Practical and Theoretical Geoarchaeology E-Book

Paul Goldberg

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 881

Veröffentlichungsjahr: 2013

Beschreibung

Practical and Theoretical Geoarchaeology provides an invaluable overview of geoarchaeology and how it can be used effectively in the study of archaeological sites and contexts. Taking a pragmatic and functional approach, this book presents:

• 
  
• a fundamental, broad-based perspective of the essentials of modern geoarchaeology in order to demonstrate the breadth of the approaches and the depth of the problems that it can tackle.
  
• the rapid advances made in the area in recent years, but also gives the reader a firm grasp of conventional approaches.
  
• covers traditional topics with the emphasis on landscapes, as well as anthropogenic site formation processes and their investigation.
  
• provides guidelines for the presentation of field and laboratory methods and the reporting of geoarchaeological results.
  
• essential reading for archaeology undergraduate and graduate students, practicing archaeologists and geoscientists who need to understand and apply geoarchaeological methodologies.

Artwork from the book is available to instructors online at: www.blackwellpublishing.com/goldberg

“This is one of the best textbooks that I have read in years. I enjoyed reviewing it, and found it well-written and thorough in its coverage of the traditional earth science aspects of geoarchaeology. The non-traditional aspects were intriguing and equally thorough... I predict that this book will become the textbook of choice for geoarchaeology classes for several years.”

Geomorphology 101 (2008) 740–743

Leseprobe

Contents

Preface

Acknowledgments

Introduction

Part I Regional scale geoarchaeology

Chapter 1 Sediments

1.1 Introduction

1.2 Types of sediments

1.3 Conclusions: sediments versus soils

Chapter 2 Stratigraphy

2.1 Introduction

2.2 Stratigraphy and stratigraphic principles

2.3 Facies and microfacies

2.4 Correlation

2.5 Keeping track: the Harris Matrix

2.6 Conclusions

Chapter 3 Soils

3.1 Introduction

3.2 Soil profiles and soil properties

3.3 The five soil forming factors

3.4 Important soil forming processes

3.5 Conclusions

Chapter 4 Hydrological systems I: slopes and slope deposits

4.1 Introduction

4.2 Water movement on slopes

4.3 Erosion, movement, and deposition on slopes

4.4 Conclusions

Chapter 5 Hydrological systems II: rivers and lakes

5.1 Introduction

5.2 Stream erosion, transport, and deposition

5.3 Stream deposits and channel patterns

5.4 Floodplains

5.5 Stream terraces

5.6 Lakes

5.7 Conclusions

Chapter 6 Aeolian settings and geoarchaeological environments

6.1 Introduction

6.2 Sandy aeolian terrains

6.3 Examples of sites in dune contexts

6.4 Bioturbation in sandy terrains

6.5 Fine grained aeolian deposits

6.6 Conclusions

Chapter 7 Coasts

7.1 Introduction

7.2 Palaeo sea shores and palaeo coastal deposits

7.3 Conclusions

Chapter 8 Caves and rockshelters

8.1 Introduction

8.2 Formation of caves and rockshelters

8.3 Cave deposits and processes

8.4 Environmental reconstruction

8.5 Conclusions

Part II Nontraditional geoarchaeological approaches

Chapter 9 Human impact on landscape: forest clearance, soil modifications, and cultivation

9.1 Introduction

9.2 Forest clearance and soil changes (amelioration, deterioration, and disturbance)

9.3 Forest and woodland clearance features

9.4 Cultivation and manuring

9.5 Landscape effects

9.6 Conclusions

Chapter 10 Occupation deposits I: concepts and aspects of cultural deposits

10.1 Introduction

10.2 Concepts and aspects of occupation deposits

10.3 Stratigraphic sequences as material culture; concepts and uses of space

10.4 Time and scale

10.5 Settlement–landscape interrelationships

10.6 Origin and predepositional history of occupation deposits

10.7 Depositional history

10.8 Postdepositional modifications

10.9 Conclusions

Chapter 11 Occupation deposits II: examples from the Near East, North America, and Europe

11.1 Introduction

11.2 Tells

11.3 Mounds

11.4 Urban archaeology of Western Europe

11.5 Early medieval settlement

11.6 Medieval floors of Northwest Europe

11.7 Conclusions

Chapter 12 Experimental geoarchaeology

12.1 Introduction

12.2 Effects of burial and aging

12.3 Experimental “Ancient Farms” at Butser and Umeå

12.4 Conclusions

Chapter 13 Human materials

13.1 Introduction

13.2 Constructional materials

13.3 Metal working

13.4 Conclusions

Chapter 14 Applications of geoarchaeology to forensic science

14.1 Introduction

14.2 Soils and clandestine graves

14.3 Provenancing and obtaining geoarchaeological information from crime scenes

14.4 Other potential methods

14.5 Practical approaches to forensic soil sampling and potential for soil micromorphology

14.6 Conclusions

Part III Field and laboratory methods, data, and reporting

Chapter 15 Field-based methods

15.1 Introduction

15.2 Regional-scale methods

15.3 Shallow geophysical methods (resistivity, palaeomagnetism, seismology, ground penetrating radar)

15.4 Coring and trenching techniques

15.5 Describing sections: soils and sediments in the field

15.6 Collecting samples

15.7 Sample and data correlation

15.8 Conclusions

Chapter 16 Laboratory techniques

16.1 Introduction

16.2 Physical and chemical techniques

16.3 Microscopic methods and mineralogy

16.4 Thin section analysis

16.5 Minerals and heavy minerals

16.6 Scanning Electron Microscope (SEM), EDAX, and microprobe

16.7 Conclusions

Chapter 17 Reporting and publishing

17.1 Introduction

17.2 Management of sites and reporting

17.3 Fieldwork and assessment/evaluation reporting

17.4 Postexcavation reporting and publication

17.5 Site interpretation

17.6 Conclusions

Chapter 18 Concluding remarks and the geoarchaeological future

Appendices

Bibliography

Index

Dedicated by RIM to the late Peter Reynolds (Butser Ancient Farm, United Kingdom) and Roger Engelmark (University of Umeå, Sweden): pioneers of experimental farms (see Chapter 12)

From RIM: to Mum, Jill, and Flora

From PG: to my folks for sending me away to summer camp

© 2006 by Blackwell Science Ltd, a Blackwell Publishing company

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First published 2006 by Blackwell Science Ltd

1 2006

Library of Congress Cataloging-in-Publication Data

Goldberg, Paul.

Practical and theoretical geoarchaeology/Paul Goldberg and Richard I. Macphail.

p. cm.

Includes bibliographical references and index.

ISBN 0-632-06044-1 (pbk. : alk. paper) 1. Archaeological geology. I. Macphail, Richard. II. Title.

