Reconstructing Archaeological Sites: Understanding the Geoarchaeological Matrix

By Panagiotis Karkanas and Paul Goldberg

A guide to the systematic understanding of the geoarchaeological matrix

Reconstructing Archaeological Sites offers an important text that puts the focus on basic theoretical and practical aspects of depositional processes in an archaeological site. It contains an in-depth discussion on the role of stratigraphy that helps determine how deposits are organised in time and space. The authors — two experts in the field — include the information needed to help recognise depositional systems, processes and stratigraphic units that aid in the interpreting the stratigraphy and deposits of a site in the field. 

The book is filled with practical tools, numerous illustrative examples, drawings and photos as well as compelling descriptions that help visualise depositional processes and clarify how these build the stratigraphy of a site. Based on the authors’ years of experience, the book offers a holistic approach to the study of archaeological deposits that spans the broad fundamental aspects to the smallest details. This important guide:

• Offers information and principles for interpreting natural and anthropogenic sediments and physical processes in sites
• Provides a framework for reconstructing the history of a deposit and the site
• Outlines the fundamental principles of site formation processes
• Explores common misconceptions about what constitutes a deposit
• Presents a different approach for investigating archaeological stratigraphy based on sedimentary principles

Written for archaeologists and geoarchaeologists at all levels of expertise as well as senior level researchers, Reconstructing Archaeological Sites offers a guide to the theory and practice of how stratigraphy is produced and how deposits can be organised in time and space.

• Language: English
• Publisher: Wiley
• Release date: Jun 11, 2018
• ISBN: 9781119016410

Book preview

Preface

Why did we decide to write another geoarchaeology book? That is a good question in light of the fact that geoarchaeology is finally becoming a mature discipline. We are both geologists by training, close friends, and we communicate by Skype, telephone, and at conferences. Yet, ironically, we penecontemporaneously and independently realized that archaeological deposits have been overlooked as valuable and necessary resources of data in the archaeological record. We came to the conclusion as practicing geoarchaeologists – with perhaps too much field experience – that the ultimate context of archaeological objects is the surrounding sedimentary matrix and, as a consequence, the anthropogenic and geogenic depositional processes that form it. Such a discovery is not really new, but in searching through the literature we discovered that there is no systematic or in‐depth treatment of the topic – the geoarchaeological matrix – and how it can be thoroughly squeezed to provide a wealth of latent information that can be used to reconstruct geological and human histories at archaeological sites.

This book focuses on basic theoretical and practical aspects of depositional processes in archaeological sites and discusses in depth the role of stratigraphy, which fundamentally is an intellectual construct that helps us envision how deposits are organized in time and space. The book is constructed in such a way as to offer archaeologists and geoarchaeologists – whether senior level researchers or students at the beginning of their studies – an inventory of information and tools that they can use to recognize depositional systems, processes, and stratigraphic units that will enable them to realize and interpret the stratigraphy of a site in the field. We feel that this approach is a constructive way to further the dialogue between archaeologists and geologists.

In order to achieve this broad goal, we provide examples, along with illustrations and drawings, photographs and in‐depth descriptions that will help the reader visualize depositional processes and how these build the stratigraphy of a site. In addition, we include some of the practical tools that we have used over a number of years of working closely with archaeologists in many types of sites and localities. In sum, we have tried to offer a holistic approach to the study of archaeological deposits, from the broad fundamental aspects to the details. We hope that we will convince the reader that deposits are artefacts on a par with other objects of the archaeological record. After all, they furnish the essential aspect of the sedimentary matrix that encircles archaeological objects and features from virtually any site anywhere on the globe.

