Palaeoenvironmental Investigations: Research Design, Methods and Data Analysis 9780860543305, 9781407341866

Table of contents :
Copyright Page
Contents
Editorial Notes
Clastic sedimentation in the phreatic cave environment
An examination of the zonal model of sedimentation in caves
The role of mineral magnetic measurements in archaeology
Early mining in Britain: the stratigraphic implications of heavy metals in alluvial sediments
Stable carbon isotope analysis of anthropogenic soils and sediments in Orkney
Molluscan taphonomy in braided river environments: model development and application to the Summertown-Radley Terrace Gravels of the River Thames
Studies of archaeological soils and deposits by microphological techniques
Amino acids in buried soils
Truncated skew log laPlace distributions and particle size analysis
Missing information and collections of skeletal material
“Great things from little acorns…”: a suite of programs for the analysis and representation of palynological data using the BBC micro
On the presentation of results in environmental archaeology
Species composition parameters and life tables; their application to detect environmental change in fossil land molluscan assemblages
Carbonised seeds, sample size and on-site sampling
Geomorphology and settlement studies in archaeology
Ecological investigations of marine molluscs: an examination of changes in body weight and shape as aids to the interpretation of the mesolithic shell middens of the island of Oronsay, Inner Hebrides
Macro- and micro-level approaches to the reconstruction of palaeoshorelines
Erratic palynomorphs and palaeolithic stratigraphy
An estimate of avalanche frequency in Glen Feshie, Scotland, using tree rings
Relating fen edge sediments, stratigraphy and archaeology near Billingborough, South Lincolnshire
Index 1. Subjects
Index 2. Biological taxa
Index 3. Locations and people

Citation preview

Palaeoenvironmental Investigations Research Design, Methods and Data Analysis edited by N. R. J. Fieller, D. D. Gilbertson and N. G. A. Ralph

Symposia of the Association for Environmental Archaeology No. SA

BAR International Series 258 1985

B.A.R. 5, Centremead, Osney Mead, Oxford OX2 0ES, England.

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

B.A.R.-s258, 1985: 'Palaeoenvironmental Investigations: Research Design, Methods and Interpretation' © The Individual Authors, 1985

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 9780860543305 paperback ISBN 9781407341866 e-book DOI https://doi.org/10.30861/9780860543305 A catalogue record for this book is available from the British Library This book is available at www.barpublishing.com

Palaeoenvironaental Investi gations: Research Design, Methods and Interpretation. edited by N.R.J. Fieller, D.D. Gilbertson and N.G.A. Ralph (Univer sity of Sheffield , Sheffiel d , SlO 2TN , UK. )

Associ ati on f or Environmental Archaeology Syaposiua 5(i) held at Stephenson

Hall~

University of Sheffield

September 1983

CONTENTS

Page

N.R.J. Fieller, D.D. Gilbertson and N.G.A. Ralph . Editorial notes

1

Sediaents

S.J. Gale .

Clastic sedimentation in the phreatic cave environment.

5

C.M. Griffin . An examination of the zonal model of sedimentation in caves.

21

F. Oldfield , A. Krawiecki, B. Maher , J . J . Taylor and S. Twigger . The role of mineral magnetic measurements in archaeology .

29

M.G . Macklin, S.B. Bradley and C.O . Hunt. Early mining in Britain: the stratigraphic implications of heavy metals in alluvial sediments .

45

Stable carbon isotope analysis of I . A. Simpson . anthropogenic soils and s ediments in Orkney.

55

D.J. Briggs, D. D. Gilbertson and A. Lynda Harris. Molluscan taphonomy in braided river environments: model development and application to the Summeretown-Radley Terrace Gravels of the River Thames.

67

Soils

P.F. Fisher and R.I . Macphail . Studies of archaeological soils and deposits by microphological techniques . J. Beavis.

Amino acids in buried soils.

92 113

Statistical Methods

N. R.J. Fieller, D.D . Gilbertson, W. Olbricht and D.A.Y. Timmins . Truncated skew l og laPlace distributions and particl e size analysis.

127

S.W. Hillson. Missing information and collections of skeletal material .

137

i

Page

M. V. And r ews . "Great things from little acorns • •• ": a suite of programs for the analysis and presentation of palynolog i cal data using the BBC micro.

143

T. P. O' Connor. On the presentation of results in environmental archaeology.

147

D. Gordon and Caroline Ellis. Species composition parameters and life tables: their application to detect envir onmental change in fossil l and molluscan assemblages.

153

M. van der Veen. Carbonised seeds, sample size and on-site sampling.

165

Past envi ronments , ge omorphology and s ettl ements

N.M. Mill s . Geomorphology and settlement studies in archaeology .

175

D. A. Jones . Ecological investigations of mari ne molluscs: an examination of changes in body weight and shape as aids to the interpretation of the mesolithic shell middens of the isl and of Oronsay, Inner Hebrides .

209

J.C. Shackleton . Macro- and micro-level approaches to the reconstructi on of pal aeoshor elines .

221

C. O. Hunt .

Erratic palynomorphs and palaeolithic stratigraphy.

229

R.G . W. Ward . An estimate of avalanche frequency in Glen Feshie , Scotland, using tree rings .

