Natural Formation Processes and the Archaeological Record 9780860544555, 9781407346267

Table of contents :
Front Cover
Copyright
Table of Contents
CONTRIBUTORS
PREFACE
RE-FORMING ARCHAEOLOGY: A FOREWORD TO NATURAL FORMATION PROCESSES AND THE ARCHAEOLOGICAL RECORD
DETERIORATION OF ADOBE STRUCTURES: A CASE STUDY FROM SAN PEDRO DE ATACAMA, NORTHERN CHILE
NATURAL FORMATION PROCESSES AND SNOW-BASED SITES: EXAMPLES FROM ARCTIC CANADA
RADIOCARBON REVERSALS AND STRATIGRAPHIC DISCONTINUITIES: THE EFFECTS OF NATURAL FORMATION PROCESSES ON COASTAL CALIFORNIA ARCHAEOLOGICAL SITES
THE PLACE OF THE STUDY OF SITE FORMATION PROCESSES IN PREHISTORIC RESEARCH IN INDIA
EXPERIMENTALLY-DERIVED CRITERIA FOR ASSESSING HYDROLOGIC DISTURBANCE OF ARCHAEOLOGICAL SITES
THE IMPACT OF FLUVIAL PROCESSES ON EXPERIMENTAL SITES
DISTINGUISHING NATURAL FROM CULTURAL SALMONID DEPOSITS IN THE PACIFIC NORTHWEST OF NORTH AMERICA
NATURAL FORMATION PROCESS EXPERIMENTATION AND ARCHAEOLOGICAL ANALYSIS
NATURAL FORMATION PROCESSES AND THE ARCHAEOLOGICAL RECORD: PRESENT PROBLEMS AND FUTURE REQUISITES

Citation preview

Natural Formation Processes and the Archaeological Record

edited by

D. T. Nash and M. D. Petraglia

BAR International Series 352 1987

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 -S352, 1987: 'Natural Formation Processes and the Archaeological Record' © The Ind ivid ual Authors, 1987 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 9780860544555 paperback ISBN 9781407346267 e-book DOI https://doi.org/10.30861/9780860544555 A catalogue record for this book is available from the British Library This book is available at www.barpublishing.com

CONTENTS

C ontributors

i v

P reface F EKRI A . HASSAN R e-Forming A rchaeology: A Foreword to Nat ur al For m a ti o n Pr o ce s se s an d th e Archaeological Record

1

MICHAEL B . SCHIFFER, ANA MARIA BARON, PAULINA PAUCHARD CORTES and JAVIER TAMBLAY SEPULVEDA Deterioration of Adobe Structures: A Case Study fr o m Sa n Pe dr o de At a c a m a, No r t h e r n Chile

1 0

JAMES M . SAVELLE N atural Formation P rocesses Snow-Based S ites: Examples from Arctic Canada

3 0

and

JON M. ERL ANDS ON and THO M AS K . ROCK WELL Radi o c ar b o n Re v er s al s an d Str atigr aphic Discontinuities: the Effects of Natural Formation P rocesses on Coastal California Archaeological S ites

5 1

K . PADDAYYA The Place of the Study of Site Formation P rocesses i n P rehistoric Research in I ndia

7 4

KATHY D . SCHICK for Assessi ng Archaeological

86

Experi mentally-Derived Criteria Hydr ol ogic Distur bance of Sites

MICHAEL D . P ETRAGLIA and DAVID T . NASH The of Fluvial P rocesses on Experi mental Sites

Impact 1 08

VIRGINIA L . BUTLER Distinguishing Natural from Cultural S almonid Deposits i n t he P acific Northwest o f Nor th Am erica

131

LUANN WANDSNIDER Natural For mation Process Experimentation and Archaeological Analysis

1 50

DAVID T . NASH and MICHAEL D . PETRAGLIA Natural F ormation P rocesses and the Archaeological R ecord: P resent P roblems and Future Requisites

1 86

i ii

CONTRIBUTORS

Ana Maria Baron, S antiago, C HILE Virginia

L .

P ehuen

Butler,

7 280,

dep.

Department

U niversity o f Washington,

S eattle,

1 00,

of

Las

C ondes,

Anthropology,

Washington

9 8195 U SA

J on M . E rlandson, D epartment o f Anthropology, U niversity o f C alifornia, S anta B arbara, C alifornia 9 3106 U SA F ekri A . H assan, D epartment o f Anthropology, Washington S tate U niversity, P ullman, Washington 9 9164 U SA David T . N ash, D epartment o f Anthropology, U niversity o f N ew Mexico, A lbuquerque, N ew Mexico 8 7121 U SA K . Paddayya, Department of Archaeology, Deccan College, P oona- 4 11006 I NDIA Paulina P auchard S antiago, C HILE

Cortds,

Rafael

Canas

2 46,

3 er

piso,

Michael D . Pet r agl i a , Department of Anthropology, U niversity o f N ew M exico, A lbuquerque, N ew M exico 8 7121 U SA Thomas K . Rockwell, Department of G eology, San S tate U niversity, S an D iego, C alifornia 9 2182 U SA

Diego

James M . Savelle, Scott Polar Research Institute, U niversity o f C ambridge, C ambridge CB2 l ER ENGLAND Kathy Schick, Department of Anthropology, U niversity, B loomington, I ndiana 4 7405 USA

Indiana

Michael B . Schiffer, Department of Anthropology, U niversity o f A rizona, T ucson, A rizona 8 5721 U SA Javier Tamblay S epulveda, C ondes, S antiago, C HILE

P ehuen

7 280,

dep.

1 00,

Las

L uAnn Wandsnider, D epartment o f Anthropology, U niversity o f N ew Mexico, A lbuquerque, N ew Mexico 8 7121 U SA

i v

PREFACE The papers i n this volume, with t he e xception of t hose written by S chiffer et a l. and P addayya were p resented at a symposium entitled " Natural Disturbance P rocesses and t he A rchaeological R ecord". The symposium was held at the 5 1st annual meeting o f t he Society f or American A rchaeology, i n N ew O rleans, L ouisiana, o n April 2 7, 1 986. Most o f these papers have s ince been r evised a nd u pdated f or i nclusion i n t his volume. For this volume, we have opted to change the symposium t itle f rom " Natural Disturbance P rocesses" to " Natural Formation P rocesses". For s ome a rchaeologists t he t erm " disturbance" s eems to possess a value-laden meaning which acts as a barrier t owards p roductively i nvestigating t he a rchaeological r ecord. Our belief i s t hat " disturbance" i s a u seful concept as l ong as i t i s v iewed i n context with the overall f ormation o f the a rchaeological r ecord and not u sed to d ismiss s ites o r p arts o f s ites. T he t erm d isturbance should be used to denote any process which alters the position or a rrangement o f materials. I n r egards t o t he s tate o f t he r ecord, a ll d isturbance p rocesses a re natural f ormation p rocesses. But, a ll n atural f ormation p rocesses a re not n ecessarily d isturbance p rocesses. F or e xample, c ertain s edimentary p rocesses ( e.g., aeolian deposition) may not c ause a d isturbance t o c ultural r emains. Y et, a k nowledge o f t hese p rocesses i s c ritical f or i nterpreting h istory o f s ite f ormation. S ince the papers deal with a r ange o f n atural p rocesses, t he t itle change now accomodates a ll c onditions o f p reservation a nd modification. There were a number o f r easons why we f elt a volume d evoted t o n atural p rocesses was appropriate a t t his t ime. D espite t raditional c oncern f or p roving t he i ntegrity o f s ites, t here have been f ew s tudies which systematically d eal with the e ffects o f natural f ormation p rocesses. I nstead, the subject has been neglected o r only r eceived c ursory t reatment. Recent advances i n experiments, t aphonomy, ethnoachaeology, and geoarchaeology have g radually i ncreased our knowledge of the processes r esponsible f or c reating the a rchaeological r ecord. I n many i nstances, t hese e ndeavors h ave l ed t o t he s earch f or d evelopment o f n ew methods a nd t he c ritical a ppraisal o f a rchaeological i nterpretation. T he p ublication o f t hese papers r epresents the f irst compilation of t he r esearch e fforts o f numerous a uthors, working i n s everal p arts o f t he world. The papers cover a wide variety o f natural p rocesses r ather than one specific topic ( e.g., f luvial d isturbance). Though most o f the papers t reat specific s ite types and s ubjects, many o f t he approaches and observations transcend their particularistics. At minimum, t he r eader s hould r eceive a g reater a ppreciation