Acknowledgments

The notions that we have developed here would not have been possible without the participation of our friends and colleagues in the field over a lot of time during our professional lifetimes. It is they who put us on to thinking of these issues, whether intentionally or not. They are too numerous to name individually, but a few stand out and are listed alphabetically here:

V. Aldeias, T. Arpin, G. Avery, O. Bar‐Yosef, F. Bordes, C.B. Bousman, K.W. Butzer, M. Chazan, M. Chech, A. Belfer‐Cohen, B. Byrd, E. Chambers, M.B. Collins, N.J. Conard, M.‐A. Courty, M. Dabney, H.L. Dibble, N. Efstratiou, W.R. Farrand, N. Fedoroff, C.R. Ferring, N. Goren, N.A. Goring‐Morris, K. Harvati, D.O. Henry, J.F. Hoffecker, V.T. Holliday, E. Hovers, G. Huckleberry, Z. Jacobs, A.J. Jelinek, S. and E. Kaplan, D. Killick, N. Kyparissi‐Apostolika, S.L. Kuhn, H. Laville, T.E. Levy, R.I. Macphail, R.D. Mandel, C.E. Miller, C. Mallol, C.W. Marean, S.P. McPherron, L. Meignen, S.M. Mentzer, A. van de Moortel, M. Morley, L.C. Nordt, E. Panagopoulou, A. Pérez‐Juez, W. Parkinson, K. Pavlopoulos, R.G. Roberts, C. Roos, A.M. Rosen, D. Sandgathe, H.P. Schwarcz, R. Shahack‐Gross, L.A. Schepartz, S.C. Sherwood, J.D. Speth, J.K. Stein, M.L. Stiner, C.B. Stringer, L.A. Sullivan, A. Turq, G. Tsartsidou, B. Vandermeersch, S. Villeneuve, S. Weiner, I. Whitbread, R. White, J.C. Woodward, H.T. Wright, J.C. Wright, and A. Yair.

We owe special thanks to Jamie Woodward, Vance Holiday, Ruty Shahack‐Gross, Steve Weiner, Rich Macphail, Bill Parkinson, and Amalia Pérez‐Juez for their insightful and constructive suggestions on early versions of various chapters. They really helped a lot.

Over the years we have received institutional support that in one way or another (providing funding or the availability of intellectual or material resources) has ultimately made this work possible from (in no particular order) the Alexander von Humboldt Foundation, the American School of Classical Studies in Athens, Boston University, the Care Foundation, Ephoreia of Palaeoanthropology‐Speleology (Ministry of Culture, Greece), Harokopio University (Greece), the Cave Research Foundation, the Geological Society of America, the Society for American Archaeology, the Archaeological Institute of America, Harvard University, Simon Fraser University, the French Foreign Ministry, the French CNRS, the Hebrew University of Jerusalem, the University of Michigan, the University of Texas at Austin, the University of Tübingen, the University of Wollongong, the US National Science Foundation, the Malcolm W. Wiener Foundation, the National Geographic Society, and the LSB Leakey Foundation.

Abbreviations

BA Bronze Age EBA Early Bronze Age ESA Early Stone Age LBA Late Bronze Age LP Lower Palaeolithic LSA Later Stone Age MBA Middle Bronze Age MP Middle Palaeolithic MSA Middle Stone Age PPL plane‐polarized light UP Upper Palaeolithic XPL crossed polarized light

I

Introduction: A Depositional Approach to the Study of Archaeological Excavations

Look at Figure I.1. It shows two photographs from archaeological sites in Greece that we have studied: Figure I.1a is a profile of Middle and Upper Palaeolithic layers from the site of Theopetra and Figure I.1b is from post Late Roman to recent deposits in the southern part of Ancient Corinth. Without knowing anything about the sites and without any geological training, an observer is immediately struck by the complexity of these stratigraphic sequences. How do we make sense of these deposits and how do we incorporate this information into our understanding of the significant archaeological findings from these two important localities? That is the subject of this book.

Figure I.1 Profile photographs from (a) Medieval Corinth and (b) Palaeolithic Theopetra, Greece (from Karkanas and Goldberg, 2017b). Note the complexity in both despite the vastly different ages. Scale in (a) = 3 m and in (b) = 1 m.