237

P . P. Hayes. Relating fen edge sediments, stratigraphy and archaeology near Billingborough, South Lincolnshire .

245

Index 1.

Subjects

261

Index 2.

Biological taxa

283

Index 3 .

Locations and people

285

ii

PALAE OENVIRONMENTAL INVESTIGATIONS:

EDITORIAL NOTES

The 5th Annual Symposium of the Association for E nvironmental Archaeology was held at the University of Sheffield in September 1983. The conference was attended by well over 100 people. It had the inter-related themes of research design, research methods and interpretation. The topics discussed focussed on two subjects which we have termed "Palaeoenvironmental Investigations" and "Palaeobiological Investigations". These form the titles of the two symposia volumes S(i) and S(ii) which record the proceedings of this conference. The emphasis on "investigation" is especially important in the development of the subject at this moment in time. In Karl Butzer's new book (1982) Archaeology as Human Ecology, Cambridge: Cambridge University Press, we have the first of a new generation of texts which emphasize the nature and development of conceptual models in environmental archaeology. The testing and elaboration of these models will only be achieved by investigation in which the skills of research design, methods and data analysis will be paramount. In this day and age the academic and non-academic world s are increasingly beset with questions of style, and guarantees of excellence. We wish to place on record the following information which concern the research papers in this volume. Every published paper has been subject to peer group review. Each paper has been scrutinised by two referees of international or national standing, and has also been read by an "inf ormed reader" - usually a Sheffield post-graduate - as well as the editors. These two symposlum volumes have. also presented major technical challenges to us. We have endeavoured to use the " new technologies" in their production, evidence of which is illustrated by the computer-generated set of indices. Several papers have been received in the form of magnetic tape or floppy disk. Unhappily, the other new computer technologies have failed to resolve problems of protocol and compatability. Consequently very difficult typing and re-typing tasks have fallen upon Miss Val Kinsler and Ms. Betty Gowland, who have coped admirably under difficult circumstances. Fortunately, the frustrations and production delays experienced have not affected the publication date of these volumes. This is because we did not receive the final corrected proofs from three contributors ( who shall remain nameless) until mid-January 1985. Our best efforts were clearly of little avail. The management and success of the Sheffield conference owed much to the courtesy of the staff of Stephenson Hall of the University of Sheffield and Ms. C.M. Griffin, Ms. M.V. Andrews, Mr Geraint Coles and Dr. C.O. Hunt, who assisted admirably with both administration and conference delegate management.

1

The field trip to the caves and magnificent Visitor Centre at Creswell Cr ags was a great success and we would like to record our gratitude to t he Senior Ranger , Dr . R. D. S. Jenkinson , his staff and the County Councils of Nottinghamshire and Derbyshi re . \

Professor V. D. Barnett kindly made ava i lable wo rd processing facilities and support in the Department of Probability and Statist i cs of the University of Sheffield .

D. D. Gilbertson and N. G. A. Ralph Department of Archaeology and Prehistory University of Sheffield Sheffield SlO 2TN

N.R. J . Fieller Department of Probability and Statistics Unive rsity of Sheffield Sheffield SlO 2TN

February 27th, 1985

2

SEDIMENTS

3

ClASTIC SKDIKKRTATI OH Ill THE PIIRFATIC CAVE KHVIllOHMKHT

Stephen J. Gale Jesus College Oxford OXl 3DW United Kingdom

ABSTRACT

Cave deposits have been widely used in palaeoenvironmental studies. these studies have often been based on an inadequate Unfo rtunately, knowledge of the unique sedimentary processes at wor k in caves. The especially poorl y are sedimentation phreatic of processes understood, and yet the phreas c onstitutes p r obably the most distinctive cave depositional environment. In order to clarify the mechanisms of cave sedimentation, this study therefore considers three particlar aspects of phreatic sedimentology : clast shape, sedimentary structure and sediment texture.

Despite previous suggestions that sedimentary particles eroded and conditions possess a distinctive phreatic under transported morphology, this study finds no evidence to support this and concludes that trends of changes in particle shape are similar to those observed in other hydraulic systems. By contrast , a unique mode of sediment transpor t , the sliding- bed, seems to occur under phreatic conditions. This gives rise to distinctive sedimentary structures and sediment textures, which may enabl e fossil phreaticdeposits to be identified. The hydraulic conditions under whic h sliding-beds develop are discussed, and it is shown that inferences may be drawn about the conditions of sediment transport and deposition from studies of fossil phreatic cave-sediments.

In Fieller , N. R. J . , Gilbertson, D.D . and Ralph, N.G . A. 1985

Pa lae oenvi ronaental Investi gat i ons: llesear ch Design~ Methods and Data Analysi s. Symposium number S(i) of the Association for Environmental Archaeology. Oxford : British Archaeological Reports International Series. 5

SYMBOLS

a

Sedimentary-particle long-axis.

b

Sedimentary-particle intermediate-axis.

c

Sedimentary-particle short-axis.

D

Sedimentary-particle diameter.

D

Mean sedimentary-particle diameter .

Dso

Median sedimentary-particle diameter.

d

Diameter of cond uit.