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                                                                                         2005018433

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Preface

Geoarchaeology within the past two decades has become a fundamental discipline whose value is recognized by everyone interested in past human history. First, archaeologists have become increasingly sensitive to the fact that sediments and stratigraphy provide the ultimate context for the artifacts and features that they excavate. Understanding this sedimentary context and its implications is a requisite for carrying out modern archaeology and for interpreting the archaeological record fully and accurately. Environmentalists (e.g. paleoecologists, soil scientists, sedimentologists, geologists, biologists, and climatologists) on the other hand, have turned to archaeology, because it provides a long-term view of human–environment interactions that have shaped both Quaternary and Holocene landscapes. Such knowledge can have a critical bearing on the future, for example, through identifying areas of sustainable landuse. Interpretation of such ecological information depends upon detailed understanding of the pedosedimentary and geomorphological context, as in archaeology. Geoarchaeology is an important discipline, because as shown recently, it increases our understanding of human impacts on the landscape through the study of ancient soils and occupation deposits. These investigations can provide detailed histories of human endeavors up to the present.

Although geoarchaeology – though not defined as such – had its roots at least in the eighteenth century (Rapp and Hill, 1998) it never came together as a subdiscipline until the appearance of the edited volume “Geoarchaeology: Earth Science and the Past” by Davidson and Shackley (1976). At this time Renfrew (1976) coined the term “geoarchaeology” in his Preface. Since then, a number of texts have appeared, the earliest ones (e.g. Rapp and Gifford, 1985) again were collections of papers, which were followed by single authored volumes (e.g. Waters, 1992; Rapp and Hill, 1998). In most cases however, the archaeological and human element as geoarchaeology was often underexplored in favor of landscape studies. This present volume, Practical and Theoretical Geoarchaeology, attempts to address this deficiency by providing what we feel is a more balanced view of the discipline by including detailed investigations of human activities as revealed by geoarchaeology. Potentially fruitful avenues of expansion of the discipline are highlighted, for example, in chapters on caves, experiments, occupation deposits, and forensic applications.

This book aims to be both an educational and practical tool, describing how geoarchaeology is carried out across a wide range of environments and periods, employing examples from many countries. It endeavors to teach readers both how to approach geoarchaeological problems theoretically and how to deal with them in practice. The topics covered range from regional-scale studies down to smaller, open area excavations and strata in past and present urban areas, such as Roman and Medieval London. The book presents numerous field and laboratory techniques, exposing readers to approaches suitable to a variety of site situations. Instructive guidelines and protocols are given to show the reader how to create integrated reports that include field evaluations, laboratory assessments, and archive and publication reports.

The book is designed primarily for undergraduate students in Archaeology and those Environmental and Geoscientists, who wish either to train in geoarchaeology or gain a background in this applied science. It is intended to serve as a basic text and an intermediary course in geoarchaeology. It also serves as a necessary text for advanced undergraduates and postgraduate students requiring access to geoarchaeological skills. In addition, it should act as a valuable resource for professionals in order to help develop their awareness of both field and laboratory methods and to identify the full potential of geoarchaeological investigations either for research or mitigation archaeology. Beginners in the subject may benefit from reading Chapters 1 to 3 first, which provide introductions to stratigraphy, sediments, and soils.

Acknowledgements

Those who know us are keenly aware how long it has taken us to get this book together. We thank them here at the outset for their patience and any grief we might have inflicted. There are too many people to thank individually, but a number of folks helped us considerably in writing the book.

Early discussions with Wendy Matthews were very stimulating and helped frame the focus of the book. Similarly, before we were too far along, David Sanger provided some fundamental insights about geoarchaeology and its practitioners. He reminded us that most geoarchaeology books are not written by archaeologists. Again, we hope that this helped us steer a more equitable course on the subject. Along the way we benefited from extensive and intensive collaboration and picked up valuable insights from Ofer Bar-Yosef, Steve Weiner, Takis Karkanas, Trina Arpin, Sarah Sherwood, Carolina Mallol, Arlene Rosen, Harold Dibble, Shannon McPherron, Steve Kuhn, Mary Stiner, Susan Mentzer, Lauren Sullivan, as well as Mike Allen, John Crowther, Gill Cruise, Johan Linderholm, the late Peter Reynolds, and Pat Wiltshire.

The staff at Blackwell has been exemplary, especially in light of the experiences that the authors have had with publishers. Delia Sandford and Rosie Hayden provided congenial help with a great deal of enthusiasm: a sheer pleasure. They also supplied a good deal of forgiveness and support along with Ian Francis, our editor. It was his questionable idea to contact us in the first place, and we are grateful for the opportunity to capitalize on it.

Students at Hebrew University, Boston University, the University of Tours, and the Institute of Archaeology, and members of the Archaeological Soil Micromorphology Working Group served as test subjects for various parts of this book over the years. Colleagues at HU (Na’ama Goren-Inbar, Nigel Goring-Morris, Anna Belfer-Cohen, and Erella Hovers) offered immense opportunities to observe exciting real-time geoarchaeology. Nigel Goring-Morris, simply one of the best field archaeologists around, furnished several examples of key sites that really helped build a geoarchaeological story. Colleagues at Texas (Mike Collins, Tom Hester, Britt Bousman, Lee Nordt, Charles Frederick) provided a different outlook and a growing experience, in spite of the accent. The years of field work at Dust Cave with Boyce Driskell revealed that anthropogenic deposits exist even for hunters and gatherers in the New World.

Over the years, the interaction with many geoarchaeologists similarly shaped our thinking. At the outset, the late Henri Laville served as an inspiration for cave sediments, along with Prof. F. Bordes. Marie-Agnès Courty has carried on this tradition of scholarship and friendship and has set the bar for geoarchaeological standards. Our first collaboration with her was invigorating and subsequent geoarchaeological interactions have helped us all develop and profit. We continue to be indebted to her.

Reid Ferring and PG were graduate students working in the Negev in the early 1970s and the latter has gained lots of insights into New World and Old World, geology, archaeology, and geoarchaeology, particularly in the field, waiting for things to happen. Rolfe Mandel and Vance Holliday, are among the foremost geoarchaeology practitioners, and they were instrumental in providing support, knowledge, and insights over the years. Much of this was sharpened by sharing the editorial helm with Rolfe at Geoarchaeology. Many hours were spent talking about the state of the discipline and the people who practice it. Vance Holliday in particular, devoted a lot of his time to furnish us with timely, constructive comments that significantly improved our message and how we should get it across. Not only are all these folks helpful, but they are simply nice people and made collaboration a pleasure. We also specifically would like to thank our other reviewer (from the United Kingdom), and Gill Cruise who played the devil’s advocate with parts of the text. Duncan FitzGerald provided valuable advice on several chapters.

