Artefact Preservation in Saturated, Tropical Cave Sediments
Channel: Recording Archaeology
Date: 2017-11-09

Artefact Preservation in Saturated, Tropical Cave Sediments: Constraining Site Formation Processes in the Humid Tropics Through Experimental Reconstruction of Sedimentary Palaeoenvironments 

Archaeological site formation processes active in the Pleistocene caves of the humid tropics are currently poorly resolved. This uncertainty impacts archaeological understandings of settlement patterns, subsistence strategies and hominin interactions in Southeast Asia, a region increasingly at the forefront of Palaeolithic research. Sedimentary environments inside caves have been a focus of geoarchaeological research in temperate latitudes, but our current understanding of post-depositional alteration of archaeological material within these environments is based largely on field observations. Post-depositional changes are often claimed to be accelerated by tropical climates, but these claims are difficult to relate conclusively to observed sedimentary features. To generate much-needed reference data and bolster our understanding of diagenetic processes in tropical regions, we are conducting experiments that involve the construction of stratigraphic sequences as analogues for sedimentary palaeoenvironments in tropical caves. A basal layer of sand provides a surface upon which archaeological material is distributed, representing a typical occupation deposit associated with modern humans. Each stratigraphic sequence has two, virtually identical sets of archaeological “artefacts.” Guano is deposited on top of this ‘cultural layer,’ and the sediments are saturated with water, simulating the anoxic, waterlogged conditions inferred from micromorphological analysis of excavated sites. Electrochemical data will be collected to characterise changing sedimentary environments, while a combination of analytical techniques, including X-ray analyses, vibrational spectroscopy and electron microscopy, will be used to observe the progression of mineralogical changes, organic taphonomic processes and element transport. Thin sections will be made to link the chemical and physical alterations affecting the excavated assemblage to visible micromorphological features. Excavations will be carried out at regular intervals, and include control samples, to allow for comparisons of diagenetic processes through time and under different environmental conditions. In this paper we will discuss our initial experimental results, together with a discussion of their broader implications.

Conor McAdams, Richard “Bert” Roberts, Mike W. Morley Centre for Archaeological Science, University of Wollongong, Australia