Fe

Dimensionless ratio in Durand correlation; a function of sedimentary-particle diamet er and delivered concentration of solids; for D

1,

2 mm , Fe

1.33

;v

g

Gravitational acceleration

R

Hydraulic radius of conduit

Reo

Sedimentary-particle Reynolds number

S

Slope of conduit energy-grade line .

-u

Mear. flow-velocity.

ucrit Critical flow-velocity at which sliding-bed movement ceases u* ~

Boundary shear-velocity Fluid kinematic viscosity

JO£

Fluid density

f' s

Sedimentary-particle density

J'

~P

Shear-intensity parameter Maximum-projection sphericity index .

6

INTRODUCTION

The behaviour of caves as sediment traps and their ability to preserve long sequences of deposits away f r om the effects of subaerial erosion make them unique amongst terrestrial sedimentary environments. As a result, cave deposits have frequently been used in efforts to elucidate the long-term environmental histo r y of an area, particularly since deposition in caves takes place under c onditions which reflect to some extent those of the prevailing surface environment . Such investigations c l early necessitate an understanding of the processes of cave sedimentation. Yet this has often been inadequate, especially since many of the transport and depositional processes at work in the cave environment seem to be unique. As a consequence, environmental reconstructions based on the c ave sedimentary record have either had to be somewhat speculative, or have relied upon the use of surface analogues for cave sedimentation processes. Both approaches can only lead to misinterpretation.

It is proposed to consider here only the sedimentary processes whic h occ ur within phreatic caves. The phreas constitutes probably the most distinctive cave depositional environment, and yet the one about which least is known. This is largely because of the hazardous na ture of active phreatic passages, access to which can only be o btained under conditions of considerable risk. As a result, f e w observations have been made in phreatic caves . Nevertheless, the r e are several reasons why sedimentary processes in the phreas ma y differ from those found elsewhere. The invariate channel boundaries and the full-pipe flows that occur in phreatic cond uits give rise to distinctive suite of hydraulic conditions; the absence of subaeria l erosion means that, once deposited, sediments are not so easily eroded or reworked by slope wash and similar processes; and the lac k of a protective vegetation cover means that sediments are mo r e s usceptible to eros ion by channel f.low processes.

The aims of this study are therefore to attempt to clarify t he mech a nisms of clastic sedimentation in the phreatic environment, t o dis c uss the sedimentological features resulting from phreatic s e dimentation, and to consider whether any inferences can be made about the conditions under which phreatic sediments were transported and deposited . Three particular aspects of phrea t ic sedimentology are considered: clast shape, sedimentary structure and sediment texture.

THE HYDRAULICS OF PHREATIC FLOWS

Phreatic flows take place under fu l l-pipe condition s , and henc e almost invariably under conditions of pressure flow. Studies of the hydrauli cs of phreatic flows during high discharges (Gale 1984 , and unpub.) have shown that, although all the sites investigated

7

experienced flows within the turbulent-subcritical regime, flows in different conduits took place under a wide range of hydraulic condition~ 1 Thus, mean boundary-shear stresses varied between~0.01 and"'2 N m , Darcy-Weisbach friction factors between... 0.07 and-0 .17, boundary_ roughnesses -~etweenk50 andN500 mm and flow powers between 3 NQ.5 x 10 and... 0.5 W m . Nevertheless, i t is suggested that, within any given phreatic system , discharge, and hence all other hydraulic parameters, does not vary over time as widely as in other hydraulic systems. This is because, in any individual phreatic conduit , highdischarge flows reach a single maximum value whose magnitude is governed by the geometry of the flow system, its boundary friction and its hydraulic gradient. Since , in a bedrock channel, neither hydraulic geometry nor boundary friction vary appreciably over time, and since hydraulic gradient will rarely increase above a certain value at which wa t e r backing up the cave system will tend either t o pass into bank storage in the fracture zone around the conduit or to overflow into a higher-level conduit, then a maximum discharge value will exist within each system. This thesis is borne out by an investigation of a number of long-term karst-spring hydrogra phs which charac teristically display a pl ateau-like form of discharge maxima (see, for example, Bassett 1976 , and Smart and Ford 1983).

THE MORPHOLOGY OF SEDIMENTARY PARTICLES UNDER CONDITIONS OF PHREATIC TRANSPORT It has been sugge sted by several workers that sedimentary particles eroded and transported under phreatic conditions posses a distinctive morphology which is the result of the existence of unique erosional processes at work in the phreatic zone . If this hypothesis could be shown to be correct , it would provide a powerful means of identifying fossil phreatic deposits and would give considerable insight into the processes of phreatic erosion and sediment transport. Amongst the ear·liest work in this field was that of Bravard and Siffre (1958) who found cave pebbles to be characte rised by high indices of flatness and roundness. The existence of high indices of cave-pebble flatness was apparently borne out by the work of Sweeting (1972: 174) in Boreham Cave, northwest Yorkshire. Siffre (1959) regarded the flat pebbles as the product of cavitation of the walls of phreatic conduits at points where constrictions caused an increase in flow velocity and a dec rease in pressure (Siffre 1959; Siffre and Siffre 1961). Subsequently, however, it was concluded that the relative flatness of cave-stream pebbles could be a function of a number of other variables, including the petrography, density and fracturing of the parent rock, and that, instead, phreatic pebbles could be characterised by their highly-rounded shape (Siffre and Siffre 1961). The rounding of the pebbles was attributed to their abrasion by sands in suspension; this took place at constrictions in phreatic conduits, at which points flow-acceleration and , presumably, high abrasion were considered to occur (Siffre 1959; Siffre and Siffre 1961).