f or the i ntricacies i nvolved with formation o f the a rchaeological r ecord a nd p otential f or l earning which may make our behavioral i nferences more s ecure. As a c onsequence o f t he i ncreased c ommitment t o n atural p rocesses, t he i nformation p resented i n t he f ollowing p apers i s i nteresting a s a s ource o f t he a ccumulation o f n ew d ata and t he development o f n ew t heoretical a nd methodological approaches. I t was with t hese r easons i n m ind t hat we wished t o make t hese p apers a vailable t o t he a rchaeological c ommunity . There may b e s ome c onfusion p resent i n t he c urrent l iterature c aused by t he i nterchangeable u se o f s uch t erms a s " natural p rocesses", " noncultural p rocesses", and " environmental p rocesses". S ince t hese t erms a re p resently u sed i n a i nterchangeable f ashion, t here i s a n eed to develop a s tandardized terminology and conceptual f ramework ( see Hassan, N ash a nd P etraglia, t his volume). T his s hortcoming i s not r ectified h ere and r emains an i ssue which n eeds t o b e a ddressed . We must note t hat t he t opic o f c ultural f ormation p rocesses i s virtually absent i n this volume. We r ecognize t he e xtreme s ignificance o f h uman b ehavior a nd d o n ot wish t o imply t heir s ubversity by t he s tudy o f n atural f ormation p rocesses. B oth c ultural and n atural p rocesses i nteract i n c omplex ways a nd a re o ften d ifficult t o s eparate f rom e ach o ther. But, i n o rder t o d raw a ttention t o t he o ften i gnored n atural p rocesses, c ultural p rocesses a re n ot t he p rimary f ocus o f t his v olume. We must t hank o ur p rofessors a t t he U niversity o f N ew M exico, e specially L awrence S traus f or h is k een i nterest i n our e xperimental p roject and h is c ommitment t o o ur s tudies. A driana C ostanza G aray c heerfully p roofread t he p apers a nd h elped w ith t he p roduction o f t his v olume . We would l ike t o a cknowledge o ur e xtreme g ratitude t o a ll o f t he c ontributors, e ach o f whom d evoted t heir t ime and e fforts d espite s hort d eadlines. T hey have b rought t o t his volume a c ommon d esire t o l earn more f rom n atural f ormation p rocesses and a d iverse s et o f motivations, a pproaches, a nd v iews with which t o meet t hese g oals . We a re i ndebted t o B .A.R., Anthony H ands, and David Walker f or t heir i nterest i n publishing t his volume, and t heir p atience while we l abored t o t ie e verything together. F inally, b ut most i mportantly, we r eserve a s pecial t hanks t o o ur p arents who h ave s upported o ur e ndeavors.

M ichael D . P etraglia A lbuquerque, N ew M exico U .S.A.

D avid T . N ash F ort C ollins, C olorado U .S.A.

v i

A

R E-FORMING ARCHAEOLOGY: FOREWORD TO NATURAL FORMATION PROCESSES AND T HE ARCHAEOLOGICAL R ECORD F ekri A . H assan Washington S tate U niversity

T he a ct o f i magination i s t he opening o f s o t hat i t s hows n ew c onnections. J acob B ronowski

t he

s ystem

I n J une 1 877, a n a ging C harles D arwin ( 68 y ears o ld) and his wife Emma t ravelled to S tonehenge t o s tudy the e ffect o f earthworms on t he s inking o f t he f allen s tones ( Darwin 1 881). The r ole o f earthworms and o ther natural a gencies i n t he f ormation o f t he a rchaeological r ecord h as r ecently b ecome a matter o f r enewed i nterest. T he r easons f or the p resent i nterest i n natural p rocesses i s not a r esult o f a r ekindled i nterest i n e arthworms, b ut r ather a n e xpression o f a major t ransformation o f a rchaeological t hinking. A rchaeologists h ave b ecome k eenly aware t hat an u nderstanding o f t he h uman p ast c annot b e u ndertaken with a n e xclusive emphasis o n a rtifacts i n s hoeboxes d etached f rom both t heir physical c ontext and b ehavioral matrix. Debates on the s ignificance of variability between a rtifact a ssemblages a t a s ite a nd f rom d ifferent s ites, a s i n t he B inford 's-Bordes e xchanges, h ighlighted t he n eed to l earn more about how a rtifacts end up where they a re. Traditionally, a rtifact assemblages were assumed e ither e xplicitly o r t acitly to r epresent the r ange and f requency o f t ools p ossessed by various c ultural o r e thnic g roups. Accordingly i t was sufficient to c ompare and c ontrast a ssemblages t o g enerate s tatements a bout c ultural a ffinities, population movements, and d iffusion. The a ssemblages were mostly a rtifact c ollections f rom s ites o r " natural" l ayers. L ittle o r no attention was devoted to the sociocultural or natural processes that have c ontributed t o t he making o f t he c ollections. In the 1960s and the middle 1970s emphasis on s ociocultural p rocesses t riggered an i nterest i n the b ehavioral activities i nvolved i n the accumulation of artifacts and other archaeological remains at a rchaeological s ites ( e.g., Ascher 1 968; Cowgill 1 970; Ammerman and F eldman 1 974; Collins 1 975; H assan 1 976). S chiffer's Beh2vi2ral AIgl ae .215 2UY ( 1976) p resented a c oherent a nd a p ersuasive a rgument f or t he n eed t o e xamine b oth t he manufactural, u se, d iscard, a nd p ost-depositional p rocesses t hat i nfluence t he c haracter o f a rchaeological asse mblages. Such processes influence the spatial pattern, quantity, r elations, and f orm o f the potential a rchaeological o bjects ( Schiffer 1 976: 1 1). I n 1 983, S chiffer expanded h is views placing an emphasis on the p roperties o f a rtifacts a nd s ediments i n t he f ormation o f

1

t he

a rchaeological

r ecord.

My own r esearch on the composition of l ithic a rtifact a ssemblages f rom l ate P alaeolithic s ites i n U pper E gypt ( Hassan 1 974, 1 978a) c onvinced me o f t he s erious p roblems i nvolved i n t he i nterpretation o f a rchaeological data without an examination of the l ife history o r t rajectory o f a rtifacts f rom t he p rocurement o f r aw material t o t he moment o f r ecovery . My c oncerns were e xpressed l ater i n t he c ontext o f a g eneral analytical model f or t he s tudy o f l ithic a rtifacts ( Hassan 1 976 ). I c oncluded t hat a n a rchaeological c ollection " is. —not t o b e v iewed a s a mirror image o f t he r ange a nd c omposition o f a rtifacts i n a ctual, o rdinary c ultural l ife" ( ibid.). The potential for cultural i nterpretation of a rchaeological c ollections, a s I n oted t hen, i s i nfluenced by a lterations or l oss of the o riginal position, composition, association, and mutual r elations of a rtifacts. My own work s ince that t ime i nvolving a rchaeological a nd g eological s tudies o f s ites f rom different t ime periods and of d ifferent k inds of collections has confirmed my belief i n the u tmost importance t hat s hould be a ssigned t o s ite f ormation p rocesses i n a rchaeology. A rchaeological s urveys a nd e xcavations r arely, i f ever, r eveal a f rozen s lice f rom t he c ultural p ast. T o begin with, o nly a f ew k inds o f h uman b ehavior l eave a material t race. E ven a s materials a re deposited f rom a c ultural e vent, dogs, children, bacteria, wind, r ain or gravity begin to alter the physiognomy o f t he potential r ecord. E ven when t he archaeological materials a re buried r apidly after d eposition, t he a rchaeological r emains a re not immune a gainst t ranslocation, a brasion, d ecay, o r t otal r emoval. The c omposition a nd i ntegrity o f a rtifacts i n a s ealed c ontext a re n ot n ecessarily p ristine. A rchaeological r emains a lso may r e-surface t o b e f urther r e-worked b efore t hey a re b uried a gain . As a proxy to the human c ultural past, the a rchaeological r ecord i s p artial, p atchy, c omposite, muddled, a nd c ertainly muffled. T his i s a bundantly c lear f rom t he c ontributions i n t his v olume, r egardless o f t he e nvironmental c ontext o f t he a rchaeological r emains, e .g " James S avelle o n i gloos f rom A rctic C anada; V irginia B utler o n s almonid d eposits i n t he P acific Northwest; Michael P etraglia, David N ash, K athy S chick, a nd K . P addayya o n r iverine p rocesses; L uAnn Wandsnider o n d une s ites; J on E rlandson a nd T homas R ockwell o n c oastal s ites; a nd M . S chiffer e t a l. o n mud-walls i n n orthern C hile . T he u biquity o f n atural a nd c ultural p rocesses t hat d istance t he a rchaeological p resent f rom p ast c ultural e vents o f k ey i nterest f orces upon u s t he n eed f or a c oherent p aradigm t o g uide a rchaeological i nvestigations ( Gifford 1 977: 3 08, 1 981). I n t his v olume, t here i s a

2

c ontrast b etween t he s o-called e pisodic p aradigm a nd t he p rocessual p aradigm ( cf. Wandsnider, N ash a nd P etraglia ), r ekindling a p reviously d ebated i ssue ( Binford 1 981; Schiffer 1983). In the episodic paradig m, the a rchaeological r ecord i s c onceived a s d ifferentially c onserving episodes o f both h uman a nd n atural behavior t hrough t ime. T he a rchaeological r ecord r esults f rom t he a ccretion a nd d ifferential s urvival o f r emains r eflecting " ethnographic i nstants". I n t he p rocessual p aradigm, t he a rchaeological r ecord i s s een a s f orming t hrough t he i nteraction of natural and cultural behavior. The p reservation o f s ingle e vents, n atural o r h uman w ithin t he c ontext o f t his p aradigm, i s r egarded a s e xceedingly r are. I am n ot p articularly h appy w ith t he d ichotomy, a lthough I am k eenly aware o f, a nd s upport, t he i mportance o f many o f t he points r aised. H owever, t he s tudy o f t he p rocesses i nvolved i n t he m aking o f t he a rchaeological r ecord d oes not r epresent an alternative strategy that must by n ecessity n egate c onsidering t he p ast i n t erms o f e vents a nd s equences o f e vents. I n f act, i t i s i nconceivable t o t hink o f p rocesses without e vents. I t s eems t o me t hat t he main p oint i n t he p olemic i s n ot t he d ichotomy b etween " episodes" a nd " processes", b ut t hat t he a rchaeological r ecord d oes n ot c onsist o f c ultural r emains t hat a re l ater d isturbed. Rather, the processes r esponsible for g enerating, o rganizing, p reserving, and p resenting t he a rchaeological r ecord s hould b e v iewed s imply a s f ormation p rocesses. T his p erspective i s u seful b ecause a ttention i s d rawn t o t he dynamic l ife h istory o f a rchaeological r emains a nd t he r ole o f p rocesses o f d ifferent t emporal f requency o n t he u ltimate p osition, c ontent, a nd p attern o f a rchaeological r emains. This p erspective p rovides a s trong a ntidote t o t he f acile , " reconstitution" o f c ulture b y " correcting" f or a pparent d isturbances o r d istortions. What needs to be emphasized here are the i mplications f or r esearch g oals a nd o bjectives o n t he way we v iew t he a rchaeological r ecord. Archaeologists, f or e xample, h ave f or s ome t ime b een i nterested i n t he m eaning o f i nterassemblage v ariability. D ifferences between a ssemblages have often been phrased i n terms of e thnocultural a ffiliation, t emporal t rends, r egional v ariants, t echnomanufactural d ifferences, a nd f unctional d ifferentiation. An a rchaeologist who a ssumes t hat a c ollection o f a rtifacts f rom a n a rchaeological o ccurrence r epresents t he u nmistakable f ingerprint o f a n e thnic g roup which c an b e r eadily matched with a nother t o a scertain f iliation o r d raw e thnic b oundaries i s, i n my o pinion, b oth u naware o f t he a rticulation b etween material r emains a nd s ocial systems, and of the mäny s ources of variability i n a rchaeological a ssemblages. I nterpreting t he c ontent a nd f requency o f a n a rchaeological a ssemblage must b e g rounded i n a n u nderstanding o f both t he behavioral a nd natural