Theoretical Issues

It is probably the only consensus in archaeology that stratigraphy is ‘the jugular vein of archaeological practice’ (McAnany and Hodder, 2009a,b). Stratigraphy has many definitions and is defined here as the spatial and temporal arrangement of depositional units. Regardless of the wording, it provides the framework of reconstructing the history of a site. Stratigraphic units, layers, features, cuts, or strata – also called context or locus according to different archaeological schools of thought – are made of sediments that are the product of natural processes and anthropogenic activities, and are deposited on the surface of the earth. Archaeological deposits – those that contain artefacts and anthropogenic products – are thus by their very nature forcibly part of the archaeological record. In order to interpret the archaeology of a site correctly, it is a prerequisite to understand how stratigraphy is built and how the strata are formed. This book is about how we recognize the processes and activities that produce the deposits of a site and how these are organized in time and space to form a stratigraphic sequence.

Our personal understanding of stratigraphy and archaeological deposits is based on a conceptual model, which is described by a few fundamental propositions:

A site is a three‐dimensional arrangement of artefact‐bearing deposits, therefore the fundamental unit of a site is the deposit, not the artefact or the pattern of the artefacts.

The deposits have accumulated by natural or anthropogenic processes or a combination of these.

The fabrics of the sediment are indicative of the different processes involved in their formation.

Traditional artefacts (pottery, flints, etc.) are fabric elements within archaeological deposits.

Architectural features (e.g. walls, mosaics, etc.) may have their own typology and internal stratigraphy but the relationship between construction phases and the surrounding artefacts is mediated by the enclosing deposits.

Natural deposits in a site may have a cultural meaning (e.g. sediments trapped within aqueducts).

All elements that form a deposit should be treated as having equal importance with the traditional items of the archaeological record (architecture, pottery, lithics, objects, etc.) in the study of a site.

Time resolution is essentially determined in the field by how finely we can recognize the vertical and horizontal extent of individual stratigraphic units, which are the proxies for activities and processes. Similarly, such units should be recognized and recorded only during excavation and not after.

For most prehistoric archaeologists, the above principles are known and generally accepted because prehistory traditionally evolved in parallel with geology. But this is not always the case, particularly for those who investigate the archaeology of historical periods, which traditionally treats archaeology as history, with a reliance on texts. Excavating a site by utilizing the above principles is not straightforward, as it demands knowledge of natural and anthropogenic sedimentary processes. However, most archaeology programs in academia do not include basic sedimentology courses. The outcome is that most archaeologists acquire knowledge of stratigraphy through practice in the field and detailed observations of what they see. The question that underlies this reality is therefore can everyone ‘see’ all stratigraphic boundaries (or interfaces) in an excavation? Is it a matter of experience, knowledge, or talent?

In the following discussion we will show how stratigraphy is produced, and examine the fundamental elements and attributes that create it. At the same time, we will touch on common misconceptions about what constitutes a deposit, issues related to the nomenclature used, and the different approaches to investigating archaeological stratigraphy.

The Formation of Stratigraphy

Human earthen structures and anthropogenic sediments in general (floors, occupational surfaces, middens, fills, pits, mounds, etc.) have a materiality that, at an initial level, can be described and understood by using concepts and methods derived from the natural sciences, such as geology; in fact, no new terminology is required. The deposits of the site consist of materials that are overwhelmingly particles (clasts) of minerals and rocks. It is puzzling to assume that a unit can be described without referring to the fundamental attributes of sediments, mainly grain‐size distribution, sorting, roundness, orientation, grading, colour, and ultimately the fabric produced by the organization of the attributes. All these attributes are not neutral and meaningless, or simply geometric features. The mineralogical content and chemistry are also fundamental properties of an archaeological deposit as they provide information about its source and post‐depositional alteration.