8

Recent work by Gale and Page (unpub.ms) has sought to clarify this question by investigating sediments in the active phreatic passages of Dan yr Ogof I in the Upper Tawe Valley, south Wales (Figs. 1 and 2). This study consider ed only pebbles of Upper Carboniferous Sandstone, known to have been derived from upstream of the sampling sites ; only pebbles being actively transported through the phreatic zone; and, to eliminate the variable of particle size, which Sneed and F'o lk ( 1958) have shown to be one of the most important controls on par ticle shape, only pebbles of a limited size range (long-axis = 30-50 mm). In order to obtain an indication of the shape of the Upper Carboniferous Sandstone pebbles prior to their incorporat ion in the stream load, samples of pebbles within the same size range were also taken from the surface closed depressions which constitute the major hydrological inlets to the Dan yr Ogof system: Sink y Giedd and Waen Fignen Felen (Fig.1). 2 The study showed that mean particle-sphericity p

cm

JU s ltu shvs t11 1 de9ru of reauu t ••~•ttlsatlu

ltctwud U tilt hlthl hn.erd fhld

m CORE I

r

r

-•oml

lh!t

u .. ,,..,,

1 I I ·~·· ···

vil GLm~SER·~THR ) VAL.~LEU"~LYS·~PRO.HHE.HLE ) ARG~HIS~MET~TYR~CYS.

This pattern is similar to those summarised by Stevenson(1982,93), when calculated on the same basis. To see if more closel y matched groups could be detected within this broad similarity , concentrations of amino acids were treated as as multivariate data set for each horizon . Logarithms of the replicate means were taken, and these expresses as residuals about the mean logarithms for each horizon, to avoid unpredictable influences of extreme values in subsequent analyses, and to eliminate the variation due to differences in absolute concentration. Data were then subjected t o principal coordinates analysis. Single linkage cluster analysis was used to provide a minimum spanning tree, and an agglomerative dendrogram. Euclidian distance was use d throughout, and the routine drawn from GENSTAT (Version 4.03, Numerical Algorithms,l980). Locations of soil horizons are plotted in relation to the first two dimensions computed by principal coordinates analysis in Fig.11 . The variance accounted for by the first two dimensions is 48%. There

119

appear to be two distinct clusters, but the validity of these cannot be assumed from appearance . The assumption can be strengthe ned by testing whether nearest neighbours in the minimum spanning t r ee lie within the same clusters (Everi tt,l978,36). The minimum spanning tree is superimposed on the scatter graph in Fig . ll, and it can be seen from the similarity indices shown on the representation of the minimum spanning tree in Fig.l2, that, with the exception of HM77F6(5)bAh, similarities within clusters are greater than the simila r ity between them. Two main clusters and the sepa ration of HM77F6(5)bAh 3re shown in the dendrogram , Fig . l3, which lists the groups of horizons contained in the two clusters . The distinction between clusters has since been confi r med by multivariate anal ysis of variance . Wilks' Lamda = 0 .1799, and using the transformations described by Chatfield and Collins (1980,148- 9) this approximates to chi-squa r ed = 59.18, which is significant at p(O . OOl. of horizons s urface predominantly Members of Group 1 are contemporary and buried soils ; Group 2 contains mainly s ubsoil were Group each horizons. Mean relative concentrations for to compare the Fig . l4 in plotted are These calcul ated . c haracteristic pattern of surface and subsurface compositions. Student's T tests confirm that Group 2 (subsoil) horizons are depleted in SER, PRO, ALA, VAL, LEU, and PHE, and enhanced in GLU, MET, and LYS with respect to Group 1 (surface) horizons: p(O.OOl except for LYS when p) O.OOl 1983 ** 5 REM** ** 6 REM** M.V. Andrews ** 7 REM** & ** 8 REM** M.C . Bishop ** 9 REM*** ********~************•******** 20 ONE:.RROR l~ERR-= 17fHENGOT04ll E:.LSE IFERR=2 14 THENPROCNO EL SE PROCerror 3 0 *FX18 4 0 CLEAR:MODE7:PROCME.NU:PROCINPUT: PROCI NIT 5 0 MODEO:VDU19.0.7;0;t9.1.0;0; 60 PROCscale:PROCabsolu~e· 70 REPEAT:PROCwatt:UNTILFALSE 8 0 END 90 DEFPHOt.:wa.1t 100 REPEAT UNTIL INI OR INI 160 *FX15.0 170 CLS:PRINl TAB "Enter the ·filename of";TAB ; "t he species you require":*FX21.0 · 180 INPUTTAB "s 1•;TAB 1983 ** 5 REM** ** 6 REM** M.V. Andrews ** 7 REM** & ** 8 REM** M. C. Bi s hop ** 9 REM************************** ******* 20 ONERRORIFERR=17THENGOT040 ELSEIFERR=214 THENPROCNO ELSE PROCerror 30 *FX18 40 CLEAR:MODE7:PROCMENU:PROCINPUT: PROCINIT 50 MODEO:VDU19 ,0.7; 0;19,1,0;0 ; 60 PROCpercent:PROCscale 70 REPEAT:PROCwait:UNTILFALSE:END 80 DEFPROCwait:REPEAT UNTIL INKEY- 116:*FX21 .0 90 IF INKEY-1 16 THEN PROCASSEMBLE:VDU2:CALLtYOUR SCREEN DU MPJ:VDU3 100 ENDPROC 110 DEFPROCINPUT :DIM AC1l:*FX21,0 120 CLS:PRINTTAB Onlr u se lines 100 10 to 1026 0 REM[ 2 ) In i n e 10 030 P%=&1 100 REM[ 3 ) In li ne 1004 0 LDA# &3 s houl d read LDA#print% REM[ REM[4) Li ne 10240 should read . End REM[ LDA# 27:JSRPrinter:LDA#64:JSR REM[ Pr inter:RTS REM REM ENDPROC