3

events that have i nfluenced the presence/absence, a lteration, a nd d isplacement ( relative t o i t a s a p rimary s ite o f manufacture, u se o r d iscard) o f i ts i ndividual c omponents a nd o f t he a ssemblage a s a whole. S ome o f t he e vents may n ot be r elevant t o a s pecific q uestion. An a nalysis o f t he s ignificance o f t he e dge angle o f a n a rtifact f or e valuating i ts p otential a s a k nife w ill n ot b e a ffected by t he d isplacement o f t he a rtifact. By c ontrast, a n a ttempt t o c onjoin p ieces t o e stablish t he p rimary l ocus o f a f lint-knapping e vent(s) must t ake i nto c onsideration t he d ispersal o f o bjects d uring manufacture a nd t he d eliberate o r i nadvertent d isplacement o f f lintk napping p roducts d uring, s hortly a fter, a nd l ong a fter t he a ctivity h as t aken p lace. T his may i nvolve both s urficial a nd s ubsurface p rocesses . I n t his i nstance, a ny d isplacement o f t he p roducts o f f lint-knapping, f or e xample, t hrough t rampling, sweeping, o r d eflation may i nterfere with o ur a bility t o r econstruct t he f lintk napping t echnique o r t he s patial a spects o f t he s tonemanufactural a ctivity . A knowledge of the noncultural processes can minimize t he " noise" t hat i nterferes with t he c ultural message. H owever, post-depositional p rocesses c an b e a v aluable s ource o f c ultural i nformation. F or e xample, c eramics d iscarded o r d ropped a long a path a re l ikely t o be t ransformed i nto small, abraded, and r andomly d istributed s herds. Attention t o a ttributes, s patial patterning, and contextual r elations f rom primary c ultural, taphonomic, penecontemporaneous a nd p ostd epositional p rocesses c an t hus b e u sed t o e valuate t he v alidity o f c ertain c ultural i nferences, a nd d irectly a s a s ource o f c ultural i nformation. R ecognition o f a p ath-way f rom d isturbed c eramics, s torage a reas f rom c oncentration o f r odent h oles a nd t heir a ctivities, l iving f loors f rom a l ow c oncentration a nd a l ow d iversity o f a rtifacts b ecause of f requent sweeping, and agricultural f ields f rom e rosional s cars a re s ome e xamples o f h ow p rimary c ultural a ctivities c an b e i nterpreted f rom b ehavioral a nd n atural p rocesses t hat a lter o r modify t he l ocation, f orm, a nd r elational a ttributes o f p rimary f eatures. We a lso n eed t o r eexamine t he n ature o f t he b asic a nalytical u nits u sed i n a rchaeological i nvestigations. F or e xample, a n a rchaeological a ssemblage i s f irst a nd f oremost a d ivision i mposed o n t he a rchaeological r ecord by t he a rchaeologist. O ne o f t he f irst q uestions i s, what a re t he c riteria employed by a rchaeologists t o d efine a n a ssemblage? I s a n a ssemblage a c ollection f rom t he s ame l ithostratigraphic u nit, a c ollection f rom a s pecific square a nd l evel i n a n e xcavation, a c ollection f rom a s catter o f a rtifacts, a c ollection f rom a rtifacts t hat a re i n c lose s patial p roximity, o r a c ollection c orresponding t o t he r emains f rom a s ingle, d iscrete s ettlement o r a n o ccupation? B inford ( 1982: 5 ), f or e xample, c haracterized

4

a ssemblages a s " sets of a rtifacts ( both i tems and f eatures) which a re f ound a t o r i n a rchaeological s ites." H e ( 1982: 5 -6) a lso r ightly n oted t hat t he d egree t o which a ssemblages, s o d efined, " may b e t reated a s t he r esults o f occupations, or the material derivatives fro m u ninterrupted u se o f a s ingle p lace by participants i n a c ultural s ystem, i s y et t o b e c larified". I n t he p ast, t he t erm a ssemblage h as b een u sed t o r efer t o a c ollection o f a rtifacts f rom a n a rchaeological l ayer (5 / 1 . 1che ) o r a s patial c luster o f a rtifacts a t s urface s ites. I t was a lso c ommon t o a ssume t hat s uch a n operational e ntity c orresponds i n c omposition a nd f requency t o t he t otal i nventory o f a rtifacts c haracteristic o f a s ociocultural ( ethnic) g roup. This has b een r esponsible f or many s tatements a bout c ulture, p hylogenetic c ultural a ffinities a nd d iffusion/population movements that a re s eriously f lawed, or at best unjustified ( Binford 1982). U ndoubtedly a n u nderstanding o f p rehistory c annot be a chieved w ithout a c larification o f t he various f actors a nd processes that contribute to the making of an a rchaeological c ollection. My p reference a t t his m oment i s t o d iscontinue u sing t he t erm " assemblage" when r eferring t o a n a rchaeological c ollection. T he f irst t ask a head o f u s, o nce we h ave made t he conceptual s eparation between a collection of a rchaeological o bjects a nd t he c ultural p ast, must c onsist o f a c larification o f t he r ole o f the b ehavioral a nd n atural agents and processes that i nfluenced the t rajectory of each archaeological object and the c ontextual r emains f rom a l iving p ast t o a n a rchaeological p resent. These a gents a nd p rocesses c oncern t he s ource, u se, d isuse, l ocational movement, p hysical d urability, a nd c hemical s tability o f t he a rchaeological o bjects. T here i s u ndoubtedly a n eed f or e thnoarchaeological i nvestigations to i nform general models of r ange, l ocation, a nd f requency o f materials g enerated i n v arious b ehavioral s ituations. B inford's ( 1980) r ecognition o f t he r elationship b etween i nter-assemblage v ariability a nd t he duration o f o ccupation, a s a f unction o f s patial m obility, u nderscores t he i mportance o f a n u nderstanding o f t he o rganizational/behavioral a gents a nd p rocesses i nvolved i n g enerating potential a rchaeological r emains. F actors i nfluencing t he a ccumulation, modification, a nd l ocation of a rchaeological r emains are numerous. E thnographic, s edimentological, t aphomomic, a ctualistic, a nd e xperimental work will c ontinue t o p rovide u s with i nsights, but we must also not overlook the g eoarchaeological s tudy o f a rchaeological o bjects a nd s ediments t o d ecipher t he d evelopmental h istory o f a s ite ( Hassan 1 978b: 2 09ff). The g eomorphology o f a s ite, i ts m icrostratigraphy, c hronology a nd l ithology, a re e ssential f or evaluating the duration of human occupations, i ntermittency o f o ccupation, r ate o f s ite f ormation,

5

l ocation o f a ctivity a reas, a lterations.