Over the years, we have been encouraged by many other people and organizations who also supplied us with help, support, and information: Bud Albee, Nick Barton, Nick Bateman, Martin Bell, Francesco Berna, Sandra Bond, Mike Bridges, Barbara Brown, Brian Byrd, Dana Challinor, Nick Conard, Jane Corcoran, Andy Currant, John Darlymple, Roger Engelmark, John G. Evans, Nick Fedoroff, Charly French, Henri Galinié, Anne Gebhardt, Daffyd Griffiths, Ole Grøn, Simon Groom, Joachim Henning, John Hoffecker, Bruce Larson, Tom Levy, Elisabeth Lorans, Stephen Macphail, Curtis Marean, Roberto Maggi, Dominic Powlesland, Kevin Reeves, Mark Roberts, Thilo Rehren, Philippe Rentzell, Pete Rowsome, Tim Sara, Solveig Schiegl, Joe Schuldenrein, Astrid Schweizer, Christine Shaw, Jane Sidell, Michela Spataro, Julie Stein, Chris Stringer, Kathryn Stubbs, Ken Thomas, Peter Ucko, Brigitte Vliet-Lanöe, Steve Weiner, Alasdair Whittle, Tim Williams, Liz Wilson, Jamie Woodward, Elizabeth Zadora-Rio, the Universities of Frankfurt and Tours, the Institute of Archaeology (UCL), The Alexander von Humboldt Foundation, University of Tübingen, Albion Archaeology, Butser Ancient Farm, Corporation of London, English Heritage, Framework Archaeology, Museum of Londan Archaeology Service Norfolk Archaeological Unit, Suffolk Archaeological Unit, Oxford Archaeology, and Wessex Archaeology. We are grateful to all of you.

Introduction

Geoarchaeology has become highly prominent these days, and geoarchaeological themes appear in journal articles, monographs, and reports, either within a specific section of an article or as a stand-alone publication. Journals embrace not only mainstream “geoarchaeological” type of publications, such as Geoarchaeology or the Journal ofArchaeological Science, but also other journals that touch on more mainstream archaeological, anthropological, or geological subjects: Journal of Human Evolution, American Antiquity, Journal of Sedimentary Research, and Antiquity. In the United States, annual meetings of both the Geological Society of America (GSA) and the Society for American Archaeology (SAA), generally have at least one session or poster session, in addition to society-sponsored symposia on the subject. The GSA has an Archaeological Geology Division, and the SAA has the Geoarchaeology Interest Group. The Association of American Geographers (AAG) commonly has geoarchaeology sessions at their annual meetings.

Moreover, the most exciting archaeological sites that one reads about today – either in the popular press or professional literature – commonly have a substantial geoarchaeological component. The reader has only to be reminded about the significance of the geoarchaeological aspect of sites that are concerned with major issues relating to human development and culture. Some high profile issues and sites include: the use and evidence of the controlled use of fire (Zhoukoudian, China); the sedimentary context and the origin of early hominins (Dmanisi, Republic of Georgia; Boxgrove, United Kingdom; Mediterranean and South African caves – Gorham’s Cave, Gibraltar; Kebara Cave, Israel; Blombos Cave, South Africa); peopling of the New World (Meadowcroft Rockshelter United States; Monte Verde, Chile); Near Eastern urban cultures (Çatal Höyük, Turkey; Abu Salabikh and Tel Leilan, Syria), and early management of domestic animals (Arene Candide, Italy). Even previously excavated localities, such as the Folsom site, are being reinvestigated from a more sophisticated geoarchaeological perspective.

These well-known landmark sites have really drawn attention to the contribution that geoarchaeology can make to, and its necessity in, modern archaeological studies. This situation was not the case a few decades ago when only a handful of archaeological projects utilized the skills of the geoarchaeologist; one of the authors (PG) could enumerate the sparse number of geoarchaeological studies at the time he was a graduate student in the late 1960s. Still, the best results have come from highly focused geoarchaeological investigations that have employed the appropriate techniques, and that have been intimately linked to multidisciplinary studies that provide consensus interpretations.

This book is about how to approach geoarchaeology and use it effectively in the study of archaeological sites and contexts. We shall not enter into any detailed discussion of the origins and etymology of “Geoarchaeology” versus “Archaeological Geology.” (Full discussions of this irrelevant debate can be found in Butzer, 1982; Courty et al., 1989; Rapp, 1975; Rapp and Hill, 1998; Waters, 1992.) In a prescient, no-frills view of the subject Renfrew (1976: 2) summed it up concisely and provided these insights into the nature of geoarchaeology:

This discipline employs the skills of the geological scientist, using his concern for soils, sediments and land-forms to focus these upon the archaeological “site,” and to investigate the circumstances which governed its location, its formation as a deposit and its subsequent preservation and life history. This new discipline of geoarchaeology is primarily concerned with the context in which archaeological remains are found. And since archaeology, or at least prehistoric archaeology, recovers almost all its basic data by excavation, every archaeological problem starts as a problem in geoarchaeology.

These issues of context, and what today would be called “Site Formation Processes” in its broadest sense, can and should be integrated regionally to assess concerns of site locations and distributions, and geomorphic filters that might have controlled them.

In this book – as will be seen throughout the volume – we take a decidedly pragmatic and functional approach. We do not see any need to differentiate between the two and consider geoarchaeology, archaeological geology, and geological archaeology to fall under the same rubric: any issue or subject that straddles the interface between archaeology and the earth sciences. Classifications – and in this case the distinctions between geoarchaeology and archaeological geology – are of value only if they are ultimately useful. Does it really matter how we categorize research that is aimed at studying postdepositional dissolution of bones at a site? According to the above this research would fall into both camps, but does it help us to know if we are doing geoarchaeology or geological archaeology or archaeological geology? For the sake of brevity, we employ the simple term, Geoarchaeology.

Geoarchaeology is practiced at different scales (Stein and Linse, 1993). Furthermore, its use and practice vary according to the training of the people involved and the goal of their study. For example, geologists and geographers may well emphasize the mapping of large-scale geological and geomorphological features – such as where a site may be situated within a drainage system – or other regional landscape features. This is a regional perspective scale that exists in three dimensions, with relative relief possibly being measured in thousands of meters, especially if working in the Alps and Andes. Much of the geoarchaeological research carried out in North America is focused at this landscape scale. Geologists would also be interested in the overall stratigraphy of site deposits and how these might interrelate to major landforms, such as stream terraces, glacial landforms, and loess plateaus. Pedologists, on the other hand, would be more concentrated on the parent materials, the surfaces upon which soils were formed, and how both have evolved in conjunction with the landscape; such materials can be buried by subsequent deposition or can be found on the present-day surface. In either case, pedologists’ focus tends to be on the scale of the soil pit, that is, on the order of meters. Archaeologists themselves may want to focus geoarchaeological attention upon microscale, centimeter-thick occupation deposits: what they are, and how they reflect specific or generalized past human activities. In the case of rescue/mitigation archaeology – commonly termed Cultural Resource Management (CRM) in the United States – geoarchaeology is tailored to the nature of the “job specifications” proscribed by the developer under the guidelines of salvage operations. Finally, the geoarchaeologist may well be just one member of an environmental team whose task is to reconstruct the full biotic/geomorphic/pedologic character of a site and its setting, and how these environments interacted with past human occupations. All these approaches can be relevant depending on the research questions involved, and holistically they could be subsumed under the term, “site formation processes” (Schiffer, 1987).

Archaeologists come from a variety of backgrounds. As stated above, in North America, archaeology is taught predominantly in anthropology programs, although some universities (e.g. Boston University, United States, and Simon Fraser University in Canada) actually have archaeology departments; Classical and Near Eastern Archaeology programs are not rare, and these tend to emphasize written sources over excavation. In Europe, archaeology is included within programs, or in departments and institutes, and not necessarily as an extension of anthropology.

