Science-Based Dating in Archaeology

295 Pages·1990·6.03 MB·English

by  M.J. Aitken

Longman Archaeology Series
Science-based dating in
archaeology
Longman Archaeology Series
Advisory editor:
Barry Cunliffe,
Professor of European Archaeology, University of Oxford
Each volume in this important new series will tackle a major theme
currently in need of synthesis or reassessment. The books are designed
for professional archaeologists, students and the serious amateur enthusiast,
and cover a range of levels as well as topics. A common feature of the
series is the application to archaeology of ideas and techniques derived
from anthropology, ethnology and other related disciplines.
*M. J. Aitken Science-based dating in archaeology
*Richard Bradley The social foundations of prehistoric Britain: themes and variations
in the archaeology of power
D. R. Brothwell Early British man: a bioarchaeology from the Palaeolithic to
the Middle Ages
R. W. Chapman Death, culture and society in prehistoric Europe: theory and applications
*Sean McGrail Ancient boats in N.W. Europe: the archaeology of water transport
to AD 1500
A. J. Parker Ships and shipping in the Mediterranean world: an archaeological
survey to AD 1500
*D. P. S. Peacock Pottery in the Roman world: an ethnoarchaeological approach
*D. P. S. Peacock & D. F. Williams Amphorae and the Roman economy: an
introductory guide
T. W. Potter Urbanisation in the classical world
*R. F. Tylecote The early history of metallurgy in Europe
* Already published
M. J. Aitken
Science-based
dating in
archaeology
O Routledge
Taylor Si Francis Group
LONDON AND NEW YORK
First published 1990 by Addison Wesley Longman Limited
Third impression 1997
Published 2013 by Routledge
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Copyright © 1990, Taylor & Francis.
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broaden our understanding, changes in research methods, professional practices, or medical treat­
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ISBN 13: 978-0-582-49309-4 (pbk)
British Library Cataloguing in Publication Data
Aitken, M. J. (Martin Jim)
Science-based dating in archaeology. - (Longman
archaeology series)
1. Archaeology Scientific techniques
I. Title
930'. 1028
Library of Congress Cataloging-in-Publication Data
Aitken, M. J. (Martin Jim)
Science-based dating in archaeology/M. J. Aitken.
- (Longman archaeology series)
Includes bibliographies and index.
ISBN 0-582-49309-9 ppr
ISBN 0-582-05498-2
1. Archaeological dating. I. Title. II. Series.
CC78.A39 1990
930.1'028'5-dcl9 89-2380
CIP
Contents
List of figures xiv
List of tables xvii
Preface xviii
Acknowledgements xx
1 Generalities 1
1.1 The impact of scientific techniques 1
1.2 Absolute dating and derivative dating 2
1.3 The event being dated 2
1.4 Reasons for dating 2
1.5 Which technique? 4
1.6 Dating terminology 4
Notes 5
2 Climatic clocks and frameworks 7
2.1 Introduction 7
2.2 Climate-based frameworks 7
Subdivisions: loess deposits 10
Late-glacial and Postglacial subdivisions 11
Global climate 11
2.3 The oxygen-isotope time-scale 12
2.3.1 Deep-sea cores 12
2.3.2 Isotopic fractionation 13
2.3.3 Records of isotopic variations 14
Correlation of continental climate 15
Labelling of stages and substages 17
Terminations 17
2.3.4 The Milankovitch astronomical theory of climate 17
Historical resume 17
Orbital parameters 19
Climatic response 19
vi Contents
2.3.5 Orbital tuning and chronostratigraphy 22
2.3.6 Ice-core variations 23
Relevance to radiocarbon calibration 24
Evidence of the Bronze Age eruption of Thera 25
2.4 The pollen record (palynology) 26
2.4.1 Aspects of pollen analysis 26
2.4.2 Pollen 27
Laboratory procedures; pollen diagrams 28
Quantity; preservation 29
2.4.3 Pollen zones and dating 29
Late-glacial and Postglacial dating in north-west Europe 29
Pollen assemblage zones (PAZ); chronozones 30
Correlation with the oxygen-isotope time-scale; La Grande
Pile; Les Echets 31
Phases of an interglacial 34
2.5 Varve chronology 35
The Scandinavian varve chronology 35
The Lake of Clouds, Minnesota 36
2.6 Dendrochronology (tree-ring dating) 36
2.6.1 Tree rings 37
Missing rings; false rings 38
Sapwood and heartwood 38
2.6.2 Sampling, measurement and data handling 39
Presentation of data 40
Cross-correlation 41
Replication and averaging 42
Signatures and signature years 43