e rosion,

a nd p ost-depositional

The co m m on te nde n c y to ass u me tha t l ithostratigraphic l ayers ( so c alled n atural s tratigraphy ) p rovide c ollections c orresponding t o c ultural e ntities p resupposes t hat s edimentary e vents c ovary w ith c ultural e vents, a position r ightly denounced by B inford ( 1982: 1 7). I s uppose t hat a rchaeologists t acitly a ssume t hat t he c ovariance b etween s ediments a nd a rtifacts r esults f rom t he s imultaneous a nd equally e ffective impact of c limatic/environmental c hange o n c ultural a nd physical p rocesses. T his i s p atently wrong. M oreover, d ifferent l ayers i n t he s ame s equence o r i n d ifferent s patial l oci a t a s ite may h ave r esulted f rom a s ingle o ccupation. F or t his r eason, microstratigraphy, d endrochronology, a nd p recise r adiocarbon a ge d eterminations a re n ecessary t o e stablish the c ontemporaneity and t he t ime-value of a rchaeological u nits. T his i s a n i mportant v ariable s ince d iversity i n a n a ssemblage i s a f unction o f t he r ecurrence o f t he s ame o r d ifferent a ctivities. Two a rchaeological c ollections r elated t o a s ingle c ultural g roup may d isplay d ifferent c omposition o r f requencies. G eoarchaeological i nvestigations a t a s ite s hould a lso f ocus o n t he r ecovery o f i nformation t hat would s uggest i f certain r emains are l ikely to have been d estroyed, d ifferentially p reserved, o r r e-assembled. A rchaeological d eposits i n c olluvium a re l ikely t o h ave b een r eworked by s urface r unoff, c arbonate s hells i n a s ite with a n a cidic pH a re l ikely t o d issolve, a nd an a rchaeological c ollection a t a s urface may r epresent a l ag o r r esidual a ccumulation r esulting f rom t he e rosion o f t he s edimentary matrix i n which t hey were o nce e nclosed. T he e ffect o f e rosion o f t ells, mounds o f v illage o ccupations i n t he N ear E ast, o n t he d ensity a nd c omposition of c eramic s herds i n t he v icinity o f t he t ells i s p ronounced ( Kirkby a nd K irkby 1 976; R osen 1 986). Any a ttempt t o u se c eramics f or s eriation, p opulation e stimates, o r l ocating activity areas without considering erosion is q uestionable. I n d ealing w ith " assemblages" n atural p rocesses a re r elevant i f o ne d esires t o a sk the k ind o f q uestions a rchaeologists a re i nterested i n, i ncluding t hose r aised b y B inford a bout s patial mobility a nd t he c omposition a nd diversity of artifacts. In the c ontext of the U .S. S outhwest a rchaeology, t he c oncept o f a ssemblage i s r elated t o c ollections f rom h ouse f loors ( Schiffer 1 985). S chiffer r ecognizes a v ariety o f f ormative p rocesses t hat may c ontribute t o t he making o f a h ouse f loor a ssemblage a nd c arefully maintains t hat a n a rchaeological a ssemblage cannot be considered as a r eliable proxy to r oom a ctivities without a c onsideration o f t he f actors t hat i nfluence t he c omposition o f t he i nventory l eft b ehind

6

when t he a rea o ccupied i s v acated. S chiffer r ecognizes v arious k inds o f r efuse a ssociated with the p eriod o f o ccupation and the period prior to and following a bandonment. H e a lso n otes t he possible impact o f the mode o f a bandonment; c atastrophic, f inal, o r t emporary. A nalytically, S chiffer r egards what h e c alls " de f acto" r efuse, meaning a rtifacts, o ften s till u sable, t hat a re l eft behind when people abandon activity a reas, s tructures, a nd s ettlements, a s t he a ppropriate u nit f or f unctional a nalysis. H e notes that i n s everal c ases, i tems f rom d e f acto r efuse a re l ess n umerous t han m ight b e e xpected f or v arious r easons; e .g., r emoved t o a n ew o ccupation o r l ooted. S chiffer a lso p rovides c riteria f or a ssessing the f actors t hat l ead t o a depletion o f t he de f acto r efuse. S chiffer 's a pproach a nd methodology f or i nterpreting t he c ollections f rom h ouse f loors a re appropriate a nd f undamental. A c ollection o bserved o r a nalyzed by a n a rchaeologist f rom a h ouse f loor i s ar esult o f a s equence o f e vents a nd d ecisions . I f o ne w ishes t o make i nferences a bout r oom f unction(s), t he f actors that a re l ikely t o o bfuscate, b lur, o r b ias t he material evidence must be i dentified a nd t heir impact a ssessed. There i s a lso a n eed f or e valuating t he s ocial, behavioral, and n atural f actors t hat i nfluence t he o riginal c omposition and d istribution o f m aterial r emains d uring o ccupation. T his i s t he importance o f the c ontributions made by B inford a bout s patial mobility, duration o f o ccupation, and a ssemblage c omposition. A r oom o ccupied f or a f ew y ears i s l ikely t o y ield material r emains d ifferent f rom t hose i f t he o ccupation l asted f or f ifty y ears o r more. P eople may a lso change t he f unctions o f r ooms a s a r esult o f c hanges i n f amily c omposition o r s ocial a ttitudes. A r econstruction o f a s ite d evelopmental h istory a nd a n i dentification o f t he natural a nd behavioral events r esponsible f or a n a rchaeological c ollection a re o bviously n ot a n e asy t ask. They c annot be based s oley o n ä d l a s IQ m ethodology, o r u nderplayed b ecause t hey a re n ot a p art o f t he a rchaeologist's world v iew, o r because t here a re no s hort-cuts o r a c ook-book r ecipe available y et. I may a lso a dd that a n a ssessment o f s ite f ormation p rocesses c annot b e done by a narrow f ocus on t he materials f rom a r oom o r ac ollection f rom a l ayer without t he benefit of a c omprehensive s tudy on the whole s ite, o ther s ites, and o ff-site r emains i n the r egion, as well a s the g eoarchaeology o f the r egion. Rosen's ( 1986) work o n t ells c learly d emonstrates t he i mportance o f t he s tudy o f d erived a rchaeological r emains i n the a rea o f a s ite i n e valuating t he r ole o f n atural a nd h uman a gencies i n s ite f ormation. I n t he p resent v olume, s everal a ttempts a re a imed a t e xpanding o r s harpening o ur k nowledge o f t he n atural

7

p rocesses o n t he b asis o f e thnoarchaeological o bservations ( Savelle, Schiffer et al.) f ield studies of natural occ urr ences (Butler, Wandsnider) , and field e xperimentation ( Petraglia and Nash). Other s ources of i nfor mation include laboratory experiments under c ontrolled c onditions ( e.g " aqueous t ransport o f b one by B ehrensmeyer 1 975), historical s tudies that can shed i nfor mation on natural disturbances over long ti me p eriods, a nd g eoarchaeological i nferences b ased o n welld ated e vents i n c ontrolled s ituations, a s well a s c omputer s imulations. R EFERENCES Ammerman, A .J. a nd M .W . F eldman 1 974 On the Making of an Assemblage American Antiquity 3 9: 6 10-616.

o f

S tone

Tools.

Ascher, R . 1 968 T ime's A rrow a nd t he A rchaeology o f a C ontemporary Community. In ß . ettlement l i Ig .häe s /12uy, edited by K .C. Chang, pp. 4 3-52. National Press Books, Palo A lto. B ehrensmeyer, A .K. 1 975 The Taphonomy and Palaeoecology of PlioPleistocene Vertebrate Assemblages East of Lake Rudolf, Kenya. Bullgtin g l f t he m maeum gf gmp .ärätivg Z oology, H arvard U niversity 1 46: 4 73-578. B inford, L .R. 1 980 Willow Smoke and Dog's Tails: S ettlement Systems and Archaeological American Antiquity 4 5: 2 55-273. 1 981 B ehavioral A rchaeology a nd t he J ournal 2f Anthropological R esearch 3 7: 198 2 The Ar c haeol og y A nthropological A rchaeology 1 :

Hunter-Gatherer S ite Formation.

" Pompeii 1 95-208.

of Place. 5 -31.

P remise".

JQu Ln äl

of

Collins, M .B. 1 975 S ources o f B ias i n P rocessual D ata: An Appraisal. I n S ampling i n A . r . häe2ig luy , edited by J .W. Mueller, pp. 2 6-32. U niversity o f A rizona P ress, T ucson. Cowgill, G.L. 1 970 So me Sampling and Reliability Problems in Archaeology. In AIQ .hA212aie et älgA lläteur .al _ Ers 2hl mee Zemil2aiumea et MäthAmätiaL iee, pp. 16 11 75. Colloques Internationaux du CNRS. Editions du CNRS, P aris. D arwin, C . 1 881 The

F 2rmäti2n

2 f

M euetätie 8

m 2i tld

T hr2u21

t he

Action o f Worms.

Murray,

L ondon.

G ifford, D .P. 1 977 O bservations o f C ontemporary H uman S ettlements a s an Aid to Archaeological Interpretation. Ph.D. dissertation, University of California, Berkeley. U niversity o f M ichigan Microfilm, Ann A rbor. 1 981

T aphonomy a nd

Archaeology's 4 38.

A cademic

P alaeoecology :

S ister

Disciplines.

Meth s /d änd T h

P ress,

N ew

A C ritical

Y ork.

y,

R eview

o f

I n ä dvän ez i n v ol. 4 , p p. 365-

Hassan, F .A. 1 974 T he A rchaeology o f D ishna P lain: A S tudy o f a L ate Palaeolithic S ettle ment. The . . e _212g .i2ä1 _ au _z _y _ y 2f E gypt ., Paper no. 5 9, Cairo, Egypt. 1 976 T he S tudy o f L ithic A rtifacts: An Analytical Model and Two Case Studi es. In PLimiLime ALL änd Te .2hn212gy, edited by J .S. Raymond, B . Loveseth, G . Arnold, and G . Reardon, pp. 27-46. University o f C algary, C algary . 1978a The S ebilian of the Nile Valley: Some New Concepts. In View a 2f P äat, edited by L .G. F reeman, pp . 1 53-176. Mouton, The H ague. 1 978b S ediments i n A rchaeology : Methods a nd Implications for Palaeoenviron mental and Cultural Anal ysis. J ournal 2f F ield A rchaeology 5 : 1 98-213. K irkby, A . and M .J. Kirkby 1 976 G eomorphic P rocesses and the S urface S urvey of Archaeological Sites in Se mi-Arid Areas. In _ G egärch m .212 .gy, edited by D .A. Davidson and M .L. S hackley, pp . 2 29-253. Duckworth, L ondon. Rosen, A .M. 1986 n tie _a 2 f C hicago.

Zläy.

University

S chiffer, M .B . 1 976 B ehavioral A rchaeology .

of

A cademic

1 983 T oward t he I dentification American Antiquity 4 8: 6 75-706.

o f

Chicago

P ress,

F ormation

Press,

N ew York. P rocesses.

1 985 I s there a " Pompeii P remise" i n Archaeology? J ournal 2 .t Anthropological R esearch 4 : 1 8-41.