6 10 DEFPROCdrawpol l 6 2 0 FORpoll%=1 TO A< 1 > 6 30 IFC =0 THEN 650 6 40 MOVEdept h 7. ,tli n e7.-4:DRAW dept h %, tl i n e%- 4g shell weight) . Vertical bars rep r esent standard error.

50

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I \ I

40

\

I I

I

,

\

,r

I

I

I

I

~

, \

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\

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20

,

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30

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:;/·

10

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/ ,/ ·~.,

1

2

3

4

5

6

7

8

modern low shore modern high shore midden

-

length 1 height

1 - .:::: 1·49 2 : 1·5-1 · 99 3 = 2·0- 2·49 4 - 2 ·5- 2·99 - 3·0 - 3·49 5 6 - 3 ·5 - 3·99 7 -- 4·0- 4·49 8 - ..... 4·5 ~ FIGURE 10). THE DISTRIBUTION OF DIFFERENT SHAPED LIMPETS IN THE MIDDENS COMPARED TO THE MODERN SHORE·

MACRO- AND MICRO-LEVEL APPROACHES P.ALAEOSBORELINES

TO

THE RECONSTRUCTION OF

.c. Shackleton Associate Clare Hall Cambridge

J

ABSTRACT It is suggested that, not infrequently, archaeologists unde r estimate the nature and impact of the effects of changes in sea level ( due to alternating periods of glaciation and deglaciation) on the r e sources that were available to prehistoric man. The problem is explored at two levels: the macro scale of the circum- Mediterranean region and t he micro scale of a specific site, Franchthi Cave, Greece . It is shown that topographic consequences are felt unequally, the type of land gained or lost may be more important than its area, and the influence of a rising sea level may be felt· over a much larger r egion than is often realised. Changes in the resource base available to prehistoric people can also be monitored on the micro scale. The example used of shellfish exploitation at Franchthi demonstrates that one can estimate what was environmentally available, correlate it with what was used at the site and thus observe processes of selectivity in past use of marine resources. Emphasis is given to the need to be untrame lled by present topography in understanding the palaeogeography of an area. Stress is laid on recognising that sea level change is not a single variable phenomenon in terms of its impact on people . INTRODUCTION For some time consequences of c hanges in sea level due to al t ernat ing periods of glaciation and deglaciation have been acknowledged by archaeologists. Three commonly prevailing attit udes are: a) Changes in sea level are seen to imply that, being near er or further away from the coast, one is more or less likely to explo i t fish and shellfish. b) The distance effect is assumed to remain reasonably throughout any geographical area.

uniform

c) The increased or decreased likelihood of exploiting marine resources is usually seen in the context of a single site and often for only a limited period of its occupation .

221

There are, however, other effects which are no less influential but which have not been so clearly perceived. By presenting a brief synthesis of some recent work on the palaeogeographic consequences of late Quaternary sea level changes, this pa'per attempts to s how some of these other areas which could have had a significant effect on entire regions, communities or individual sites. It is revealing to consider the problem on two different scales: firstly the macro-scale of the entire c ircum-Mediter r anean region, and subsequently on the micro-scale of a s pecific sit . ,Iin this case the example used is that of Franchthi Cave in the southern Argolid, Greece (23 0 8'E, 37 0 2S.S'N). Since much of the methodology has either already been published or else is in press (van Andel and Shackleton 1982, Shackleton, van Andel and Runnels 1984, van Andel and Lianos 1984), only a summary accounting of the palaeogeographi c reconstructions will be given here, mainl y in the figure capt i ons . Figures 1 and 2 show the circum-Mediterranean region at two different times, at 18,000 and 9,000 years before present (b.p. ) . MACROSCALE PALAEOGEOGRAPHIC RECONSTRUCTION It is my impression that, despite denials to the contrary, most of us still clothe the past topography with the shape of the present when we think about palaeogeography. For example, at low sea level the image of the present relief is merely extended the requi site extra kilometres seaward . Indeed, it is difficult not to do this. However, off almost all present coasts the continental shelf is essentially flat above 100 - 200m sea depth. Therefore at low sea level not only do most regions acquire additional land but more importantly this land is often of a different type from that found in the area today. The stippled area shown in Figure 1 makes this point. The plains which emerged in the Mediterranean region are of quite variable width, relatively narrow along much of the western part of North Africa, but very wide in the region of northern Tunisia and western Libya or the northern Adriatic. Quite clearly also, at the time of the height of the last glacial and at lowest sea level (-120m) (van Andel and Lianos 1984; Bloom 1977), the topographic consequences are felt unequally. The greater distance to the shore may have been of no more or even less importa nce to a region than the type of land exposed. In some cases large, flat plains emerged which do not exist at all in these regions today. Additiona lly, reconstructions of the palaeoshorelines f or the last glacial maximum (Figure 1 stands for the entire interval from about 28,000 15,000 yrs b.p.) obvi ously yield information a bout likely communication or migration route s. I shall not consider this more traditional aspect of palaeogeography in archaeology here; some further discussi on can be found in Cherry (1982) and Shackleton et al . (1984). Ins t ead, and more importantly, the effect of lowered sea level in terms of prehistoric exploitation patterns within any given region will be examined. Much recent archaeological research has concentrated on interpreting prehistoric act ivity in terms of the use of available r esources, 222