Knowledge of the fundamental properties of human earthen constructions is a prerequisite for interpreting this aspect of site stratigraphy. On one hand, these properties serve to convey descriptive criteria to interested researchers, but more importantly they transmit information of the processes that produced them. In the realm of natural sedimentary basins, these descriptive terms imply certain depositional environments. For example, rounding is caused by abrasion during transport (e.g. streams) or by reworking by wave action, for example; transport does not fundamentally reduce the size but does selectively sort material (Folk, 1974). Each transporting medium produces certain types of sediments because the dynamics of transport and deposition are different.

In the realm of a site, human processes do not produce such attributes, which even in earthen constructions are mostly inherited from the original material at the natural source, but now organized in a different way through a ‘human filter’. Anthropogenic activities admittedly produce new organizations, but the essential building blocks are the same. Human activities are no different in representing the elemental dynamics of transporting and depositing materials through actions such as trampling, digging, dumping, kneading and pugging, sweeping, brushing, discarding, and placing. Therefore, rounding can be produced by continuous trampling and scuffing, and brushing and sweeping may bring about sorting and lamination. Similarly, dumping may cause grading within the deposits, and pugging will produce orientation, whereas discarding may lead to clustering of grains (see Chapter 3). Some activities do produce new materials, such as burning (ashes) and other pyrotechnological activities (ceramics). Nevertheless, their accumulation and final deposition on the earth’s surface is the product of the actions described above.

All the aforementioned attributes are the building blocks of every description of what is called a lithostratigraphic unit. These units are bounded by contacts, and contacts are the product of changes in the attributes, whether they be differences in composition or the way that they are organized. Sometimes, the contact itself records a change in the attributes, although they are rarely discerned as such in the field (further discussed in Chapter 4). However, all these attributes cannot be identified without knowing what to look for, and what they might mean. As is so often the case, without understanding how things can form – in this case, units – it is difficult and challenging to discern and describe stratigraphic entities. In addition, all material and earth science studies in an archaeological site use descriptions derived from physical sciences, mainly mineralogy, petrology, sedimentology, and soil science (pedology). During the last two decades geoarchaeological studies have made significant inroads toward archaeological interpretation of urban sites by providing microstratigraphic histories within rooms, and data on the life of buildings and the use of space (e.g. Matthews, 2005; Matthews et al., 1996; Shahack‐Gross et al., 2005; Macphail and Crowther, 2007; Macphail et al., 2007; Milek and Roberts, 2013; Karkanas and van de Moortel, 2014). It will be confusing to have a separate and different system of description for archaeological deposits, and another one for geological ones.

Bear in mind that observation is not independent of theory. What we see is not objective because it is based on a conceptual model of organizing images (Hanson, 1958); in our case, sediment attributes and structures can be organized in a meaningful way, that is, stratigraphy, only if one has a conceptual model of what to look for. Therefore, it is not so much about interpretation of what we see but rather the stratigraphic organization of the ensemble of lines, surfaces, and features that are revealed in the field. Stratigraphic organization is not an object that can be simply described in terms of shape or colour; it is a concept gained after data are evaluated (Hanson, 1958). Stratigraphic theory also maintains that there is a hierarchy among the sedimentary features, which are decisive in correctly understanding a sequence.

Therefore, not every linear feature in the profile or surface on a plan view is a contact or interface. This is important because determining contacts implies other meaningful things rather than just a geometrical feature. It is the appreciation of this conceptual and holistic model of depositional processes and systems that is lacking from most archaeological approaches to stratigraphy. As a consequence, students of archaeology face a frustrating and perplexing task in trying to properly understand a stratigraphic sequence, simply because most do not have background knowledge of depositional and post‐depositional processes.

The above discussion highlights that the weight should be shifted from constructing stratigraphy to acquiring knowledge of depositional processes that produced it. At this point, three issues should be discussed further:

Can anthropogenic depositional processes be described in the same way as natural (geogenic, pedogenic, biogenic) ones?

Except for disentangling stratigraphic relationships, what else is gained when someone succeeds in comprehending the depositional processes in an archaeological