9

D ETERIORATION O F ADOBE S TRUCTURES: A CASE S TUDY FROM S AN P EDRO DE ATACAMA, N ORTHERN C HILE M ichael B . S chiffer, U niversity o f A rizona Ana

Marla B aron, P aulina P auchard Cortds, a nd J avier T amblay S epulveda S antiago, C hile

I NTRODUCTION I n the Atacama Desert of northern Chile l ies and upland oasis, San Pedro de Atacama, i nhabited for millennia. One of us ( AMB) has been carrying out a rchaeological i nvestigations i n t hat z one f or a n umber o f years, most r ecently i nvolving excavations at the e arly a gricultural s ite o f Tulor Aldea ( Bardn and Vallejo n .d.; l lagostera e t a l. n .d.). F or s everal d ays i n S eptember o f 1 985, a s part o f the Tulor Aldea P roject, we undertook ethnoarchaeological f ieldwork at n earby Tulor Ayllu, a small s ettlement o n t he verge o f t otal a bandonment. O ur a im was t o d ocument t he d eterioration p rocesses o f a dobe s tructures i n t his e xtremely a rid e nvironment i n o rder t o provide i nsights that could be applied to t he r emains of s imiliar a rchaeological s tructures a t T ulor A ldea. T his p aper p resents o ur b asic f inding, which h ighlight t he mix o f c atastrophic and noncatastrophic p rocesses that have c ontributed t o s tructural d ecay a t T ulor Ayllu. ENVIRONMENT O F

S AN P EDRO D E ATACAMA

T ulor Ayllu i s l ocated i n t he n orth o f C hile, i n t he i nterior of R egion I I, Antofagasta. Topographically, t here a re t hree b asic l andforms--as i n t he r est o f C hile-arranged in longitudinal bands: the coastal r ange ( c su _diiieLä d e l a . C2sta), intermediate depression ( 2epLeaiOn i nte/medi ), and the Andean Range ( CordilleLä de Loa Andes). In the a rea of most i nterest to u s the local mountain r anges, for med of folded Mesozoic sedi ments, are kno wn as the precordillera. The p recordillera appears c learly i ndependent o f the main mountain c hains i n t hree a reas: i n t he L oa V alley, t o t he north o f Calama, and by the g reat t ectonic depressions toward the south. The precordillera runs in a s outheasterly d irection, and i n the S an P edro de Atacama i t i s c alled t he D omeyko R ange. E nclosed within t he Andean R ange a nd b etween i t a nd t he P recordillera e xist t ectonic d epressions that a re considered as i ndependent s tructural e ntities; the best k nown o f t hese a re the basins of C alama and Salar de Atacama. The l atter, which t akes i n an area of 3 ,500 km, h as s urface a nd u nderground water s ources, i ncluding r uno ff f rom t he s urrounding h ills. I n t he n orth o f t he S alat

1 0

d e Atacama f low t he S an P edro and V ilama R ivers, whose w aters d erive f rom t he A ndes, p ermitting t he d evelopment o f b iotic c ommunities i n t he m idst o f t otal d esert. T he Andes r each a n a ltitude o f 6 ,000 m i n t his r egion, d escending t oward t he w est i n a n i nclined p lane o f a lluvial f ans, e ventually f illing t he basin o f S alat d e A tacama, which i s a t a n a ltitude o f 2 ,300 m . T he D omeyko R ange o n t he west r eaches a maximum a ltitude o f 4 ,600 m a t Q uimal P eak. O n t he s outh, t he S alat d e Atacama i s b ounded b y v olcanic o utcrops d eriving f rom t he e ast. T he a vailability o f s urface water i n t his e nclosed b asin h as p rovided a microenvironment s uitable f or s upporting l ife. T his upland o asis, which t oday c ontains a bout 2 ,000 i nhabitants, i s k nown a s S an P edro d e A tacama. O ne o f t he most i mportant g eomorphological p henomena a t t he l ocal l evel i n t he S an P edro d e Atacama i s t he s and d unes, which a re a dvancing f rom t he n orthwest ( Valle d e L a L una o r C ordillera d e l a S al) t oward t he s outheast. L ittle b y l ittle, t he wind-borne s ands a re c oming t o c over important f ertile s ectors of San P edro de Atacama. I ndeed, a n e normous dune, which passed over t he s ite o f T ulor A ldea, i s n ow e ncroaching u pon t he w estern margin o f T ulor Ayllu ( figure 1 ). Although S an P edro d e Atacama i s l ocated i n t he s ame l atitude a s Säo P aulo, B rasil--a r egion o f h igh p recipitation a nd t ropical vegetation--the l andscape on t he western s ide of the Andean massif i s utterly d ifferent. A c onjunction o f s everal f actors c ontributes t o t he a ridity o f t he Atacama D esert, i ncluding P acific a nticyclones t hat g enerate s ubsiding h ot a nd d ry winds a nd the i nfluence o f the cold Humboldt current. These m eteorological e ffects h ave p roduced a n i mpressively d ry a nd b arren d esert i n s outhern P eru a nd n orthern C hile. F rom the s tandpoint o f t emperature, t here i s g reat d iurnal v ariation, which r esults i n p art f rom t he e xtreme d ryness o f the a ir. The d esert c limate g ives f ree r eign t o s olar r adiation a nd i nsolation, p rovoking h igh d aily a nd l ow n ightly t emperatures. I n S an P edro de Atacama, s ummer t emperatures f luctuate b etween 3 5° C i n t he d ay a nd 1 0° C a t n ight; i n winter, t hey vary b etween 1 7° C i n the d ay a nd 8° C i n t he c oldest n ights. P recipitation i s e xtremely s carce d uring t he major p art o f t he y ear; i n s ome y ears t here i s a bsolutely none. P recipitation r ecords f or t he S an P edro d e A tacama p roper a re l acking, b ut d ata f rom C alama a nd o ther n earby c ities c onsistently i ndicate a mean annual p recipitation o f 1 mm--or l ess. I t i s possible t hat S an P edro d e Atacama, being closer t o the Andes, r eceives s lightly more p recipitation. S ummer i s t he most h umid s eason, when t he d irection o f t he wind c hanges a nd warm t ropical f ronts

1 1

approach, s ometines p rovoking violent r ains and g reatly a ugmenting r iver f lows. T hese e lectrical s torms o riginate i n the eastern s ide of the Andes; a t t imes they r each the Domeyko Range and, more r arely, t he Calama basin, 1 00 km t o t he w est o f S an P edro. The natural vegetation of t he oasis i s c omposed p rincipally o f A lgarrobo ( Prosopis c hilensis) a nd C hahar ( G2uLliaea de rlicans). Both s pecies a re l eguminous t rees t hat c ommonly r each a h eight o f 3 -4 m ; t hey p rovide construction material, f uel, and t he s eeds and pods a re important a s c amelid f odder and, f ormerly, a s f ood f or humans. Various shrubs g row a long the r ivers and s alt pans, s uch a s La B rea, which i s u sed i n constructing r oofs. T he s hrubs a lso i nclude C achiyuyo ( Atriplex s pp .), w hich g rows i n s and a nd s lows t he a dvance o f t he d une. A s

f or

a nimals,

t his

r egion

i s

important

mainly f or

t he h erding o f c amelids, e specially l lamas ( Lama ai m ). T he r elationships b etween h umans a nd c amelids h ave a g reat a ntiquity; c amelid b ones a re a bundant i n T ulor A ldea, j ust after the ti me of Christ, and pens have also been r ecorded. A small r odent i s f ound today, mainly i n a gricultural f ields. T ULOR AYLLU Tulor Ayllu i s a dispersed, r ancheria-type s ettlement c ontaining s everal dozen a dobe s tructures i n v arious s tages o f d eterioration, a nimal p ens, t he r emnants of f ields, and a c anal system that i s l argely i n d isuse. Two houses a re s till employed on a year-round basis as dwellings; o ne by a n a ged b rother a nd s ister, t he o ther by an e lderly man. S torage of Chahar and s undry materials was o bserved i n a f ew s tructures. S till o ther s tructures and t ofts a re u sed as s easonal c amps f or c amelid h erding by r esidents of nearby ayllus. A f ew of t he abandoned s tructures r emain habitable, whereas o thers would be r egarded a s r uins o r house-sites by a rchaeologists. At t he t ime of our f ieldwork, i n 1 985, p lans had been made to c lean out and r eactivate the c anal system, which i s n ecessary f or g rowing c rops. The l ast h arvest t ook p lace i n 1 979. S urface r emains of Archaic and c eramic period o ccupations t estify t o human o ccupation o f the T ulor l ocality d uring t he p ast s everal m illennia. H owever, we h ave n ot o btained i nformation a bout t he e arly h istory o f the p resent-day s ettlement of T ulor Ayllu. The t erm " ayllu" i mplies a c ommunity-level o rganizational u nit o f the I nca Empire ( cf. Mason 1 968: 1 74), but s uch a small village l ikely d id not l eave a t race i n the h istoric r ecords of Spanish Colonial times. Thus, despite i ndications of c onsiderable antiquity f or Tulor Ayllu ( perhaps back to the I ncas), we have no d irect evidence