whether of food or of materials. For this line of enquiry one should obviously work from environmental reconstructions. Unfortunately, few studies have attempted to erect an adequate ba s e l ine in this way, even though lipservice may be paid to the fact tha t past environments may not have been like those observed at present (VitaFinzi and Higgs 1970 ) . It is for example quite possi bl e that in Epiros (Bailey, Carter, Gamble and Higgs 1983) a region of key importance for palaeolithic hunters may have been that of the coas tal plain which ran from present-day Corfu (or even the Gulf of Corinth) right to the head of the Adriatic. Bailey et a l . briefly mention an increase in area of available lowland grazi ng around Corfu. Given the glaciated mountains to the north and east, these plains should have been at least as well watered as the small Achilaos, Arta or Archarnaian plains are today. This extensive of plains region therefore might well have fed large herds herbivores, such as Equus hydruntinus. In which case the now submerged area could have assumed an importance in exploitation of resources beyond that of mere extension of existing type of ths of territory. Today only traces of the upland portion exploitation pattern remain to be examined. This example, besides showing a potential role of now wholly lost resource areas, also illustrates how far from the coastal zone the effects of sea level change may be felt. Figure 2 shows the circum-Mediterranean area at the end of the rapid part of the the post-glacial sea level rise. Discussion regarding the precise dating of the events of the rise continues, but there is wide agreement that it did not really start until about 14,000 years b.p., that it was indeed rapid, though there may have been fluctuations within the following interval of fast rising sea level, a nd that it slowed down considerably around 8,000 yrs b.p. (van Andel and Lianos 1984). It has been stated (Smith 1982:388) that, while c limate changes can occur very rapidly, the rise of the sea is so slow that communities, human or not, can easily adapt to the environmental changes that accompany the rise . It is not, however, the vertical movement of sea level that matters or that is observed, but the concomitant migration of the shore. The latter is a function of both the rate of rise and of the slope of the land. In this way shore migration can be swift and substantial, even if the rise of the sea is not particularly fast. In the northern Adriat ic, for example, the landward advance of the shore was, for a while, in the range of 3 - Skm per centur y, easily noticeable within a single human generation. During the rapid shore migrations, the actual shore environments tend to be transitory. The development of coastal features such as erosional cliffs, beaches, lagoons, muddy shoals, etc., takes time . This t i me is not available if the shore shifts rapidly away and the environments that were once shore become submerged. Thus coastal deposits tend to remain immature, consisting of thin, easily distu r bed sediments on the former land surface. Such ephemeral coasts provide more limited environmental opportunities for shellfish populations requi ring soft substra tes than do mature ones, and restrict the t i me available fo r their full development (Curray 1964). Furthermore, as the sea rose, the grazing lands of the coastal plains grew smaller and eventually 223

became segmented, forcing herbivore herds to retreat or to accept major shifts in their annual territories. Clearly changing sea level is not a simple variable that can be accounted for in the prehistoric scenery by taking the present topography and adding a seaward extension to fit whichever period is under investigation. MICROSCALE PALAEOGEOGRAPHIC RECONSTRUCTIONS The several effects of changing sea level discussed for the circumMedi terranean are an example on a macro-scale (of thousands of square kilometres) where broad reconstructions are sufficient for general purposes. This is not so when one looks at a small area, of a few tens of square kilometres or even less. At such a scale, it is only through detailed reconstruction of the palaeogeography that it becomes possible to monitor the changes in the resource base available to prehistoric inhabitants of a given area and so discern which resources could have been used . The second part of this paper illustrates this topic with a single site, Franchthi Cave in the southern Argolid (Figure 3), and its small area of surrounding coastline - its marine catchment. No very detailed interpretation of the occupation history of the site, from prior to about 28,000 yrs b.p. to the end of the main occupation some 5,000 years ago, has yet been published but Jacobsen (1976) provides a useful summary. This, and a detailed reconstruction of the palaeoshorelines and the changes in coastal environments which were the consequence of the rising sea level, form the foundation for the following discussion. Lest one think that the effect of the rising sea was simple, I should like briefly to repeat a point made in an earlier paper (van Andel and Shackleton 1980), to the effect that between 15,000 and 9,000 years ago the most productive area within a radius of 8km from the site, the lowlands, was reduced from more than 40% to less than 20% of the entire catchment (see Table 1, van Andel and Shackleton 1980). Nevertheless, it was during the later part of this major loss of territory that the use of the cave seems to have been intensified as shown by higher rates of deposition. In this ins tance at least, the correlation between a rising sea and the accompanying loss of resource and stresses on the people in the area is neither simple nor obvious. Accepting that the relation between shore migration and human history is not simple, the reconstruction of palaeoshorelines does allow one to achieve a more detailed understanding of at least one element of this history, that of the role of marine molluscs at the site during its long occupation (Shackleton in press). The main interest lies in the oppo rtunity to estimate what might have been available in the environment, correlate that with what was actually used, and through such a comparison observe processes of selection in past use of marine resources. A visitor to Franchthi today sees a large cave within a few tens of metres from the shore, at the tip of a headland on the north side of a shallow bay (Figure 3). During the last glacial maximum, the 224

