Large-scale and Site-specific Research in Geoarchaeology

Geoarchaeology is conducted on large and small scales. Regional or large-scale geoarchaeology reconstructs landscape and paleoenvironmental history. Smaller-scale projects in geoarchaeology are more site specific and focus on the stratigraphy and features of an archaeological site.

Large-scale geoarchaeological projects might focus on the segment of a river valley. Such a project may reconstruct the landscape history of the river valley by establishing the sequence of deposition, erosion, and soil formation from the period just prior to human occupation. The archaeological record of this portion of the valley could then be placed within this landscape history for relative dating. In addition, within this landscape reconstruction, it would then be possible to interpret the natural formation processes acting at each archaeological site. Finally, the preservation of the archaeological record could be evaluated and the impact of landscape history could be analyzed for its potential influence on settlement patterns. As a result of this type of project, a geoarchaeologist can formulate predictive models for locating archaeological sites and contribute inputs into the effect of landscape on settlement patterns.

For example, recent geoarchaeological work has been conducted in Argentina by the author on a large river valley on the border between Patagonia and the Pampas. Extensive fieldwork included survey, detailed stratigraphic recording, analysis of the geomorphology, recording of archaeological sites, and collection of samples for geological analysis, radiocarbon dating, and optically stimulated luminescence (OSL) dating.

As a result, it was possible to reconstruct the landscape of a 150 km segment of this valley from its initial formation and place the stratigraphy and each land-form into a chronological framework from the Late Pleistocene through the Holocene. As a result, it was then possible to place the known archaeological record into this chronological framework and landscape context. It was also possible to evaluate the preservation and natural formation processes of each known archaeological site. In addition, a predictive model was constructed for the location of archaeological sites for each time period based on this landscape reconstruction. In short, archaeological sites from the Middle Holocene will be found buried in Middle Holocene landforms on Middle Holocene land surfaces, etc. Now it is also possible to interpret how the landscape history of this valley could have had an influence on past human settlement patterns and there are very good indications that abrupt changes in the river course also contributed to shifts in settlement.

Site-specific geoarchaeology has now become very common. A geoarchaeologist is called in to help interpret the stratigraphy and answer specific research questions. For example, micromorphological analysis could be used to investigate postdepositional processes which occurred at a site. Micromorphology is a geoarchaeological method of analyzing thin sections of sediments using microscopy. Micromorphology can be used to decipher the microstratigraphy and reveal discrete traces of human behavior that would otherwise be destroyed through physical and chemical analysis or not identified macroscopically from field observation (i. e., through stratigraphic recording). Such discrete archaeological features found in thin section can be potentially important to large-scale archaeological interpretations at archaeological sites. In addition, it is possible to locate geological and pedological features that can be important for understanding the geoarchaeology of a site, which in turn forms the basis for archaeological interpretations. Geoarchaeological micromorphology became more prominent in the late 1980s and early 1990s after the publication of Soils and Micromophology in Archaeology by M. Courty, P. Goldberg, and R. Macphail in 1989. This handbook formalized micromorphological analysis at archaeological sites and illustrated the value of this technique through specific case studies.

For example, a micromorphological analysis was recently conducted at a North American Clovis site by the author. Samples were collected from the site in order to analyze the degree of groundwater impact on archaeological evidence, the extent that soil formation processes have affected a site, the presence and extent of any bioturbation even on the microscale, and to search for any evidence of discrete occupational surfaces. As a result of this analysis, although minor postdepositional processes did occur at this site, the site is fully intact and has not been altered significantly by these processes to affect archaeological interpretations. Both scales of research in geoarchaeology are crucial for evaluating the archaeological record.