Although in the United Kingdom, geoarchaeology is taught in a number of archaeological departments, this is not always the case in Europe as a whole. In France, for example, this subject may only be taught to prehistorians and not to classical or medieval archaeologists. Commonly, even in the United Kingdom and elsewhere in the world, geoarchaeology is more likely to be seen as an ad hoc offshoot of geology and geography. In North America, it is not anchored in any particular department and may be cross-listed among Anthropology, Archaeology, Geology, and Geography. In spite of good intentions and good training, many geoscientists tend to be naïve in their approach to solving archaeological problems, and as a consequence they effectively reduce their potential in advancing this application of their science. This often diminishes or even negates their contributions to interdisciplinary projects. The opposite situation can be found, where an archaeologist does not even know what questions to ask (Goldberg, 1988; Thorson, 1990).

Thus, as Renfrew (1976) so cogently demonstrated, geoarchaeology provides the ultimate context for all aspects of archaeology from understanding the position of a site in a landscape setting to a comprehension of the context of individual finds and features. Without such knowledge, even the most sophisticated isotope study has limited meaning and interpretability. As banal as it might sound, the adage, “garbage-in, garbage-out” is wholly pertinent if the geoarchaeological aspects of a site are ignored.

In the past, geoarchaeology was carried out very much by individual innovators. In North America, the names Claude Albritton Jr., Kirk Bryan, E. Antevs, E.H. Sellards, and C. Vance Haynes immediately come to mind as the early and prominent leaders in incorporating the geosciences into the framework of archaeology (see Holliday, 1997 and Mandel, 2000a for details). In fact, Mandel aptly points out that for the Great Plains, geoarchaeology – or at least geological collaboration – locally constituted an active part of archaeological survey for several areas, although it was patchy in space and time. Much of the emphasis was focused on evaluating the context of Paleoindian sites and how these occurrences figured into the peopling of the New World (Mandel, 2000).

In Europe, during the period from the 1930s to the 1950s, Zeuner (1946, 1953, 1959) at the Institute of Archaeology (now part of University College London), developed worldwide expertise in the study of the geological settings of numerous Quaternary and Holocene sites that ranged from India to Gibraltar. After Kubiëna (1938, 1953, 1970) called the world’s attention to soil micromorphology, Cornwall (1958) also at the Institute of Archaeology, applied this technique to archaeology for the first time (see below). At the same time, Dimbleby (1962) developed the link between archaeology and environmental studies, and produced one of the first detailed investigations of past vegetation and monument-buried soils for Bronze Age England Dimbleby (1962). Duchaufour (1982) in France also systematically studied environmental change and pedogenesis. In mainland Europe, the legendary French prehistorian François Bordes (1954) – whose doctorate in geology dealt with the study of loess, paleosols, and archaeological sites, principally in Northern France – placed the French Palaeolithic within its geomorphologic setting. Vita-Finzi (1969), working in the Mediterranean Basin, used archaeological sites to suggest the chronology of Mediterranean valley fills, which he related to both climatic and anthropogenic factors. Cremaschi (1987) investigated paleosols and prehistoric archaeology in Italy.

Although some geoarchaeological research is funded by granting agencies (NSF, NGS, NERC, CNRS), much, if not most, of modern geoarchaeological work – in both the New and Old Worlds – is fostered and sponsored by CRM projects, ultimately related to human development throughout the world. Approaches and job specifications vary according to whether investigations are at one end of the spectrum, short-term one-off studies, or long-term research projects at the other. Geoarchaeological work can be done by single private contractors or by huge international teams, which may well include specialists who also act as private contractors. Nowadays, local authorities, government agencies (e.g. State Departments of Transportation in the United States) and national research funding agencies (e.g. NSF in the United States, AHRB and English Heritage in the United Kingdom, AFAN and the CNRS in France, and Nara National Institute in Japan) may all be involved in commissioning geoarchaeological investigations. It is currently a very flexible field. It is also one where there is an increasing need for formal training, but where relatively few practitioners have been in receipt of one.

Geoarchaeological work is now often broken up into several phases, with desktop investigations, fieldwork survey, excavation, sample assessment, and laboratory study, all being likely precursors to full analysis and final publication. This is all part of modern funding and operational procedures.

Single-job or site-specific studies may be as straightforward as finding out “What is this fill?” whereas problem-based research could involve the gathering of geoarchaeological data on the possible first controlled use of fire, as at Zhoukoudian, China (Goldberg et al., 2001; Weiner, 1998). Sites are investigated at different scales and sometimes, for very different reasons. At one time “dark earth” – the dark colored Roman-medieval urban deposits found in urban sites across northern Europe – engaged the particular interest of geoarchaeologists because these enigmatic deposits commonly span the “Dark Ages,” and human activities at this time were poorly understood (Macphail, 1994; Macphail et al., 2003). Analysis of “dark earth” therefore, became a research-funded topic for urban development sites (CRM projects in urban areas) across Belgium, France, and the United Kingdom, for example. On the other hand, attention can be focused on individual middens and midden formation because they provide a wealth of material remains, particularly organic, that are normally poorly preserved and complex to understand and interpret (Stein, 1992). Regional studies of the intertidal zone, for example, may include the investigation of middens as one single component. The recent study of the intertidal deposits of the River Severn around Goldcliff, Wales, for example, involved analysis of sediment and drowned soils in order to investigate sea level changes and their effects on the populations living in the coastal zone during the Mesolithic through Iron Age periods (Bell et al., 2000). Equally, studies of alluvial deposits and associated flood-plains (Brown, 1997; French, 2003) have involved the search for buried sites, within the overall realm of evaluating the distribution of archaeological sites. The Po plain of Italy (Cremaschi, 1987) and the Yellow River of China (Jing et al., 1995) both feature a series of late prehistoric settlements. Many of the most significant Paleoindian and Archaic sites in the United States are situated within alluvial sequences (Ferring, 1992, 1995; Mandel, 1995, 2000a).

Modern geoarchaeological research makes use of a vast number of techniques that either have been used in geology and pedology or have been developed or refined for geoarchaeological purposes. Early geoarchaeological research until the latter part of the last century, at least in North America, was predominantly field-based and made use of both natural exposures and excavated areas. More recently, field techniques have become more improved and technologically sophisticated (Hester et al., 1997). Natural exposures can be supplemented with surface satellite remote sensing data (Scollar, 1990), as well as subsurface data derived from machine-cut backhoe trenches, augering, coring, and advanced geophysical techniques (e.g. magnetometry, electrical resistivity, and ground penetrating radar-Kvamme, 2001). Moreover, such data can be assembled and interrogated using Geographic Information Systems (GIS; Wheatley and Gillings, 2002) that can be used to generate and test hypotheses.

