In archaeology, sediments can be used as artefacts. The aims of this thesis are to critique the role of geoarchaeology as a key methodological tool within archaeology, and to demonstrate its capacity to contribute to a deeper understanding of past social and socio-environmental behaviours. These aims are predicated on the principle that analysis of past human behaviour can be enhanced through examination of the sedimentary record as an archaeological artefact, in which the physical, geological, biological and chemical qualities of an archaeological site reflect and therefore provide implications for human behaviour, environmental change, and human-environment relationships. The approach of this research, therefore, is to focus on the sedimentary record of archaeological sites to illustrate how social and human behaviour regarding interactions with the environment and the construction and development histories of the sites represent a mutual exchange between environment and society of prehistoric people.
The aims are addressed through site-specific geoarchaeological case studies within an ongoing archaeological program in northeast Thailand. Sediment samples were selected from the two prehistoric archaeological sites of Ban Non Wat and Nong Hua Raet, situated in the Mun River valley of north-eastern Thailand. The sediments represent different cultural layers and features of the prehistoric occupation, including controversial ‘hard floor’ surface sediments. This research addressed six specific archaeological problems, to contribute to the broader archaeological understanding of the site, and demonstrate the applicability of geoarchaeology for improving archaeological understanding.
1. Sediment chemistry. Identification of specific chemical signatures of both anthropogenic and non-anthropogenic sediments associated with the sites contribute to understanding the nature of human activities associated with these sediments. Chemical signatures are identified for the stratigraphic units of floodplain alluvium, archaeological sediments, spoil, channel infill sediments, sand, hard floor surface and general spit sediments. These results are compared with other site types in the same archaeological context, to prepare a regional data set of important chemical elements. This provides baseline data for future studies. In relation to specific issues, the results provide identification of the former human activities associated with the ‘hard floor’ surfaces.
2. Sedimentological characterisation. Full sedimentological description of occupation layers allows characterization of the different stratigraphic layers of human occupation. In particular, this analysis provides evidence of the modification of soils by anthropogenic activities.
3. Geochronology. The chronology of the cultural layers was further developed using AMS radiocarbon dating to supplement existing data, specifically to examine the dating of the end of the Iron Age occupation. The results lend support to the existing chronological framework of the study area, and suggest that the end of the Iron Age in the Mun River valley is better defined as a gradual transition from dispersed rural settlements to a more concentrated urban style settlement.
4. Siliceous microfossil analysis. Analysis of siliceous microfossils – phytoliths, diatoms and sponge spicules – provides insight into past environmental conditions and natural resources. The evidence of rice phytoliths confirms the presence of agricultural activity from the beginning of the settlements, expanding understanding of that agriculture by providing novel evidence for rice processing at these sites. This evidence sheds new light on the behaviour of the prehistoric people occupying the sites. Diatoms and sponge spicules provide evidence of the close association of water features in association with the occupation site. The diatom evidence suggests that the floors were constructed using nearby channel and floodplain sediments.
5. Fatty acids. In a ground-breaking study for the region, prehistoric fatty acids have been extracted from the ‘hard floor’ sediments, providing new knowledge to the regional archaeology. The study tested current analytical techniques, and demonstrates the preservation of fatty acids in the prehistoric archaeological sediment of these sites. The results confirm that the ‘hard floor’ sediments represent domestic living floors or activity areas of the prehistoric inhabitants, upon which, specifically, meat and other food was processed.
6. Raman spectroscopy and automated chemical and sedimentological analysis. The final case study introduces, tests and demonstrates a novel technique to geoarchaeology. The state-of-the-art Morphologi G3SE-ID Instrument system is a fully automated, quick and easy technique to analyse sediments. The instrument is used in this study to identify morphological parameters and chemical signatures of sediment particles. Compared with the results from conventional analyses (previous studies, above), these findings provide support of both the anthropogenic origin of the ‘hard floor’ sediments and the prehistoric use associated with them.
Sediments can be regarded as artefacts to reconstruct past human behaviours. This thesis discusses the geoarchaeological methods of sediment analysis to interpret the human activities in their occupation sites. Geoarchaeological methods of sediment chemistry, sedimentological characterisation, geochronology, siliceous microfossil analysis, fatty acid analysis, Raman spectroscopy and automated chemical and sedimentological analysis focused on the sedimentary records of the site.