t o

c utmarks

a t

o f

( Shipman,

7 0%

h ave

o f

o n

i n

t he

a xis,

been

1 986a,

c arnivores,

b ; a nd

a lthough t he f requencies m ay t rampling

Andrews a nd

m arks

a re

o ften

I ,

c utmarks

i ntent

O lduvai, o n

l ong

a nd

s kill.

w here

bones

B ut,

I have

i n

d ocumented

a re o riented oblique

i t c an b e c oncluded t hat t hese a re r elatively

c aused by

B ed

I

f lakes,

t he

t ool

1 986b).

t heir

B ed

t hese

marks a s c utmarks,

t hat

v ery

b iased

d oes n ot s how

( Marshall,

h ominids,

a nd

A l ess

a xis o f l ong bones a nd o blique t o t he s capular h ominids might produce s imilarly p laced a nd

t hose

l ong

i dentifiable f ew

I n t erms o f o rientation,

s hown

d epending

l ike

t han

bone's

u nlikely n umber

h ave

t o t he l ong O f c ourse,

c ircumstances

t he

v ery

e nds.

c utmarks

t rampling a ll p roduce m any m idshaft marks, Cook

f act,

h aving

t he c utmarks o n a re most o f t he

t hat was a lso c ertainly butchered,

predominance

whether

t rampling marks o ccur more f requently o n U nfortunately, my s uggestion t hat a

predominance o f n ear-joint c utmarks based o n a nalysis o f a n a ssemblage,

bones

r eveal

I t h as b een observed

s ites

t rampling. i s

t ype

F urther,

s ignificantly most

l ikely

t o

t he

f requency o f

c orrelated h ave

l eft

w ith

t he

c utmarks

T his f inding s trengthens t he i nterpretation o f t hese s ince t here i s n o r eadily d iscernable r eason w hy t he

f requency o f t rampling m arks s hould be c orrelated w ith t he f requency o f a ny p articular t ool t ype. Another p ossible s ource o f c utmark m imics was p resented a t t he S EM C onference b y F riederman S chrenk,

w ho s howed h yena t ooth s cratches t hat

i ncluded f ine l inear s triations w ithin t he main g roove. h ave

e ach

l ooked

a t

b ones

c hewed

by

2 67

s potted

a nd

S ince h e a nd I

s triped

h yenas,

a nd

s ince h e h as s een s triations f requently a nd I h ave n ever o bserved t hem, t his

p roblem

d iscover

o bviously

d istinctive

c alls

f or

f eatures

u sed t o i dentify t hem r eliably. s een

o nly

m imics.

a f ew I c an

t oothmarks r epeated

marks),

i n

I f

t he

s triated

e ffort.

W e

t oothmarks

h ope

t hat

t hat

t hey a re

n ot

c lose

s ame

marks

t his

p erhaps

s pot,

t hat

t hese

s imilar

s how

f ine

o ught

t o

b e

m arks

t o t hen

r aised,

w ere

r odent

s triations

h ypothesis i s c orrect,

s triations

s ee

e dge

h ow

e ffect

t he

t hat

w ould produce

n ormal

w ithout

h aving c utmark

c aused

g nawing

( see

t ooth

s uch

n ot

s triations.

morphology

r epeated g nawing.

o f

h yenas

by

w hich

S hipman

a nd

( like r odent g nawing i ncised.

