Sedimentary Origins of an 8000 year-old Rock Shelter through Particle Size Analysis and X-Ray Diffraction of Clays
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This geoarchaeological study was designed to determine the sedimentary and anthropogenic origin of an 8000 year-old Warren Point Sandstone rockshelter on the Domain of the University of the South following a 2.5 month excavation during the summer of 2009. Analyzed sediments were collected at 10cm increments from an excavated trench 70 cm in depth (7 samples). We detected a high clay percentage (20-40%) throughout the trench using Particle Size Analysis (PSA). PSA showed an average composition of 62% sand, 7% silt, and 31% clay; sand was shown to be distributed relatively equally in all samples, whereas silt and clay distribution show a slight increase with depth. The samples at each depth were x-ray diffracted at 1 hour each to conduct a mineralogical analysis of the clay fraction. We detected kaolinite, montmorillonite and illite as well as additional secondary minerals. Preliminary results from repeat x-ray diffraction of samples at 22 hours each shows a much more quantifiable clay type distribution. At present, it seems likely that the clays may have an anthropogenic origin. Additional research is needed to quantify the influence of clays from the rock surrounding the shelter.