Laboratory techniques have similarly become more varied and sophisticated. At the outset, many geoarchaeological studies adopted techniques from geology and pedology that were aimed at sediment/soil characterization. Thus traditional techniques characteristically consisted of grain-size analysis (granulometry), coupled with other physical attributes (e.g. particle shape, bulk density, bulk mineralogy), as well as basic chemical analyses of organic matter, calcium carbonate content, extractable iron, and so on. The analysis of phosphate to elucidate activity areas or demarcate site limits has a longer history spanning over 70 years (Arrhenius, 1931, 1934; Parnell et al., 2001). Conventional techniques with long historical pedigrees, such as x-ray diffraction (XRD), electron microprobe, x-ray fluorescence (XRF), instrumental neutron activation analysis (INAA), and atomic absorption (AA) have been enhanced by rapid chemical, elemental, and mineralogical analyses of samples through the use of Fourier transform infrared spectrometry (FTIR), Raman spectrometry, and inductively coupled plasma atomic emission spectrometry (ICP-AES) (Pollard and Heron, 1996).

In addition, a notable advance in geoarchaeology has been the application of soil micromorphology to illuminate a wide variety of geoarchaeological issues (Courty et al., 1989; French, 2003). These issues range from the development of soil and landscape use (e.g. Ayala and French, 2005; French and Whitelaw, 1999; Romans and Robertson, 1983) and the formation of anthropogenic deposits (Macphail et al., 1994; Matthews, 1995; Matthews et al., 1997) to the evaluation of the first uses of fire (Goldberg et al., 2001).

Finally, geoarchaeological research has been facilitated by the development of numerous dating techniques just within the past two to three decades. Now, sites within the span beyond the widely accessible limits of radiocarbon are potentially datable with techniques, such as thermoluminescence (TL), optically stimulated luminescence (OSL), and electron spin resonance (ESR) (Rink, 2001).

In this book, we aim to present a fundamental, broad-based perspective of the essentials of modern geoarchaeology in order to demonstrate the breadth of the approaches and the depth of problems that can be tackled. As such, it is also aimed to promote a basic line of communication and understanding among all multidisciplinarians. We cover a variety of topics that discuss thematic issues, as well as practical skills. The former encompasses such broad concepts as stratigraphy, Quaternary and environmental studies, sediments, and soils. We then provide a survey of some of the most common geological terrains that provide the natural settings for almost all archaeological sites. These are established geoarchaeological topics into which we have incorporated some new findings. Unlike previous books on geoarchaeology, we have dedicated a second major portion of the volume to new topics that are normally not entertained by previous geoarchaeological texts, such as “human impact,” “experiments,” and occupation deposits including Roman and medieval archaeology, and forensic applications. It is important also to obtain some insights into practical aspects of geoarchaeology, including how specifically geoarchaeologists should fit in to a project. Similarly, two chapters are devoted to a presentation of the methods – pragmatic and theoretical – currently used in geoarchaeology. These include not only field techniques (e.g. the use of aerial photos, how to describe a profile, and collect samples), but also those techniques that are used in the laboratory. Although we summarize the “what,” and “how,” we also try to emphasize the “why,” and provide a number of example-based caveats for important techniques. A final facet deals with the practical aspects of reporting geoarchaeological results, keeping in mind that material presented in reports differs from that in articles. Reports essentially present the full database and arguments, whereas articles are commonly more thematic and focused, and by necessity are constrained to present results more concisely. Reports, which are seldom published in full, constitute the “gray literature” and make up an important part of the scientific database. They are too commonly overlooked, ignored, or simply are not readily accessible.

As a final point, we maintain that geoarchaeology in its broadest sense, must be made understandable to all players involved, be they archaeologists with strong training in anthropology, or the geophysicist, with minimal exposure to archaeological issues. All participants should have enough of a background to understand what each participant is doing, why they are doing it, and most importantly, what the implications of the geoarchaeological results are for all team members. Too often we hear about the geospecialist simply turning over results to the archaeologist, essentially being unaware of the archaeological problem(s), both during the planning stages and later during execution of the project. Hence they cannot correctly put their results to use. On the other hand, many archaeologists tacitly accept results produced by specialists with few notions on how to evaluate them. This book attempts to level the playing field by providing a cross-disciplinary background to both ends of the spectrum. Such basic material is needed to establish a dialogue among the participants so that problems can be mutually defined and mutually understood, regardless of whether you call yourself an archaeological geologist or geoarchaeologist.

Part I

Regional scale geoarchaeology

Introduction to Part I

Geoarchaeological endeavors operate at a variety of scales. These undertakings range from regional views of archaeological sites – their distributions and associated activities (e.g. cultivation, hunting ranges, trading routes, and networks) – to microscopic study of the deposits, artifacts, and features found within them. In the following chapters we examine the issues linked to landscape scale geoarchaeology, and describe the most salient aspects of some of the principal geological environments and processes that geoarchaeologists are likely to encounter. Although archaeological sites and associated remains can be found in most geological environments (including what is now marine; Faught and Donoghue, 1997), most human occupations, or at least their traces, are not evenly spread throughout these environments. Sites associated with temperate fluvial (stream) environments, for example, are considerably more abundant than those from desertic or glacial terrains. Thus, although we try to touch on all these situations, we may provide more detail for those with greater representation in the geoarchaeological record. Detailed treatises on geological environments can be found in many geomorphology and sedimentology texts, such as Boggs, 2001; Easterbrook, 1993; Reading, 1996; and Ritter et al., 2002.

1

Sediments

1.1 Introduction

Sediments – those materials deposited at the earth’s surface under low temperatures and pressures (Pettijohn, 1975) – constitute the backbone of geoarchaeology. The overwhelming majority of archaeological sites is found in sedimentary contexts, and the material that is excavated – whether geogenic or anthropogenic – is sedimentary in character. In this section we examine some of the basic characteristics of sediments, many of which can also be applied to soils (Chapter 3). We have two principal goals in mind. Since sediments are so ubiquitous in archaeological sites, it is necessary to have at least a working knowledge of some of these characteristics so as to be able to share this descriptive information with others. Essentially, these descriptive characteristics constitute a lingua franca: the term “sand” (Table 1.1), for example, corresponds to a defined range of sizes of grains, irrespective of composition. Second, and perhaps more important, is that many of the descriptive parameters that we observe in sediments commonly reflect – either individually or collectively – the history of the deposit, including its (1) origin, (2) transport, and (3) the nature of the locale where it was deposited, that is, its environment of deposition. Figuring out these three aspects of a sediment’s history constitutes a subliminal mindset of sedimentologists, whether they are studying a 100 m thick sequence of Carboniferous sandstones in Pennsylvania or a 10 cm thick sandy layer within a Late Pleistocene cave in the Mediterranean. In sum, by observing and recording the lithological attributes of a sediment we not only provide an objective set of criteria to describe it, but also a means to get some insights into its history.

1.2 Types of sediments

Sediments can be classified into three basic types, clastic, chemical, and organic, of which the first two are generally the most pertinent to geoarchaeology. Clastic sediments are the most abundant type. They are composed of fragments of rock, other sediment, or soil material that reflect a history of erosion, transport, and deposition. Most clastic sediments are terrigenous and deposited by agents such as wind (e.g. sand dunes), running water (e.g. streams, beaches), and gravity (e.g. landslides, slumps, colluvium). Typical examples of clastic sediment (as based on decreasing sizes of the components) are sand, silt, and clay (Table 1.1). In the geological record, when such materials become lithified, the resulting rock types are sandstone, siltstone, and shale, respectively.