S econd,

p erhaps t he h yena producing t hese marks h ad broken o ff a t ooth, a r ough

t o

c an b e

I t i s m y s ubjective i mpression,

briefly,

F irst,

t he

p roduces

1 983).

h is

a t present t wo h ypotheses a bout h ow s uch s triated

produced.

g nawing

f requently R ose,

m icrographs

o ffer

a re

a c ollaborative

o f

O therwise, c ould

l eaving I c annot

produce

T ooth b reakage must

b e

s uch

a n

a r elatively

i nfrequent o ccurrence, c onsidering t he n umber o f t imes a w ild c arnivore c hews a nd d oes n ot b reak i ts t eeth. A lthough

t he

c omplexities u sefulness

f oregoing

a nd o f

paragraphs

c autions

d ata

o f

a bout

h ave

i dentifying

which

bones

f ocused

o n

c utmarks,

w ere

t he

t he

a ctually

g rowing

potential

p rocessed

by

h ominids i s s o g reat t hat I b elieve i t i s w orth p ersisting i n t rying t o r efine

t he

m ethodology

s ignificant

t ypes

o f

t o

e nhance

a nalyses

t hat

i ts

c ertainty .

c an

b e p erformed,

T here

a re

o nce

s everal

a s ample o f

c utmarked bones h as b een i solated. F irst, provides

a nd

most

a c ausal

h ominids.

M any

n ecessary

t o

a ssociated

obviously,

a nd

t emporal

s ites

f ind

b ones

h ave

s olid a nd

p resence

b etween

c omplex

e vidence

s tone

t he

l ink

o f

b ones,

t aphonomic

c utmarked s tone

b ones

t ools,

h istories,

s o

i t

a nd i s

f or t he i nterpretation t hat s patially

t ools

w ere

d eposited

a t

t he

s ame

t ime by

h ominids. S econd, c utmarked?)

t he a nd

patterns s pecies

may r eveal a g reat d eal. c utmarks t he

o n

b ones

s ome

i n

N onetheless,

bones

t he

o f

r epresentation ( which

( which bones

s pecies

a re

a re

c utmarked?)

I w ould h esitate t o j ump f rom t he p resence o f i n

a n

a ssemblage

a nalyzing

s keletal

r epresentation

o nly

a ssemblage w ere

t he

t o

t he

c onclusion

t hat a ll o f

c ollected o r p rocessed by h ominids.

c utmarked

s ubset o f a n a ssemblage w ill

e nable t he a nalyst t o a nswer q uestions l ike: d id s ystematic b utchery, i .e., a h ighly patterned, r epetitive p rocessing o f c arcasses, o ccur? a re

c utmarks

c oncentrated

s uggesting m eat i n

l ocations

was

s pecies

d oes

mortality

o n

f ocus

s uggestive

b utchered t he

t he

o f

r estricted p rofile

b ones

t hat

b ear

l arge

o f t he p rocessing? s kin, t o

s ome

o f

t he

t endon

o r

f at

s ize

r ange

o r

b utchered

m uscle

masses,

o r d o c utmarks o ccur h arvesting? s ome

s pecies

a re

habitat l ook

t ype?

l ike

a

c atastrophic o r a ttritional a ssemblage? Third,

a dditional

i nformation

m ay

b e

d erived

f rom

c areful

i nspection o f t he c utmarks t hemselves. B romage a nd B oyde ( 1984) h ave s hown t hat d irectionality c an s ometimes b e i nferred f rom c utmark morphology. T his i nformation c ould p otentially b e u sed t o d etermine w hen

h andedness

o ccurred

a nd

t he

( Shipman a nd R ose,

a ccompanying 1 983).

2 68

l ateralization

o f

t he

b rain

T ime o f p rocessing.

A nother a spect o f s tudying c utmarks t hemselves m ay

p rove h ighly u seful; c utmark m orphology c an r eveal t he t iming o f t he p rocessing o f a c arcass r elative t o t he d eath o f t he a nimal i nvolved. I n a c ollaborative e ffort ( Russell e t a l., 1 985), R ussell, V illa a nd I h ave s hown t hat w e c an m orphology o f t he m arks,

d istinguish, o n t he b asis o f m icroscopic b etween i mmediate a nd d elayed p rocessing o f

c arcasses.