1 2

beyond i nformant r ecall. Although one house was r eportedly built a round 1 800, most o f t he i nformation s upplied by our i nformants pertains to the present c entury. I n a ll p robability, T ulor Ayllu r eached a maximum p opulation o f 2 0-30 households i n t he e arly t wentieth c entury . J udging by t he h ouse r uins, w e s uspect t hat t he c ommunity was n ever much l arger t han t his. S everal f actors s eem t o have c ontributed t o t he l engthy d ecline o f T ulor Ayllu during t his c entury, s ome o f which markedly a ffected t he d eterioration p rocesses o f s tructures. A ccording t o o ur i nformants, a typhoid e pidemic swept t he v illage i n 1 931, k illing many r esidents a nd l eaving T ulor Ayllu n early d epopulated . A lthough we h ave b een u nable t o o btain i ndependent d ocumentation f or t his epidemic, t yphoid was a s erious s courge i n Chile a t t hat t ime ( cf. D onoso a nd Moroder 1 943); t here i s l ittle r eason t o doubt o ur i nformants' r ecollections. Major e arthquakes s truck twice, p robably i n 1 931 a nd 1 952 a ccording t o o ur i nformants, causing damage t o o ccupied a nd a bandoned h ouses. H istoric r ecords s how t hat t he g reater north o f C hile ( between 1 9 a nd 2 8° l atitude) i s s eismically q uite a ctive. F or e xample, b etween 1 929 a nd 1 955 f our earthquakes e xceeding a magnitude o f 7 .0 t ook p lace, i ncluding o ne e ach i n 1 929 and 1 947 ( Barrientos P arra 1 980). I n a ddition, being a t t he e nd o f t he l ocal c anal s ystem, which d raws i ts water f rom t he S an P edro R iver, T ulor Ayllu e njoys n either g ood n or r eliable water. I ndeed r esidents a t the t ime o f our v isit had t o s ecure water a t s ome d istance o n f oot. The water s ituation was c ited most o ften by i nformants a s the c ause o f T ulor Ayllu 's d ecline. F inally, t he f actor t hat would p robably b e i dentified by a rchaeologists a s most s alient i s the immense s and dune t hat h as b egun t o move o ver the v illage. A lthough i nformants d id not mention t he d une a s a f actor c ontributing t o T ulor Ayllu's a bandonment p rocess, an awareness o f t his d une's movement might h ave a ffected h ousehold d ecisions a bout r esidence a nd h ouse r ebuilding. Moreover, the menacing dune perhaps d iscourages r ecolonization. A more s atisfactory a ccount o f t he c auses o f T ulor A yllu 's a bandonment would r equire a c onsideration o f t his s ettlement w ith r espect t o f actors o f r egional, n ational, a nd i nternational e conomic s ystems. D ecisions t o a bandon o r not t o r esettle, made o n a household basis, were p robably i nfluenced g reatly by t he i ntegration o f that h ousehold--and T ulor Ayllu--into t hese l arger e conomic s ystems. F or e xample, a c omprehensive model o f T ulor a bandonment p rocesses would p robably i nclude r eference t o t he worldwide e conomic d epression o f t he 1 930s a s well a s the collapse o f the nitrate mining i ndustry i n the Antofagasta-Calama a reas i n the l ate 1 920s a nd e arly 1 930s, both o f which a ffected employment opportunities a vailable t o r esidents o f t he smaller c ommunities.

1 3

I n a ny e vent, t hese f actors t ogether h ave l ed t o t he Tulor Ayllu of today, a s ettlement that i n a ll l iklihood will b e c ompletely a bandoned ( for y ear-round h abitation) within a decade or two. Although we can approach T ulor Ayllu as an archaeological s ite, s ince i t i s mostly i n a rchaeological c ontext a lready, t he a bility o f r esidents a nd f ormer r esidents ( and t heir r elatives) t o p rovide s ome i nformation on the l ife h istory o f s tructures g ives u s a certain measure of control u navailable i n most purely a rchaeological s ettings. O ur i nformation i s v ery u neven, however, and i n no case do we have e xact dates of house construction and abandonment ( table 1 ). Even s o, the i nformation we do possess makes i t p ossible t o appreciate the mix of processes--cultural a nd noncultural, s lowacting and catastrophic--that have c ontributed ( and are c ontributing) t o s tructure d eterioration a t T ulor Ayllu. C ONSTRUCTION T ECHNIQUES The s tructures of Tulor Ayllu ( and i n neighboring s ettlements) a re mostly b uilt o f t apialeras, l arge a dobe blocks for med in place with molds. Each block is approximately 1 m long, . 5 m wide, and . 75 m h igh ( see f igure 2 ). The molds are f illed with chunks of c lay and only enough water to make a f irm a dobe i s a dded; no r eal mixing t akes p lace. R ather, t he a dobe i s p ressed i nto t he mold with blows f rom a 1 1-12 k g weight. I n addition, as l ayer upon l ayer of clay i s added t o the mold ( note the l ayering i n f igure 2 , especially l ower r ight), a l arge s teel spike, about 2 m long and 3 -4 cm i n diameter, i s u sed t o chop up the chunks o f c lay. Chains o r bolts hold fast the parts of the mold. After each block is c ompleted, t he mold i s u nfastened a nd a n ew b lock i s b uilt n earby. T apialera c onstruction may h ave g reat a ntiquity i n this r egion. For example, i t appears that Tulor Aldea, which d ates t o t he e arly c enturies A .D., was made o f a dobe b locks f ormed i n p lace. More typical adobe construction based on small b ricks i s a lso f ound at Tulor Ayllu ( figure 3 ). S till other structures exhibit hybrid brickc onstruction ( figure 4 ); i n every c ase adobe bricks a re p resent i n the upper portion of walls. We suspect but c annot d emonstrate t hat hybrid c onstruction r esults f rom r epair o r r ebuilding episodes a fter e arthquakes. We do n ot h ave e vidence t hat S tructure 1 w as r epaired a fter t he 1 952 earthquake, but the r econstructed areas did not u se a dobe b ricks o r t apialeras ( figure 5 ). Clay for construction i s r eadily available throughout the village, and a f ew b urrow p its are s till visible. Artifacts such as g lass, charcoal, s eeds, and

1 4

Table S tructure N umber

1 .

S tructures R ecorded

C onstruction Date

D ate When Abandoned

a t T ulor Ayllu.

P resent U se

C ondition R oof Walls

1

1 965

S easonal Dwelling, S torage

I ntact

F ull H eight

4

1 945

N one

S ome L arge H oles

F ull H eight

N one

S ome L arge H oles

F ull H eight

N one

S ome Small H oles

F ull H eight

N one

L argely F allen

5 *

1 800

6

1 975

7

1 820-70

1 929 o r 1 931

N one

8

1 820-70

1 929 o r 1 931

None

9

1 820-70

1 929 o r 1 931

N one

N one

L argely F allen

1 0

1 820-70

1 929 o r 1 931

N one

N one

W all S tubs

1 1

1 820-70

1 929 o r 1 931

N one

I ntact

F ull H eight

1 2**

B efore 1 952

N one

N one

L argely F allen

1 2**, * **

B efore 1 952(?)

N one

I ntact

F ull H eight

1 3***

S torage, S easonal Dwelling

I ntact

F ull H eight

1 4***

S torage

I ntact S mall H oles

F ull H eight

* E vidence o f c onsiderable r ebuilding. * * T hese s tructures s hare a c ommon wall. * ** N o i nformant d ata.

1 5

None

N ear F ull H eight

bone c an b e s een p rotruding f rom walls, s uggesting t hat r efuse was q uarried--perhaps i nadvertently--along w ith t he c lay . B ecause t he t apialera t echnique u ses l ittle w ater, s traw a nd o ther t empering materials a re not n eeded t o r etard s hrinkage o f t he b locks. Moreover, t he c lay i n f act c ontains m uch s and, w hich s erves a s n atural t emper. R oof c onstruction c ommences with p rimary b eams o f Chahar, which are socketed i n or placed upon the t apialeras. Smaller s econdary b eams, a lso u sually C hahar, a re l aid p erpendicularly u pon t he p rimaries a nd b ranches o f L a B rea a re a dded ( figure 6 ). F inally, a l ayer of a dobe ( ca . 1 0-20 cm t hick) i s p laced u pon t he e ntire r oof, making i t water-tight. S traw i s a dded t o make t he r oof a dobe, a nd i ncluded a rtifacts a re c ommon ( figure 7 ). M ost r oofs a re o nly s lightly p itched; t hat o f s tructure 1 2b ( figure 6 ) i s a typically s teep. D ETERIORATION P ROCESSES The d eterioration o f mud-wall s tructures h as b een s tudied i n a n umber o f environments, but i n n one a s a rid a s t he S an P edro d e A tacama. N onetheless, t hese p revious s tudies have i dentified a number of environmental p rocesses t hat a re t o varying d egrees a lso a cting o n t he s tructures o f T ulor Ayllu. E xtant s tudies ( e.g., A gorsah 1 985; H ayden 1 945; McIntosh 1 974; S chiffer 1 987) h ave s hown t hat t hree n on-catastrophic p rocesses c ontribute t o t he g radual d eterioration o f a dobe o r mud-wall s tructures: ( 1) e rosion by r ainfall, ( 2) r ising d amp, a nd ( 3) wood d ecay i n s tructures with wooden members. All o f t hese p rocesses, i t s hould be noted, r equire water. Thus, i n t he S an P edro d e A tacama o ne would i nitially e xpect t hese p rocesses t o p roceed q uite s lowly . T races o f a dditional p rocesses were o bserved, s ome o f t hem c atastrophic, a nd t heir c ontribution t o s tructure deterioration a t T ulor Ayllu i s a lso n oted. T he most o bvious a gent o f s tructure d eterioration i s e rosion by r ainfall. This process has a number of specific e ffects t hat f acilitate i ts i dentification. F irst, a dobe particles a re r emoved f rom e xposed a reas, i ncluding r oofs, walls, a nd wall r emnants. Raindrops t hemselves, s ometimes d riven by s trong winds, c reate smoother t opographies, r ounding a ngular wall j oints a nd e xposed wall s tubs. I n a ddition, d rainage o f particlel aden water s ometimes c auses f urrowing a nd c hanneling, e specially o n r oof margins ( figure 7 ) a nd t he u pper p arts o f walls below p rotruding b eams a nd e specially on walls t hat r eceive r oof d ischarge ( figure 8 ). T he most d ramatic e ffect o f r aindrops a nd r unning water i s t he d ifferential e rosion o f wall material, c aused by v ariation i n a dobe c omposition a nd microtopography, which c reates v ery i rregular s urfaces ( e.g., f igures 2 , 4 , 5 ).