Volcaniclastic debris, consisting of volcanic ash, blocks, bombs, and pyroclastic flow debris are also considered as clastic sediments (Fisher and Schmincke, 1984), Overall, they are relatively uncommon in geoarchaeological contexts as they are restricted to volcanic areas. Nevertheless, they constitute an important aspect in the stratigraphy and formation of some key archaeological sites. Pompeii, considered the type site for depicting instances in archaeological time (Binford, 1981), is covered by about 4 m of volcaniclastic debris (tephra), consisting of pumice, volcanic sand, lapilli (2–64 mm), and ash (<2 mm) (Giuntoli, 1994). The site of Ceren, in San Salvador, represents a similar type of setting, where structures and agricultural fields were buried under several meters of tephra (Conyers, 1995; Sheets, 1992). Volcaniclastic deposits in rift valleys play critical roles in the dating and stratigraphy of Pliocene and Pleistocene deposits from sites in East Africa, the Jordan Rift, Turkey, and Georgia. Sites such as Olduvai Gorge, Koobi Fora, Gesher Benot Ya’akov, and Dmanisi, are just a few of the sites where archaeological and hominin remains are intercalated with volcanic rocks and tephra (Ashley and Driese, 2000; Deocampo et al., 2002; Gabunia et al., 2000; Goren-Inbar et al., 2000; Stern et al., 2002).

TABLE 1.1 Common grain size scales used in geology and pedology

Marine organisms such as mollusks and corals, for example, produce shells of calcium carbonate. In cases where these hard body parts are subjected to wave action, they can be broken into small centimeter to millimeter size fragments, resulting in the formation of a bioclastic limestone, for example (Table 1.2). Coquina is an example of a coarse bioclastic sediment, whereas chalk is composed of silt and fine sand-size tests of marine organisms (foraminifera); in other cases organisms may have siliceous skeletons as is the case with diatoms, resulting in the formation of diatomite. Biological remains, such as ostracods, diatoms, and foraminifera, can be preserved within otherwise mostly mineralogenic deposits. The moat deposits from the Tower of London, for example, contained numerous diatoms that suggested shallow, turbid water in disturbed sediments (Keevill, 2004). These conditions were inferred to be a result of inputs into the moat of waste disposal, surface water, and water from the Thames and the City Ditch.

TABLE 1.2 Types of sediments; consolidated (lithified), rock equivalents for clastic sediments are given in parenthesis. Note that bioclastic limestones, composed of biologically precipitated shell fragments (e.g. coquina), can be thought to be both clastic and biochemical in origin

Chemical sediments are those produced by direct precipitation from solution. Lakes in semiarid areas with strong evaporation, for example, will exhibit a number of precipitated minerals, such as halite (table salt), gypsum (calcium sulphate), or calcite or aragonite (both forms of calcium carbonate). In cave environments, chemical sediments are widespread and typically produce sheets of calcium carbonate (e.g. travertine or flowstone), or ornaments such as stalactites and stalagmites. These are usually composed of calcite or aragonite, but other peculiar minerals can be composed of phosphates, nitrates, or sulphates (Hill and Forti, 1997). The third group, biological sediments, is composed mostly of organic materials, typically plant matter. Peats or organic-rich clays in swampy areas and depressions are characteristic examples.

1.2.1 Descriptive and interpretative characteristics of sediments

1.2.1.1 Clastic sediments

Clastic sediments display a number of properties that can be described and ultimately interpreted. These characteristics include composition, texture (grain size and shape), fabric, and sedimentary structures.

Composition. Sediments can exhibit a wide variety of composition of mineral and rock types, and normally this is a function of the source of the material (Tables 1.3 and 1.4). For this reason, geologists are able to reconstruct geological landscapes (e.g. former landmasses in Table 1.4) that have long since been eroded. In spite of their wide variety, certain rocks and minerals occur repeatedly in sediments (“major minerals” in Table 1.3). Their relative abundance in a sediment can vary with location and age. In the case of the latter, some minerals (e.g. olivine) are more susceptible to alteration/destruction than others, and thus they can be less persistent in older sediments. Furthermore, overall sediment composition can be influenced by secondary processes (e.g. weathering, soil formation, diagenesis) that result in the precipitation of minerals that either cement the skeletal grains of the sediment, or that precipitate as concentrations within the sedimentary mass (e.g. nodules and concretions). Secondary mineralization may involve carbonates (e.g. calcite, aragonite), silicates (e.g. opal, microcrystalline quartz/chert), sulfates (e.g. gypsum, barite), and iron oxides (e.g. limonite, goethite).

TABLE 1.3 Common minerals and rock fragments in sediments (modified from Boggs, 2001)

Major minerals

• Quartz

• Potassium and plagioclase feldspars

• Clay minerals

Accessory minerals

Micas: muscovite and biotite

Heavy minerals (those with specific gravity >2.9):

• Zircon, tourmaline, rutile

• Amphiboles, pyroxenes, chlorite, garnet, epidote,

olivine

• Iron oxides: Hematite, limonite, magnetite

Rock fragments

• Igneous

• Metamorphic

• Sedimentary

TABLE 1.4 Heavy mineral associations and related geological sources (modified from Pettijohn et al., 1973)

Mineral association

Typical geological source

Apatite, biotite, brookite, hornblende, monazite, muscovite, rutile, titanite, tourmaline, zircon

Acid igneous rocks

Augite, chromite, diopside, hypersthene, ilmenite, magnetite, olivine

Basic igneous rocks

Andalusite, corundum, garnet, phlogopite, staurolite, topaz, vesuvianite, wollastonite, zoisite

Contact metamorphic rocks

Andalusite, chloritioid, epidote, garnet, glaucophane, kyanite, sillimanite, staurolite, titanite, zoisite-clinozoisite

Dynamothermal metamorphic rocks

Barite, iron ores, leucoxene, rutile, tourmaline (rounded grains), garnet, illmanite, magnetite, zircon (rounded grains)

Reworked sediments

FIGURE 1.1 Triangular grain size diagrams with sand, silt, and clay end-members. (a) These diagrams illustrate the large differences and variability in class names and boundaries as used by American geologists. (b) A similar type of triangular diagram as employed by American and British soil scientists. Note the widespread occurrence of the term “loam” and its variants (e.g. sandy loam) to describe soil textures. Furthermore, compare the size of the “Clay” field in this soil diagram with that of “Clay” as used by geologists in (a) (1.1a, modified from Pettijohn, 1975).

Although the methods for grain size analysis are discussed in Chapter 16, we point out here that sediments are commonly mixtures of different sizes of particles. The proportions of sand–silt–clay, for example, in sediments and soils are commonly presented in terms of three major end-members, as shown in the triangular diagrams of Figure 1.1. Not surprisingly, different mixtures of these end-members have different names, such as “sandy clay” or “silty sand” that vary from author to author, and from discipline to discipline (again, geology versus pedology – cf. Figs 1.1a versus 1.1b). Figure 1.1a, for example, shows four triangular diagrams with different limits between different classes. In addition, soil scientists use the additional term loam, which is defined by the USDA to be composed of 7–27% clay, 28–50% silt, and <52% sand; many soils fall into the “loamy” category, being sandy, silty, or clayey loams (Soil Survey Staff, 1999). A silty loam equivalent for a geological deposit could fall into the “silty sand” or “silty clayey sand” category depending upon which sedimentary classification scheme is used. The point is that, again, one has to be aware of the background of the author of the grain size analysis: whether the classification system used is geological or pedological and from which country they are from, since class limits vary from country to country. Thus, the term loam, should more properly be used to describe soils and not sediments.