p rocessing

B y

i mmediate

w e

m ean

p rocessing

o f

a c arcass

w hich o ccurs a t o r s hortly a fter d eath, w hen t he f lesh i s s till a v iable s ource o f f ood. I n c ontrast, d elayed p rocessing o ccurs l ater i n t ime, a fter t he f lesh i s d ried o r d ecayed. I t s eems l ikely t hat t he t ime p eriod i ntervening b etween i mmediate a nd d elayed p rocessing w ill b e m ore d ifficult t o r ecognize. T able 1 s hows t he t ypes o f a ctivities t hat m ight b e e xpected t o o ccur i n e ach t ype o f p rocessing; i t i s i mportant t hat t he o bjectives a re d ifferent i n i mmediate a nd d elayed p rocessing b ecause d ifferent r esources h ave d ifferent t emporal l ives. I t i s a lso s ignificant w hether t he s ubject o f t he p rocessing i s h uman o r n onhuman, s ince t he f ormer r aises t he p rospect o f e ither c annibalism ( immediate p rocessing) o r s econdary b urial ( delayed p rocessing), b oth o f w hich h ave i nteresting i mplications f or u nderstanding t he s ystem o f b eliefs o f a g roup. T his a pproach h as b een a pplied t o t he N eolithic a ssemblage f rom F ontbregoua, F rance, i n w hich b oth h uman a nd n onhuman r emains s how c utmarks i n s imilar p laces ( see V illa e t a l., 1 986, f or a m ore e xtensive d iscussion). T his w ork c onstituted a t est o f t he h ypothesis t hat d ietary c annibalism ( i.e., e ating h uman r emains) w as i nvolved; b y e stablishing t hat b oth t he h uman a nd f aunal m aterials w ere s ubjected t o i mmediate p rocessing, t he h ypothesis w as s upported. M ethodologically,

t he p roblem o f

d istinguishing b etween i mmediate

a nd d elayed p rocessing d epends u pon t wo f actors: t he a ge ( state o f w eathering) o f t he b one s urface a nd t he a ge o f t he c utmark. F igure I s hows f our t heoretical c ombinations o f b one a ge a nd m ark a ge, a lthough o ne c ombination ( fresh b one, o ld m ark) c annot a ctually e xist. I n o ur e xperiments, R ussell i ndependently p repared a s eries o f r eplicas o f s licing m arks o n b ones ( N=8 s pecimens) t hat r epresented t hree s tates: f resh m arks o n f resh b one; o ld m arks o n o ld b one; a nd f resh m arks o n o ld b one. O ne s pecimen w as a n a ged b one b earing o ld m arks o ver w hich R ussell c reated a n ew g eneration o f m arks. T hese r eplicas w ere a ssigned l etter c odes a nd s ent t o m e w ithout f urther d ata. M y d iagnoses o f t hese s pecimens w as 1 00% a ccurate. A lthough t his i s a s mall s ample s ize, t he r esults a re m odestly i mpressive. S ince e ach r eplica c ould h ave b orne a ny o f t hree s tates, t he p robability o f i dentifying a ll o f t he s pecimens a ccurately b y c hance w ere 6 561:1. S ome a dditional s tudies h ave b een c arried o ut s ince t hen, b ut m ore a re s till n eeded t o e xplore t he r ange o f v ariability i n m ark m orphology a nd t o c onfirm t hese i nitial r esults.

2 69

O ld cut

O ld cut

F resh bone

O ld bone

A

A

F resh cut

F resh cut

F resh bone

O ld bone

BO N E

SU R F A C E

AG E

F ig. 1 . T heoretical m odel o f t he d ifferent c ombinations o f c utmark a nd b one a ge r esulting f rom c arcass-processing. N ote t hat t he a lternative i n t he u pper l eft ( old c ut, f resh b one) c annot a ctually o ccur.

2 70

TABLE 1 .