entire Franchthi embayment, including the present bay, was land and the nearest shore lay some 7km to the west of the cave. Figure 4, condensed from a set of maps for many stages (Shackleton in press), illustrates the shore feature at lowest level and for two times during the subsequent rise. The maps have been compiled using high resolution seismic profiling combined with the application of general principles and analogies with the present shores of the Peloponnese (see van Andel and Lianos 1984). The late glacial coast consisted of salt marshes and lagoons behind sand barriers, and of extensive low, sedimentary cliffs probably with shingle beaches in front. During the following rise in sea level, illustrated by the map at 10,500 years b.p., the rapid migration of the shore left ephemeral beaches consisting mainly of mobile shingle or gravel with few molluscan resources. Such shellfish as was available would have been found on the rocky shores at the north side where the environment has remained roughly the same throughout the entire period of interest. By about 9,000 years b.p., the sea, beginning to rise more slowly, reached a more gently sloping shelf and a more complex series of shore features was formed. Salt marshes open on the seaward side appeared and a large inlet was formed which later became the present Koiladha Bay. Beaches and mudshoals completed the shore features of the central embayment, while rocky shores persisted in the north, and a complex of cliffs with shingle beaches in front occurred in the south. Clearly, as Figure 4 illustrates, palaeoreconstruction on a fine scale can furnish, in addition to the precise configuration of the coast at various times in the past, a reasonably detailed estimate of the types of shore environments that existed in the area, and consequently of the assemblages of marine molluscs which would have flourished in each. The first marine molluscs which represent food refuse appear in the cave about 10,500 years ago. This is not to suggest that prior to this date marine molluscs were not eaten by the users of Franchthi Cave. It is entirely possible that they were exploiting shellfish but were not returning the shells to the cave from the remote shore (see Meehan 1982, for a discussion of contemporary shellfish exploitation among the Anbara of northern Queensland, Australia ). The earliest evidence for eating shellfish at Franchthi, at about 10,500 b.p., consists of shells of Patella sp., Monodonta sp. and Gibbula sp. (Figure 5). The natural habitat of these species is a rocky shore such as exis ted, and still exists, along the northern shore of the embayment. It is interesting to note (Figure 4) that the beaches nearest to the cave, with their shingle deposits, did not provide suitable habitats for these rock-dwelling molluscs, and that the occupants of the site were bringing in shellfish from shores at a considerably greater distance from the cave. During the following few millennia, the rise of the sea began to slow and, with the exception of the rapid penetration of a large inlet which later would become the present Koiladha Bay, the distance from shore to Franchthi was not all that much smaller around 8,500 years ago than it had been at 10,500. The change in coastal environments, however, was dramatic. Around 9,500 b.p. an extensive area of shoals and open marshes, fronted at either end by sandy beaches, developed to both sides of the growing inlet. The 225

