Geoarchaeology is a multidisciplinary field of study that applies the theories and techniques of the geosciences to archaeology. It draws on techniques and approaches from geomorphology, sedimentology, pedology, stratigraphy, and geochronology to interpret sediments, soils, and landforms in archaeological investigations to inform archaeological and chronological knowledge and thought. Geoarchaeologists study the natural physical processes that affect archaeological sites such as geomorphology, for example, and their effects on buried sites and artifacts post-deposition. Geoarchaeologists' work frequently involves studying the soils and sediments of archaeological sites and the surrounding region to inform archaeological research. Geoarchaeologists also frequently use tools such as computer cartography, geographic information systems (GIS), and digital elevation models (DEM) in combination with disciplines from human and social sciences and earth sciences to inform their investigations and interpretations of sites. Geoarchaeology is important because it informs archaeologists about the geology of the site, including the geomorphology of the soil and sediment. It also places artifacts and landforms present in the site into relative and absolute temporal context to better inform archaeological interpretations. Geoarchaeology is considered a subfield of environmental archaeology because it utilizes similar concepts and techniques and applies them to address the same archaeological problems.
Objectives There are three main objectives in most kinds of geoarchaeological investigations:
To place archaeological sites and their contents into their temporal context. This is done through the analysis and interpretation of the stratigraphy of the site and by using absolute dating techniques. To understand the natural processes that create archaeological sites. To develop landscape reconstructions of the area where the site was located to aid in interpretations of the site.
History and Development Geoarchaeological concepts and techniques have been used in both geological and archaeological investigations since the 18th century. However, scientists began to use the methods and techniques of the geosciences to interpret the archaeological record more commonly in the middle of the 19th century. The application of stratigraphic principles to archaeological sites stems from the work of Niels Stenson (aka Nicolas Steno) in 1669 and James Hutton in 1788. Stenson’s work developed and provided a basis for the principles of superposition and original horizontality, two of the core concepts in both geoarchaeology and archaeology. Hutton’s work led to significant conclusions in the 1850s about how old the human race is. Geoscience concepts continued to be applied to archaeological investigations in this way for the next few decades, until the early 1900s, when the application of these principles to archaeological sites became more refined with the addition of more specific field and lab techniques for studying past environmental conditions and material analysis. Geoarchaeology, as we know it today, developed as a subfield of archaeology in the 1970s-1980s through the work of multidisciplinary teams applying geoscience field techniques to their studies. Innovations in dating technology in the 1940s enabled more accurate absolute dates to be obtained from many kinds of archaeological sites, which demonstrated the value of geoscience concepts and techniques to archaeology.
Techniques Used
Monolith Sampling Monolith sampling is a geoarchaeological sampling technique that involves collecting sample cores from a section of an archaeological site to analyze and detect the buried processes that have affected the site. Narrow metal tins are hammered into the section, either by hand or by using machinery, in a sequence to collect the complete profile of the site for study. If more than one tin is needed, they are arranged in offset and overlapping positions so the complete profile can be rebuilt, typically off-site in laboratory conditions.
Loss on Ignition Testing Loss on ignition testing for soil organic content is a technique that measures the organic content of soil samples. Samples taken from a known location in the profile, collected by column sampling, are weighed and placed in a furnace oven, which burns off the organic content. The cooked sample is then weighed again, and the resulting loss in weight of the sample indicates the organic content in the profile at a given depth. This technique is often used to detect buried soil horizons that may not be visible to the naked eye. Ancient land surfaces, especially from the prehistoric era, can be difficult to discern, so this technique is useful for evaluating an area's potential for prehistoric surfaces and archaeological evidence. Comparative measurements down the profile are made, and a sudden rise in organic content at some point in the profile, combined with other indicators, is strong evidence for buried surfaces.
Near-Surface Geophysical Prospection Geophysical archaeological prospection methods are used to non-destructively explore and investigate possible archaeological sites buried in the subsurface. Commonly used methods include:
Magnetometry Ground-penetrating radar Earth resistance measurements Electromagnetic induction measurements (including metal detection and Magnetic susceptibility surveys) Sonar (sidescan, single-beam or multibeam sonar, sediment sonar) in underwater archaeology Less commonly used geophysical archaeological prospection methods include:
Reflection or refraction seismic measurements Gravity measurements Thermography
GIS in Geoarchaeology GIS (Geographic Information Systems) has been widely used in archaeology since the 1980s. In archaeological contexts, GIS is mainly used for managing information and for spatial analysis. Spatial analysis is its most common application in archaeology, followed closely by heritage management. GIS is also commonly used to help gather and analyze archaeological data.
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