S ome o f t he b ehaviors a nd o bjectives a ssociated w ith

i mmediate a nd d elayed c arcass-processing. S ubject

T iming

B ehavior

Objective

A nimal

I mmediate

H unting

Obtain m eat,

marrow,

f at

E arly s cavenging

O btain m eat,

marrow,

f at

M anufacture

Obtain s kin,

t endon,

b one

C onsumption

Obtain m eat,

marrow,

f at

L ate s cavenging

O btain marrow

M arrowing

Obtain marrow

? Manufacture

Obtain s kin,

t endon,

b one

R itual c annibalism

Appease gods

D ietary c annibalism

Obtain meat,

marrow,

f at

S calping

O btain t rophy

M utilation

Obtain t rophy,

S acrifice

Appease gods

S econdary b urial

F inish burial r itual

C emetery r elocation

Facilitate t ransport

D elayed

H uman

I mmediate

D elayed

t wo

A t p resent, t he f ollowing d escriptions s erve t o c haracterize t he s tates. I mmediate p rocessing i s c haracterized by f resh, i ntact

b one

s urfaces

m arks

a re

w ith

s triations

c ut

o blique

F resh

n ormal

e longate,

d istinguishable a nd

v engeance

i nto i n

When a nd a ged, l ines

o f

a b one

( Bromage

( Fig.

f ine 2 a,

s ubjected

s tructural

n ormal

f or

c rack

d evelopment.

f loor.

a nd

t o

B oyde,

i mmediate

a s ingle

s mears, 1 984)

a re

T hese

parallel n adir

i s

oblique

f aulting

o ften

v isible.

i s

p rocessing

b ecomes

w eathered

T he b one s urface d evelops c racks a long S ince

o rganization I t

O ften,

B one

f ine,

b ).

w eakness.

s tructural

multiple

d etail t hat i s d istinctly d ifferent f rom

t hese f eatures a lter.

t he

a nd

b earing s licing marks.

w ith

s licing marks.

s how m uch

n ormal bone t exture

g rooves

t heir w alls s uch

c hipping

c utmarks

u ltrastructure

l inear

t he

o f

p ossible

2 71

c utmark

t he

bone,

t hat

t he

i tself i t

h as

s erves

i mmediate

d isrupted

a s

a f ocus

a rea o f t he

-a

F ig. 2 . E xperimental s tudies o f d elayed a nd i mmediate p rocessing. a ) F resh c utmarks o n a f resh b one w ith a n i ntact s urface. b ) A c lose-up o f t he s ame s licing m arks, s howing t he f ine s triations, b one s mears a nd o blique c hipping c haracteristic o f f resh s licing m arks. c ) A s eries o f i ntersecting, o ld s licing m arks, o riginally m ade o n f resh b one t hat i s n ow w eathered a nd o ld. N ote t he n etwork o f w eathering c racks b oth w ithin a nd w ithout t he c utmarks. d ) A c lose-up o f t he s ame s et o f m arks. N ote t he l oss o f d etail w ithin t he c utmarks a nd t he d evelopment o f f ine l ongitudinal a nd p erpendicular c racks w ithin e ach m ark.

2 72

c utmarks n ot y et

d evelops c ertain.

c racks e arlier t han a djacent a reas, t hough t his i s C racks f requently d evelop a long t he n adir o f t he

s licing m ark; i n a ddition, a s eries o f s hort c racks m ay d evelop a long t he w alls o f t he m ark. T hese c racks o ften h ave t wo i ntersecting a rms, o ne p arallel t o a nd o ne p erpendicular t o t he m ark 's l ong a xis. I n o ur s ample, s uch c racks d o n ot e xtend o utside t he m ark i tself, a lthough l arger s cale c racks p arallel t o t he p redominant f iber o rientation o f t he b one s urface m ay i ntersect a nd c ross t he s licing m ark. A lthough t he f ine s triations r emain v isible i nside t he m ain g roove, t hey b ecome m uch m ore d ifficult t o i dentify a s t hey h ave l ost b oth d etail a nd d epth. A s a r esult, t hey a re o ften v isible o nly w hen t he s pecimen i s h ighly t ilted ( angles o f c lose t o 4 5 ''t o t he s urface) a nd w ith a h igh c ontrast i mage ( Fig. 2 c, d ). Delayed T ypically, i n

processing p resents a d ifferent s et d elayed p rocessing t he b one s urface i s

o f f eatures. w eathered a nd

c racked. W ork b y B ehrensmeyer ( 1978) a nd G ifford ( 1977) h as s hown t hat w eathering b egins a t a bout 6 m onths t o o ne y ear a fter d eath, d epending u pon m icroenvironment a nd c limate. H owever, b ecause t he s licing m ark i tself i s m ade a ppears f resh.