Sorting is a term applied to the proportion and number of different size classes comprising the grain populations. In particular, it relates to the statistical distribution of sizes around the mean (the standard deviation; see Tucker, 1988 for ways to measure and evaluate it). Sorting can be readily visualized in Figure 1.2. The predominance of one particle size indicates a well-sorted sediment. Beach and dune sands, for example, are characteristically well sorted, as are windblown dust deposits, known as loess. A poorly sorted sediment consists of numerous amounts of different particle sizes. Slope deposits, where a mass of sediment has been moved downhill (the process of colluviation) and glacial till are typically poorly sorted deposits.

FIGURE 1.2 Illustration of the concept of sorting. (a) well-sorted sand; (b) well-sorted silt; (c) bimodal: well-sorted silt and sand; (d) well-sorted sand of varying composition; (e) moderately sorted sand; (f) poorly sorted silt; (g) bimodal: poorly sorted sand in a well-sorted silt; (h) unsorted (modified from Courty et al., 1989).

Particle shape is usually considered for pebbles and sand-size grains. It is another descriptive parameter and an indicator of grain and sediment history. Three related features of shape are generally considered. Form refers to the general outline of the grain and ranges from equant grains (with roughly equal length, width, and thickness dimensions approaching the shape of a sphere), to platy or disc-shaped grains, in which the thickness is markedly less than the length or width (see Boggs, 2001; Mueller, 1967 for methodological details to measure shape). Roundness, on the other hand, relates to the angularity of a grain and is concerned with the jaggedness of the edges (Figs 1.3a,b). Finally, surface texture refers to the microtopographic features of the grain, such as pitting, etch marks, and micro fractures; grains may vary from pitted to smooth.

The importance of form is not universally agreed upon, and its measurement should be viewed in light of other sedimentary parameters (Boggs, 2001). Form is more pertinent to the coarser, pebble fraction, as the finer sand fraction (generally quartz) seems to be only slightly modified if at all by transport. The most noteworthy example comes from beach pebbles and cobbles, which tend to be flattened, although the reasons for this are not clear. In fluvial environments, shapes can be associated with ease of transport, so that spherical and prolate shapes tend to be more readily transportable than are blady particles.

Grain roundness is a function of mineralogy, size, transport, and distance of transport (Boggs, 2001). For sand-size quartz grains, for example, increased roundness is commonly associated with aeolian transport, which is more effective in rounding grains than is water. For larger pebbles, composition plays an increasingly important role. Limestone pebbles, for example, are much easier to round in fluvial environments than are those from cherts, which tend to fracture before they become rounded. On the other hand, the presence of well-rounded chert pebbles is commonly indicative of several cycles of reworking and points to relatively greater age than fresh angular chunks. In any case, well-rounded pebbles point to fluvial transport, where rounding tends to take place relatively rapidly after a clast enters the fluvial system.

FIGURE 1.3 Aspects of particle shape. (a) Depicts the form of grains as expressed as the ratio of long (I), intermediate (i), and short (s) axes of the grain. (b) Two aspects of shape are illustrated here, roundness and sphericity. The columns depict changes from well-rounded to angular grains. The rows illustrate grains of different sphericity classes: the grains in the upper row are more equi-dimensional than the elongated grains in the lower row (modified from Courty et al., 1989). (c) Photograph of Layer I26 from the Lower Palaeolithic site of ‘Ubeidiya, Jordan Valley, Israel. The flat, “pavement-like” disposition of the one-pebble-thick layers was suggestive of anthropogenic origin, but unfortunately shape analysis of these clasts by Bowman and Giladi (1979) could not resolve this issue.

Shape analysis was applied to the study of pebbles and cobbles from Layer I26 at the Lower Palaeolithic site of ‘Ubeidiya in the Jordan Valley (Fig. 1.3c) (Bar-Yosef and Tchernov, 1972; Bar-Yosef and Goren-Inbar, 1993). Here, it was not clear whether a pebble “pavement” represented the substrate of living floors or natural accumulations. Unfortunately, morphometric analysis (size, roundness, shape, and sphericity) and comparison to modern beach pebbles from the Sea of Galilee (Bowman and Giladi, 1979) revealed ambiguous results, and it was not possible to differentiate whether these gravels were of fluvial, beach, or human origin. The uniform thinness of the gravel layer and lack of imbrication, however, was suggestive of anthropogenic influence.

Studies of surface texture usually involve sand-size particles. Signs of fracture and abrasion produced during transport, as well as diagenetic changes expressed as etching and secondary precipitation can be observed under the optical (binocular and petrographic) and electronic (scanning electron – SEM) microscopes (see Chapter 16). Study of scores of quartz grains under the SEM grains from modern environments has revealed that different sedimentary environments impart different assemblages of surface signatures on the quartz grains (Krinsley and Doornkamp, 1973; Le Ribault, 1977; Smart and Tovey, 1981, 1982). Surface analysis of quartz sand grains from the Lower and Middle Palaeolithic site of et-Tabun Cave (Fig. 1.4), for example, was made by Bull and Goldberg (1985). They found that the basal deposits (Layers F and G of Garrod; Lower Palaeolithic – LP) show aeolian and diagenetic surface characteristics. The middle unit, Layer E (LP) is principally aeolian but with signs of marine alteration. Quartz grains in Layers D, C, and B (Middle Palaeolithic) in the upper part, show only aeolian modifications.

Fabric. Sedimentologists and pedologists use the term fabric in different ways. For sedimentologists (e.g. Boggs, 2001; Tucker, 1981), fabric relates to the orientation and packing of grains, which is commonly a function of flow direction. Elongated pebbles, for example, can be oriented in the same direction, either parallel or perpendicular to the flow, depending on the hydraulic characteristics in the environment of deposition. Sand-size particles will commonly be oriented parallel to the flow direction. Another sedimentological concept is packing, which describes the contacts between grains; it is associated with porosity and permeability. Sedimentologists differentiate grain-supported fabric, in which grains are in contact with adjacent ones, from matrix-supported fabric, where coarser clasts (e.g. sand, pebbles) are enclosed within a finer matrix (Fig. 1.5).

FIGURE 1.4 SEM photo of quartz grain from Layer E (Lower Palaeolithic) in Tabun Cave, Israel showing chemical etching of the grain (Bull and Goldberg, 1985). Magnification of grain is 340×. (Photo courtesy of Darwin Spearing.)