shores at 9,500 and 8,500 b.p. (the latter was chosen to illustrate these palaeoenvironments on Figure 4) would have provided a wide range of molluscs, particularly mud- and sand-dwelling bivalves, yet at both times the molluscan assemblage found in the cave is dominated by a single species, Cyclope neritea Linn' at 9,500 b.p., and Cerithium vulgatum Brugui're later. Both are common in the marsh and mudflat environment, c. neritea on open marshes and shallow muddy bottoms, while c. vulgatum adapts to both sandy and muddy bottoms in shallow water as well as harder substrates. It is not until some time after 7,800 b.p. that a mixed bivalve assemblage more truly representative of the shore environments since 9,500 b.p. appears in the cave deposits. DISCUSSION Elizabeth Voigt's work on material from the Middle Stone Age site of 0 0 Klasies River Mouth in South Africa (34 6'5, 24 24'E.) (1982) is an interesting and rewarding study of molluscs and shellfish gathering habits from a very long sequence (about 80 , 000 years). In this study, she demonstrates that differing areas of the beach were used for gathering and also shows which species of molluscs were favoured during the phases of occupation of the site. The variation in species present was seen as reflecting, "either variability or selective collecting relating to dietary preferences" (Voigt 1982:171). Her interpretation that this variation derives from selective gathering rests on her argument that, "Si nce the spec trum of species present in any one section of the sequence indicates that the full range of species was present, it is assumed that the variations reflect selec tive gathering." (Voigt 1982:171). In this instance, selectivity was deduced from using the variation in shells present in archaeological deposits. The advantage of using reconstructed palaeoshoreli~es to study selectivity in prehistoric shellfish gathering is that one is able to work from a broader base than the shell data from the site itself . While it is true that, in most instances, the only incontrovertible evidence for a species' eKistence in the past i s its presence in the archaeological record, it ~possible with such palaeoshor eline reconstructions to posit a list of molluscs likely to have been living in each of the environments shown for a given period. During the Cyclope neritea phase at Franchthi there was a largish area of very shallow water adjoining open saltmarsh in which today one usually finds such species as Cerastoderma glaucum Brugui're, and Bittium reticulatum Payraudeau, co-existing with c. neritea while bivalves such as Mactra corallina Linne and possibly Tapes decussatus Linn' and Venerupis aureus Gmelin occur at slightly greater depth on soft substrates. It is therefore possible that the presence of c. neritea in very large numbers and sometimes to the virtual exclusion of all other marine molluscs in the cave deposits represents selective gathering . It is clear also that, in environmental terms, the shores near Franchthi Cave have changed greatly with time, and that the present coast is not representative of all the configurations and environments of the past 30,000 years. Finally, it is evidence that exploitation of marine molluscs at 226

Franchthi was, at least in part, independent from the successive opportunities presented by the rising sea, and that, in part, the fluc tuating composition of shell f ish assemblages in Franchthi Cave is evidence of selective gathering. Climate change has so often been invoked as a deus ex machina to account for otherwise seemingly inexplicable changes in the prehistoric record, that I shall certainly not try to substitute sea level rise or fall as a more acceptable god to honour. Rather I wish to summarise by stating that sea level changes resulting from periods of glaciation and deglaciation produce profound and complex effects on the palaeogeography of large regions, and that on a local scale, their impact and complexity may be such that very detailed study of the coastal environmental history becomes indispensable as a component of archaeological studies of prehistoric resource use. With adequ,:i te reconstructions, on the other hand, the progress of sea level rise may be charted, for a given area, and its influence separated from other fac tors governing the practices and history of human coastal communities. ACKNOWLEDGEMENTS I should like to thank Margaret Oeith for her helpful comments on the manuscript and for the stimulating and encouraging discussions we have had . I am also very grateful to Tjeerd van Andel for both encouragement and the practical and generous help given in drafting the figures used in this paper.

REFERENCES Andel, T . H. van and Shackleton, J . C. (1980) Late Palaeolithic and Mesolithic coastlines of Greece and the Aegean, Journal of Field Archaeology 9, 445-454. Andel, T.H. van and Lianos, N. (1984) High resolution seismic r eflection profiles for the reco nstruction of post-glac ial transgressive shorelines: an example from Greece, Quaternary Research . 22, 31-45. Bailey, G., Carter , P ., Gamble , C. and Higgs, H. (1983) Epirus revisited: seasonali~y and inter-site variation in the Upper Palaeoli thic of north-west Gree ce. In Hunter-gatherer Economy in Prehistory, G. Bailey (ed) . Cambridge: Cambridge University Press. Bloom, A.L . (1977) Atlas of Sea Level Curves. International Geological Correlation Programme Project 61. Cornell University Press .

Ithica:

Cherry, J.F. (1981) Pat tern and process in the earliest colonisation

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of the Medite rr anean i slands , Prehistoric Society 47 , 41-68 .

Pr oceedings

of

the

Curray , J . R. (1964) Transgression and regression. In Papers in Marine Geology . Sheph erd Commemoration Volume , R. L. Miller (ed) , 175-203 . Jacobsen, T.W. (1976) 17,000 years of Greek prehistory, Scientific American 234 , 76-87 . Meehan, B. (1982) Shell Bed to Shell Midden. Canberra: Australian Institute of Aboriginal Studies . Shackleton, J.C., Andel, T. H. van and Runnels , C.N. (1984) Coastal Palaeogeography of the Central and Western Mediterranean during the last 125,000 years and its archaeological implications. Journal of Field Archaeology , 11, 307-314. Shackleton , J.C. (in press) Reconstructing past shorelines as an approach to determining factors affecting shellfish collecting in the prehistoric past. In Coastal Archaeology, G. Bailey and J. Parkington (eds). Cambridge: Cambridge University Press. Smith, P.E.L. (1982) The Late Palaeolithic and Epi-palaeolithic of northern Africa. In The Cambridge History of Africa Volume I: From the Earliest Times to about 500 BC. Ed. J.D. Clark. Cambridge: Cambridge University Press. Voigt, E.A. (1982) The mo1luscan fauna. In The Middle Stone Age at Klasies River Mouth in South Africa. Eds. R. Singer and J. Wymer. Chicago: Chicago University Press, 155-186.

In Fieller , N.R . J ., Gil bertson, D. D. and Ralph, N. G. A. 1985 Palaeoenvironmental Investigations: Research Design, Methods and Data Analysis. Symposium number 5(i) of the Association for Environmental Archaeology. Oxford: British Archaeological Reports International Series. 228

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