a fter w eathering a nd c racking h as o ccurred, t he m ark I t p ossesses a ll t he d etail, d epth, a nd h ighly v isible

s triations f ound i n f resh m arks o n f resh b one. T hus, i t i s t he d ifference i n w eathering s tate b etween t he o utermost b one s urface a nd t he c utmark t hat i dentifies d elayed p rocessing. C utmarks r esulting from

d elayed

p rocessing

h ave

n o

r egular

r elationship

t o

c rack

o rientation; a pparently c racks h ave n ot y et h ad t ime t o d evelop w ithin f resh m arks. T he d istinction b etween a n o ld m ark a nd a n ew m ark o n t he s ame w eathered b one ( Fig. 3 a, b ) i s s triking. B urnt b ones a nd t eeth. T he s ummary o f t his w ork p resented h ere i s d rawn f rom S hipman e t a l. ( 1984b), w hich s hould b e c onsulted f or m ore e xtensive i nformation a bout m ethodology a nd r esults. B ased o n c ontrolled h eating i n a m uffle f urnace, m anually c leaned s heep a nd g oat m andibles ( bearing t eeth) a nd a stragali s how a s eries o f c hanges i n c olor, m icroscopic m orphology, a nd c rystal s tructure. D ocumenting c hanges p ermits t he a nalyst t o d educe t he r ange o f t emperatures t o w hich t he s keletal e lement i tself h as b een h eated. I t i s i mportant t o r ealize t hat t he maximum t emperature r eached b y t he b one o r t ooth r epresents t he m inimum t emperature o f t he h eating d evice ( fire, p yre, h eating o ven, e tc.). I n o ther w ords, t he h eating d evice w as a t l east a s h ot a s t he b ones o r t ooth h eated i n t hat d evice. H owever, v arious c ircumstances, s uch a s t he e xtent o f f leshy c overing o f t he b ones, m ay p rotect t hem f rom r eaching a s h igh a t emperature a s t he h eating d evice i tself r eaches. T he

c hanges

i n

m icroscopic

m orphology

t hat

a ccompany

h eating t o

d ifferent t emperatures c an b e d ivided i nto f ive s tages, w hether t he t issue m onitored i s b one, d entin o r e namel. A ll t hree t issues s how a nalogous c hanges i n m orphology t hat w e h ave a ttributed t o, f irst, t he b reakdown o f t he n onmineral c omponent o f b one o r t ooth a nd, s econd, t o c hanges i n t he h ydroxyapatite c omponent o f t hose t issues. F igures 4 -6 ( reproduced f rom S hipman e t a l., 1 984b:315-318) s how t hese s tages, w hich c an b e d escribed i n g eneral t erms a s f ollows:

2 73

. 4 4 4 .

r o ) W —I a g 4 : — ,2 1

4 )i P W , Z

a ) 4 ) 0 4 4 0 0

4 )

U

r 0 $ i ( 1 ) P

> 4 •

r ö

o l d b o n e . c a n l o w e r

c l ) t n 01 0 •

C l

r n 4 1

U

F = C

I -)

n z ,

t o v a s c u l a r

c u t m a r k s o n

1 3 1

H c a

c r a

V)L P 0

r t j 0

1 4 - e

4

0

0 ' 1 C J c u

t l

2 74

0

r t l

U

4 -) C / ]

0

a )