On the other hand, soil scientists – particularly micromorphologists – have a slightly broader and more nuanced view of fabric (Bullock et al., 1985; Courty et al., 1989; FitzPatrick, 1993). The most generalized and encompassing viewpoint is that used in the Handbook for Soil Thin Section Description, which we endorse: “Soil fabric deals with the total organisation of a soil, expressed by the spatial arrangements of the soil constituents (sold, liquid and gaseous), their shape, size and frequency, considered from a configurational, functional and genetic viewpoint” (Bullock et al., 1985: 17). This approach to fabric encourages detailed observation of all the components of a deposit, enabling the deconstruction of a soil or sediment into its essential primary (depositional) and secondary (postdepositional) elements (see Chapter 16, lab techniques).

Bedding, Bedforms, and Sedimentary structures. Bedding is an important sedimentary feature, as it reveals information about the environment of deposition as well as postdepositional changes, such as bioturbation, that may erase original traces of bedding. Although in theory, an individual bed accumulated “under constant physical conditions,” (Reineck and Singh, 1980: 95), it is commonly difficult or impossible to recognize such individual events and conditions. A single bed is distinguished from adjoining ones by surfaces generally called bedding planes, which delineate beds of different composition of texture, for example Fig. 1.6. Bedding can be described by a number of criteria, including thickness (Tables 1.4a,b) and shape (Fig. 1.7). A lamina is essentially a thin bed, and generally has uniform composition and smaller areal extent than a bed; it results from a minor fluctuation in flow conditions rather than representing constant physical condition. Individual lamina are bounded by laminar surfaces (Reineck and Singh, 1980).

FIGURE 1.5 Textural and organizational aspects of clasts in fluvial conglomerate, showing features such as sorting and internal organization, including fabric, stratification, and grading. This visualization can be equally applied to other types of deposits (e.g. slope deposits) (modified from Graham, 1988, figure 2.1).

Bedforms are surface morphological features that are produced by the interaction of flow (water or air) and sediment on a bed (Nichols, 1999). Familiar examples are ripple marks as seen on beaches and in streams (see Chapter 5), and dunes (see Chapter 6). Bedding represents sedimentary structures associated with these surface bedforms, which are higher order arrangements or organizations of groups of particles within a sediment. As with grain size, both the bedforms and associated structures have descriptive value, and also furnish information about the environment of deposition, including direction, depth, and intensity of flow. Systematic treatments of sedimentary structures can be found in Boggs (2001); Collinson and Thompson (1989), Reineck and Singh (1980), and only a few will be mentioned here.

FIGURE 1.6 Grouping and subdivision of sedimentary beds according to grain size and sedimentary structure (modified from Collinson and Thompson, 1989, figure 2.2).

TABLE 1.4 (a) Nomenclature used to describe bedding types (adapted from Collinson and Thompson, 1989)

(b) Nomenclature applied to describe thickness characteristics of beds and laminae (adapted from Boggs, 2001)

FIGURE 1.7 Shape characteristics of bedding and laminae (modified from Reineck and Singh, 1980, figure 152).

Current ripple marks, with flow from one direction, are small-scale bedforms, on the order of centimeters. In plan view, they can have different morphologies that include parallel or subparallel, and sinuous to lunate shaped (Fig. 1.8). In cross section, they may be symmetrical or asymmetrical, with crests that range from sharp to flattened (Reineck and Singh, 1980). Internally, stratification is expressed by various forms of cross-bedding that are divided into two basic types, tabular and trough cross-bedding as exposed in three-dimensional view (Fig. 1.8). Moreover, cross-bedding can be produced in a number of different ways in different types of sedimentary environments, such as channels, point bars in meandering streams (see Chapter 5), beaches (see Chapter 7), and sand dunes (see Chapter 6).

Cross-bedding in fine laminae is exemplified by ripple cross lamination. In this case, if the rate of sand addition is larger than the rate of migration of the ripple, elevation of the ripples rises. This process results in the formation of climbing ripples, which point to rapid sedimentation and high sediment input (Nichols, 1999) (Fig. 1.9). Cross-bedding occurs at a variety of scales that range from millimeters to meters. In small-scale forms, cross-beds range from millimeter up to ca 4 cm thick and are usually trough shaped. They are produced by migrating current and wave ripples (Reineck and Singh, 1980). Larger-scale cross-bedding has bedding units that range from >4 mm up to 1 to 2 m in thickness, and can be both planar and trough shaped. They can be found in different environments (e.g. dunes, longshore bars).

FIGURE 1.8 Ripple marks. Block diagrams showing two types of surface ripple bedforms. The underlying sediments are organized into cross beds, of which two types are illustrated here. The upper block illustrates tabular cross-bedding, which is produced by the migration of ripples with straight crests; in the lower block, troughs are formed by the migration of sinuous ripples (Tucker, 1981) (modified from Tucker, 1981, figure 2.21).

FIGURE 1.9 Diagram illustrating climbing ripple cross lamination. The arrow point to the change from in-phase forms at the bottom to climbing forms at the top, which represents decreasing rates of sediment depositon, greater migration, and a reduction of water depth. These features can be produced in the waning stages of deposition on a floodplain.

Other structures found within sediments and soils can be of nondepositional origin and produced by physical, chemical, or biological agents, some partially synchronous (penecontemporaneous) with the original deposition. They include features, such as those produced by freeze-thaw (e.g. ice cracking and frost wedging (Fig. 1.10a)), and desiccation, bioturbation (e.g. burrowing by rodents and soil insect fauna – Fig. 1.10b), and deformation, convolution structures, and load structures (Figs 1.10c,d).

1.2.1.2 Chemical sediments (or nonclastic sediments)

Chemical sediments are those precipitated from solution, and in certain geoarchaeological contexts (e.g. caves), they can form a significant and critical part of the deposits and geoarchaeological story.

In the open-air context, where rates of evap-otranspiration are high, chemical sediments can be related to regional-scale features, such as old lake basins and sediments (e.g. Great Salt Lake and other lakes in the Great Basin, United States; Dead Sea). Many lacustrine sediments in these arid areas commonly tend to be rich in carbonates [calcite – CaCO3, magnesite – MgCO3, and dolomite – CaMg(CO3)2], as well as chlorides (halite – NaCl), and sulfates (gypsum – CaSO4 · 2H2O; anhydrite – CaSO4). The Dead Sea Scrolls, for example, were found in caves developed within Late Pleistocene lacustrine calcareous and gypsiferous marls (Bartov et al., 2002; Begin et al., 2002) deposited in Lake Lisan, the precursor to the modern Dead Sea (Fig. 1.10d). Similar types of deposits in archaeological contexts are not uncommon, and are known from the American High Plains (e.g. Holliday and Johnson, 1989) and Australian Lake Mungo (Bowler et al., 2003) among others.

FIGURE 1.10 Examples of sedimentary structures. (a) Ice wedge formed in bedded and iron stained silts from Normandy, northern France; (b) burrows produced from small rodents at the site of Hayonim Cave, Israel. In addition, the finely bedded and laminated nature of these silty and clay deposits points to deposition in pools of standing water near the entrance; (c) convolution structures in the lighter area of Layers 3/4b/4u at Boxgrove, United Kingdom in which calcareous pond deposits were deformed while they were still wet and undergoing dewatering; (d) soft sediment deformation of finely laminated lake sediments from the Pleistocene Lisan Lake, Dead Sea Region, Jordan Valley; these deformation features are related to earthquakes within the rift valley (Enzel et al., 2000).