1 6

E rosion a lso l eads t o t he f ormation o f s edimentary d eposits o utside a nd, e ventually, i nside s tructures. F or e xample, when s ediment-laden water, s treaming down the walls, r eaches t he g round, i t s lows down d ramatically, f irst d epositing h eavier p articles n ear t he wall a nd t hen l ighter p articles a t a g reater d istance. T hese f an-like d eposits f orm aprons a round t he o utside o f s tructures ( figure 9 ). I n a ddition, r oofs e ventually develop weak s pots a s t he a dobe i s e roded, a llowing r ainwater t o p ercolate i nto t he s tructure. Weak s pots e xpand i nto h oles which e rode more r apidly, l eading t o t he f ormation o f p oorly s orted s edimentary d eposits o f r oof a dobe a nd L a B rea o n s tructure f loors ( figure 1 0). With t he p assage o f s ufficient t ime, p rocesses of e rosion a nd d eposition will t ransform s tructures i nto a dobe mounds. T he data f rom T ulor Ayllu i ndicate t hat c omplete d eterioration would r equire many, many c enturies i n s uch a n a rid r egion. F or e xample, o ne i nformant r eported t hat t he l oss o f r oof material by e rosion was s o g radual t hat a dobe h ad t o be a dded a t v ery i nfrequent i ntervals--on the o rder of decades. Indeed, a f ew r easonably i ntact r oofs can s till be f ound o n s tructures t hat were a bandoned 4 0 t o 5 0 y ears a go ( figures 7 , 1 0). Thus, a lthough r ainfall e rosion i s the major nonc atastrophic p rocess o f d eterioration a ffecting s tructures a t T ulor Ayllu, i t i s e xtremely s low-acting. A s econd major p rocess o f d eterioration a ffecting a dobe s tructures i s r ising d amp, t he movement o f water by c apillary a ction i nto a wall. The s ubstrate o n which s tructures a re built u sually s upplies t he water, but r ainwater c an a lso p rovide moisture t hat i s t aken up by t he walls. R ising damp c ontributes t o s everal more s pecific destructive p rocesses. The most common i s e xfoliation p romoted by wetting a nd d rying c ycles. C lay e xpands u pon wetting a nd s hrinks when d rying, s etting u p s tresses t hat c ause wall material t o f lake o ff. Another s pecific p rocess f acilitated by r ising damp i s s alt e rosion. This process operates when s oluble s alts c ontained i n a wall--provided by g roundwater, a sh, e tc.-c rystallize o n o r j ust u nder a n evaporative s urface, s palling o ff wall material. B oth p rocesses l ead to e rosion o f t he wall, u sually n ear t he g round, a nd the f ormation of s edimentary d eposits i n t he immediate v icinity . I n s ome cases walls a re s o d eeply undercut by e xfoliation t hat t hey c ollapse o f t heir own weight; t hey a lso b ecome much more s uceptible t o b eing k nocked d own by earthquakes ( or even vandals). Rising damp is s urprisingly c ommon i n a rid l ands, p erhaps e xacerbated by t he h igher water t ables b rought a bout by c anal i rrigation. The e ffects o f r ising damp were s een o n many walls a t T ulor Ayllu, a lthough d amage was e xtreme i n j ust o ne o r t wo c ases ( on s tanding w alls). U ndercutting a nd e longated

1 7

c raters a long t he base o f t he wall a re t he u nequivocal s igns o f t his p rocess ( figure 1 1). On t he basis o f o ur c ursory e xamination, l ittle e vidence o f s alt c rystals was f ound i n t he e xfoliated a reas, s uggesting t hat wet-dry c ycling--not s alt e rosion--was t he d ominant d eterioration p rocess. R ising d amp p robably c aused h igher r ates of material l oss i n t he p ast, when the i rrigation system a t T ulor Ayllu was i n more r egular u se. I ndeed, s ome o f t he o lder täpiäleIA s tructures s how s erious u ndercutting ( figure 1 1); t he most badly weakened walls p robably c ollapsed when e arthquakes s truck ( see b elow ). We s uspect t hat t oday r ising d amp i s o perating v ery s lowly. A t hird major p rocess o f d eterioration i s wood d ecay ( for a s ummary o f t hese p rocesses, s ee S chiffer 1 986, 1 987). T ermites, f ungi, a nd beetles o rdinarily a re the most d estructive d ecay a gents f or u nburied wood i n a rid l ands. Wood o n t he g round a nd i n t he r oofs o f s tructures a t T ulor Ayllu was i nspected f or t he t races o f wood r ot, a nd t he f indings were a lmost c ompletely n egative. With t he e xception o f a small p iece o f C hahar w ith b rown r ot f ound o n t he g round, no o ther evidence o f ( organic) wood d ecay was o bserved. H owever, a t t imes i t w as d ifficult t o i nspect wood i n r oofs, a nd s o s ome f ungal r ot c ould h ave b een missed. E ven s o, t he near a bsence o f moisture g uarantees t hat a ny f ungal r ot i n r oof materials w ould b e p roceeding a t a g lacial p ace. Weathering a lso c ontributes t o wood decay . This p rocess r equires d irect s unlight, o f which t here i s no l ack i n t he S an P edro de Atacama a rea, a nd water. The t elltale g rey c olor a nd c racking o n b eam e nds t hat t ypify weathering were f ound o n a ll e xposed wood. T he most v ulnerable wood i n t hese s tructures i s t he t hin b ranches a nd twigs o f L a B rea i n t he r oof; a fter t hese a re e xposed by e rosion o f t he a dobe capping, t hey become b rittle and f all or are washed i nto the s tructure. Overall, weathering r educes wood mass a t a v ery s low r ate, o n the o rder o f millimeters p er c entury. Thus, u nburied wood, which i s mainly a ffected b y w eathering, s hould l ast many c enturies--perhaps millenia--in t his e nvironment. I n c omparison t o a dobe s tructures i n more mesic r egions, t hose a t T ulor Ayllu a re l ittle a ffected by p rocesses of w ood d ecay. I n a ddition t o t he c ommon p rocesses o f e rosion, r ising d amp, a nd wood d ecay, s everal o ther s low-acting p rocesses--principally p lant g rowth a nd e olian a ction--are c ontributing t o t he d eterioration o f s tructures i n t he S an P edro d e A tacama a rea. P lant g rowth s ometimes c ommences i nside a s tructure a fter t he r oof i s g one. S hrubs were o bserved i n s everal s tructures with l ow o r c ollapsed walls ( figure 1 2), but p lants w ere l acking i n many o ther c omparable s tructures.

1 8

P lants w ould h elp t o a ttract e olian d eposition o f mineral particles a s well a s o rganic matter, perhaps s lightly accelerating the r ate of deposit formation within s tructures. L eaf l itter f rom t rees a ssociated with s tructures a lso c ontributes t o s edimentary d eposition n ear t he walls, where o ne s ometimes f inds a lternating l enses o f o rganic a nd mineral matter. O verall, v egetation p lays a s mall r ole i n s tructural d eterioration a t T ulor Ayllu. D espite t he i mposing p resence o f t he c reeping s and d une, e olian p rocesses s o f ar have h ad l ittle e ffect on T ulor Ayllu p roper, b ut t hey a re i mportant r egionally a nd w ill e ventually b ring a bout major t ransformations a t T ulor Ayllu. The many Chahar t rees a s well a s t he dune i tself p rotect t he s tructures i n T ulor Ayllu f rom s and b lasting a nd e olian d eposition. On t he o ther s ide o f t he d une a t T ulor A ldea, h owever, e olian p rocesses s eemingly d ominate t he a rchaeological r ecord. Not o nly i s s tructure f ill mainly e olian s and, but e xposed a dobe walls a re being s ignificantly e roded by s and-blasting. O ne must k eep i n m ind, t hen, t hat a s t he s and d une p asses o ver T ulor Ayllu, e olian p rocesses will become c entral, a s t hey now a re a t T ulor A ldea ( cf. S chiffer 1 987: 2 43-245). I t s hould be n oted, t hough, t hat t he s and dune h as a lready begun covering some f ields ( figure 1 ) and i s immediately t hreatening a t l east o ne s tructure. A n a ppreciation f or t hese n on-catastrophic p rocesses permits us to s ketch a general scenario for the d eterioration o f a dobe s tructures i n the S an P edro de Ataca ma region, which might be applicable to e nvironmentally s imiliar r egions. T he i nformant d ata a nd o bservational e vidence s uggest, o verall, t hat s tructures d eteriorate a t a r ather s low r ate. E rosion o f r oof and wall material becomes noticeable a fter s everal d ecades, but does not s eriously d egrade t he i ntegrity o f the s tructure. The r avages o f r ising damp a re a lso v isible w ithin d ecades, b ut i n t hick-wall s tructures t his p rocess i s not immediately threatening. P robably within a c entury, t he e rosion o f r oof materials--if u nrepaired-r enders a s tructure u ninhabitable. E ven s o, p rimary b eams may s till be l argely i ntact a nd i n p lace, a nd t he walls will be s tanding t o n ear o riginal h eight. Appreciable d amage t o t he walls a nd c ollapse o f t he r oof r emnants--the r esults o f f urther e rosion a nd r ising d amp--probably would n ot t ake p lace u ntil t he s econd o r t hird c entury a fter c onstruction. T he f ormation o f a n a dobe mound, i n which n o wall r emnants c ould b e o bserved o n t he s urface, would a ppear t o r equire many more c enturies. The l eisurely p ace o f t hese s low-acting p rocesses p rovides ample opportunity f or o ther p rocesses--of a c atastrophic n ature--to e xert a n a ppreciable i nfluence o n a ctual s equences o f s tructural decay. I ndeed, a t T ulor Ayllu t oday o ne c an o bserve many s everely d eteriorated