0

I

— 4 /

, 3 4

P U ( 1 ) 4 1

O

i

P u N . 4 U 0 1 -w0 0 0 u ] • g ) . 4 r ' t J g l

•— 4 a ) C T 3 1 ) r o

• r i

z n

t 4 ( 1 )

Ero c 0

> 4

0

A .• H

I 0 t n r C 3

I

r i

Q )

, -

( 1 ) 4 . J c d

• 0 a r i W

, z

c u s t i ]

0 °

U

j 2i0 b C 1

Q . 1

c i 2

" 1 0 › . 4

4 1 0 1-Q U 0 0 0 4 1 4 1 4 4

C 1

P

( 1) )

4 -) $ 4 C , 4 1

C f )

0

4

0 r e

E 0 1 ) C d

A

Fig.

4 .

M icroscopic

m orphological

s tages

n atural d entin s urface o f t he pulp c avity. b ) V ,

S tage

I I.

c )

S tage

I II.

d )

s hown a t h igher magnification.

S hipman e t a l.,

1 984b,

J . Arch.

p roduced a )

S tage I V.

by

S tage I , e )

h eating

o n

a

n ormal d entin.

S tage V .

f )

S tage

( Plate r eproduced by p ermission f rom

S ci.,

2 75

A cademic P ress.)

F ig. 5 . M icroscopic m orphological s tages p roduced b y h eating o n n atural, n onocclusal, e namel s urfaces. a ) S tage I , n ormal e namel. b ) S tage I I. c ) S tage I II. d ) S tage I V. e ) S tage V . ( Plate r eproduced b y p ermission f rom S hipman e t a l., 1 984b, J . A rch. S ci., A cademic P ress.)

2 76

n i ntact F ig. 6 . M icroscopic m orphological s tages p roduced b y h eating o S tage I I, b one s urfaces. a ) S tage I , n ormal s ubchondral b one. b ) s ubchondral b one. c ) S tage I II, s ubchondral b one. d ) S tage I V, S t a g e V , s ubchondral b one. e ) S tage V , s ubchondral b one. f ) ortical s ubchondral b one s hown a t h igher magnification. g ) S tage V, c 984b, J . b one. ( Plate r eproduced b y p ermission f rom S hipman e t a l., 1 A rch.

S ci., A cademic P ress.)

2 77

..in S tage I ( 20-

-I — I

04 r - i r I ZI 0

( / )

•, - I

0

` 1 4 51 z l i i

r

0 10

• i 4 3

0 r d 1 . , w g • , i 0 W a i c n c i _ 4 4 0 U C < 4 • , -1 U t 3' t : 3 1 4 a i ' . . . 4 , . ) U ( 1 : • -- g 04 w 4 -) U co g c n . > I g i 0 U ) U ) 4 J t i j 0 , • W gl ( 1 3 , .O 0 .2 .( , 1 _ ) 1 2

g ,

U ). 4 Ja„4 _ ,0 W

n j W r j ) c o

R I

g

e l ö g i U

0

4 1 , 4

54 . ,,, › ,

0

0

r d e n — I r d -P C i t 4 . J W t n , Z

. 1 : 1 U ) • g • , I re c f )

2

n i . a .

E

W r n w 0 . 4 —1 • , I -. 4) ( " r i, t : P E l ( I S . . . . 2 ( 0 w 0 0 r t l 3 L i i 1 r n

g i

• . IL : j W E

3 11

W , 4 4 J

e n 1 : 1 0 4 ( 1 ) M g i 3 4 -) ra 0 0 0 0 4) . 1. Z >I t n r I ( 1 . ) U l " L I C d

' — I • , 1 r C I . i • , 1 g 0 U G g >

4 1

w

0

0 , 9 ( 1)

r 1 4 ( U D 2

al

' ( 1 T ' 3 :1

>

U )

. 1

0

° t n n i

• t : 31 C • , 4 W 1 1

2

. . r n 1 l