2.6.3 Calibration of the radiocarbon time-scale 44
The bristlecone pine chronology 44
The European oak chronology 45
2.6.4 Dating of archaeological sites and structures 46
Sapwood estimates 47
2.6.5 Art-historical dating 47
Cross-dating 47
Notes 49
References 50
3 Radiocarbon - I 56
3.1 The essential basis 56
3.1.1 Radioactivity and occurrence; principle of dating 56
Time zero for timber 58
Exponential decay; lifetime 59
3.1.2 Historical 60
3.1.3 Measurement 61
Contents vii
3.2 The carbon exchange reservoir 61
3.2.1 The equilibrium concentration ratio 61
3.2.2 Iso topic fractionation 62
3.2.3 Mixing rates and residence times 64
The hard water effect 65
Volcanic emanation 65
3.3 Radiocarbon activity variations during past millennia 66
3.3.1 Known-age samples 66
3.3.2 Influence of geomagnetic field 68
Geomagnetic reversals 69
3.3.3 Sunspot activity: heliomagnetic modulation 69
3.3.4 Reservoir size and mixing rates 70
3.3.5 In situ production 70
3.4 Recent, man-made disturbances 71
3.4.1 The fossil-fuel effect (Suess effect) 71
3.4.2 Nuclear weapons testing 71
3.5 Other cosmogenic radioisotopes 72
Calcium-41 72
Notes 73
References 75
4 Radiocarbon - II 76
4.1 Measurement 76
4.1.1 The two approaches: beta activity and atom counting 76
4.1.2 Conventional beta counting 77
4.1.3 Statistical precision 78
The error multiplier 79
4.1.4 Isotopic enrichment; isotopic fractionation 82
4.1.5 Accelerator mass spectrometry (AMS) 82
Error limits; sample size 84
Impact on archaeology 85
4.1.6 Limits of meaningful age: terminology 85
4.2 Effect of contamination 85
4.3 Samples and sampling 86
4.3.1 Sample integrity; contamination 86
4.3.2 Sample types and laboratory pre-treatment 86
4.3.3 Collection 89
Sampling strategy 89
Archaeological association 90
Amount of sample 91
Documentation 92
Pre-cleaning 92
4.4 Steps towards a calendar date 92
4.4.1 The need for calibration 92
viii Contents
4.4.2 Conventional radiocarbon years 93
Years before present (BP) 93
Reference to modern standard 93
Isotopic fractionation 94
The age equation 94
Reservoir-corrected age 95
4.4.3 Combining dates 95
The expected spread 96
Weighted mean and its error limits 97
4.4.4 Calibration 98
Historical 99
High-precision calibrations 101
Probability spectra 103
Floating tree-ring sequences; ‘wiggle-matching’ 103
Coherence 105
4.5 Beyond calibration 108
Notes 108
References 114
5 Potassium-argon; uranium series; fission tracks 120
5.1 Potassium-argon dating 120
5.1.1 Basic principle 120
5.1.2 Measurement 120
The argon-argon technique 122
Laser dating of single grains 123
5.1.3 Age range; error limits 123
5.1.4 Archaeological application 123
5.2 Uranium-series dating 124
5.2.1 Basis 124
Thorium-230 124
Protactinium-231 126
5.2.2 Measurement 126
5.2.3 Age range; error limits 126
5.2.4 Sample integrity 127
Detrital contamination 127
‘Closed’ and ‘open’ systems 128
5.2.5 Archaeological application 128
Sample types 128
Speleothems and travertine 129
Bone and teeth 130
Coral and mollusc shells 131
5.2.6 Variants: ionium dating; uranium-234; lead-210 132
5.3 Fission-track dating 132
5.3.1 Basis 133
Contents ix
5.3.2 Measurement 133
Fading 134
5.3.3 Age range; error limits 134
5.3.4 Archaeological application 135
Provenance studies 136
5.3.5 Alpha-recoil tracks 136
Notes 136
References 137
6 Luminescence dating 141
6.1 Thermoluminescence (TL) 141
6.1.1 The phenomenon; the age equation 142
6.1.2 The mechanism responsible 143
The energy-level diagram 145
6.1.3 Measurement of TL 145
6.1.4 The plateau test 147
6.2 Palaeodose and annual dose 149
6.2.1 Palaeodose 149
6.2.2 Natural radioactivity: annual dose 150
A simple example 151
6.2.3 Moisture content 151
6.3 On-site procedures 153
6.3.1 Acceptability of contexts 153
6.3.2 Sampling requirements 155
6.3.3 Capsule burial 155
6.3.4 The portable gamma spectrometer 156
The gamma scintillometer 157
6.4 Laboratory measurements 157
6.4.1 Microdosimetry 157
6.4.2 The fine-grain technique 157
Palaeodose evaluation 158
6.4.3 Radioactivity measurements 158
Alpha counting 158
Beta TLD 159
6.4.4 Inclusion techniques (coarse-grain dating) 160
Quartz 160
Alkali feldspar; the isochron technique 162
Zircon dating; zoning and autoregeneration 163
6.5 Accuracy and error limits; date citation; age range 164
6.5.1 General 164
6.5.2 Random and systematic uncertainties 164
6.5.3 Date citation; publication 165
6.5.4 Age range 166