1 9

s tructures, b uilt w ithin t he l ast two c enturies, t hat must have b een a ffected by o ther p rocesses because t he s lowa cting p rocesses a lone c ould not have b rought about s uch s evere t ransformations. Two major c atastrophic p rocesses were pinpointed by our infor mants: ( 1) r azing of s tructures a ssociated with t he typhoid epidemic and ( 2) e arthquakes. I t was r eported that s tructures 7 , 8 , a nd 1 0 h ad b een b urned b y t he military a fter t heir a bandonment d uring t he 1 931 typhoid epidemic. As c an b e s een i n t able 1 a nd f igures 9 , 1 1, 1 2, a nd 1 3, t hese s tructures a ll l ack r oofs and wall h eights a re variable. This marked variation i n wall p reservation i s s omewhat puzzling. I n p articular, t he walls o f s tructure 1 0 ( figure 1 2) a re u niformly v ery P ossibly these walls were pushed down- or c ollapsed--as part o f t he d estruction p rocess. I n t he c ases o f s tructures 7 , 8 and 9 , walls a re o f variable height, b ut a ll have a t l east a small r emnant t hat i s nearly f ull height. Earthquakes might have been r esponsible f or t his p attern o f d ifferential wall c ollapse ( see, e specially, f igure 1 3). I n any e vent, t he c ultural a ctivity o f s tructure b urning has c learly a ltered t he c ourse o f d eterioration f or s everal s tructures, c ausing collapse of the roofs and vastly accelerating the d eterioration o f t he w alls. S everal s tructures were i dentified by i nformants a s having suffered earthquake damage. The r epair of s tructure 1 a fter an e arthquake i n 1 952 h as a lready b een m entioned ( figure 5 ). S tructure 1 2a was s aid t o h ave b een a bandoned p rior t o i ts c ollapse i n t hat s ame e arthquake ( figure 1 4). I n a ddition, we s uspect t hat s tructures 7 , 8 , a nd 9 , which a lready l acked r oofs a t t he t ime o f t he 1 952 e arthquake, were s omewhat d amaged by t his t emblQi . ( and perhaps earlier ones). B ecause e arthquakes o ccur o ften i n t his a rea, o ne c an e xpect many o f t he r emaining s tructures to s uffer e arthquake damage i n t he f uture ( before t hey a re c ompletely c overed b y t he s and d une). Together, t he c atastrophic p rocesses o f s tructure b urning a nd e arthquakes h ave a ccelerated t he d estruction o f a n umber o f s tructures a t T ulor Ayllu, l eading t o wall c ollapse t hat o therwise w ould n ot h ave t aken p lace. One s emi-catastrophic p rocess that we did n ot document i s s cavenging o r c ollecting o f wood f rom t he r oofs . I ntact r oofs, e ven o n s tructures a bandoned s everal d ecades a go, s uggest t he a bsence o f t his p rocess; t his i s s urprising i n view o f t he p otential u tility o f t his wood r esource i n s uch a n a rid l and . P erhaps s cavenging h as n ot t aken p lace b ecause t he small r esident p opulation o f T ulor Ayllu c an meet i ts wood n eed without h aving t o t ear d own r oofs. A lso, T ulor Ayllu i s s omewhat r emote, a nd t hat may d iscourage c ollecting. F inally, we n ote t hat a lthough

2 0

a bandoned i n a n a rchaeological s ense, t hese s tructures a re s till s ubject t o c laims o f ownership by f ormer o ccupants ( or their r elatives) who l ive i n nearby ayllus. Thus, r espect f or p roperty r ights may deter s cavenging and c ollecting. C ONCLUSION L ike many a bandoned o r n early a bandoned s ettlements, T ulor Ayllu i s a n atural l aboratory f or s tudying p rocesses of structural deterioration. The availability of i nformants has a llowed us to gain s ome appreciation for t he t empo of d eterioration processes i n this very a rid e nvironment. When u naffected by c atastrophic p rocesses, adobe s tructures at Tulor Ayllu decay very s lowly, being a ffected mainly by e rosion and r ising damp. H owever, c atastrophic p rocesses--burning o f s tructures f ollowing a typhoid epidemic and earthquakes--have appreciably i nfluenced t he d eterioration o f many s tructures. I n more mesic environments, where the uselife of an adobe s tructure i s s horter a nd where n on-catastrophic p rocesses t ransfor m structures more rapidly, there i s less opportunity f or catastrophic processes to i nfluence structural decay. In the future, archaeologists e xcavating t he r emains o f a dobe s tructures s hould c onsider t he mix o f c atastrophic and non-catastrophic p rocesses t hat l ikely operated i n particular r egions. ACKNOWLEDGMENTS The f ield work a t Tulor Ayllu was c arried out as part of t he T ulor A ldea P roject, s upported i n 1 985 by t he S ociedad de Arte P recolombino, Santiago. Participation of the senior author i n this season of fieldwork was made p ossible by a g rant f or a s hort-term v isit f rom t he L atin American P rogram o f t he N ational S cience F oundation. We o ffer warmest t hanks t o o ur i nformants, S egundino Mamani, Maria O ssande ln, L eonardo Reyes, F rancisco Reyes, and F rancisco T ejerina.

2 1

F igure

1 .

T he

s and

f ield

F igure

2 .

i n

T apiAlera

d une

e ncroaching

T ulor

u pon

a n

a gricultural

Ayllu.

c onstruction

2 2

( structure

1 4).

F igure

3 .

F igure

A dobe

4 .

b rick

c onstruction

( structure

Hybrid construction of adobe t apialeras ( structure 5 ).

2 3

4 ).

bricks' and

F igure

5 .

F igure

U pper h alf o f f acing ( structure 1 ).

6 .

wall

h as

D etails o f r oof c onstruction i nterior o f s tructure 1 2b.

2 4

been

a re

r epaired

v isible

i n t he

F igure

F igure

7 .

8 .

R oof

o f

s tructure

1 1

( note

The r ear of s tructure 1 1 w alls f rom r oof r unoff.

2 5

s herd

shows

n ear

r ear).

f urrowing

of

F igure

9 .

F ormation a djacent

Figure

10.

of t o

f an-like

e xterior

s edimentary

w alls

S edimentary d eposit o n t he b elow h oles i n r oof.

2 6

o f

deposits

s tructure

f loor

8 .

o f s tructure

4

F igure

1 1.

U ndercutting c aused by r ising d amp c an b e a t t he b ase o f t his w all ( structure 9 ).

F igure

1 2.

P lants g rowing i n s tructure i n t he b ackground).

2 7

1 0

( structure

s een

1 1

i s

F igure

1 3.

S tructure e pidemic

7 o f

was

burned

a fter

t he

typhoid

1 931.


1 )

.0 C I M r"

. 1 . > in L i) .- .. ( . . 4

1 : J • 4 .) . ij t i w • • • , c •H up I . C Z • 2 0 C L ) •H . . . •H W

•. I

•

. . , . , -, _ „ . J , _ , 4 u . r ) ,z u . 0 0 , _ , c u . i . i • " i C D Z

4 . 4 4 . )

,

C L) c z

C V W

a ) , . , . H

, 4 C V 4 . )

. G ) -

E

C . )

n t 2

u,

G J I

c l )

( 1: 1

c

0

c . a ) c o , 4

I . 0 )

W

0 t 2 . • , • ( C L ( r 3

0

0

. .

c u

a )

I .

M

,. 1

a )

C I )

0

CD

C2 .

C a E .

X • ' " , G ) I n

4 )

c r )

0 . , . 4

C . ) C C . )

C U . . )

C I )

c d

C

• . 1

C > -1 G . : I 1 . • C . 1 r i

C a . . )

C • . 1 2 0 I . U " )

C D ( I ) I . 1 : 1

X G . )

. , L 4 • 3 1 -

C . / . 0 h . > , ^ . . . ••, . J 1. . -t r , r : • • • • • . . 'V • • • • . C r d "C C • t : : E G ., C J C l i . . , . . L . E r ., 0 0 . . . . 0 ‘ . i . "0 0 G C 0 0 G . , G 1 C ) C ." - r n c . ) . . r e -7 0 . . 4 b . • ' > , } . C I ) .1 E l .Z Z

C U

r z .

CO

-0 > , ID 0 . 1 • " , I 1 / 4 .1 . 4 . 4 .. c 0 4 - .0

1 . . .

a ) r e , =

"I

.0

. • el

o l : C . . 4 0 C U C ) k ) • u. •• • • = G J • • • C J ' 1 C C . .7 i . I : r d 4 4 17 c r : . • • • 0 1" C

. 0 0 ) . . . . 1, 0 . • E . C r : • 0 O L L a A -, " . C Z C > , U : L 3 . 1 : c r . 1 . . I ' D 4 : - a) " E G I 1 ., G , • 1 , . . r .. .7 4 C c . . » , C l ) • • • E 0 . . 2 C . X ` ' E .. C l )

•