AN 850-YEAR RECORD OF HUMAN AND ENVIRONMENTAL CHANGE NEAR THE MISSISSIPPIAN-ERA CITY OF MOUNDVILLE (ALABAMA) FROM LAKE SEDIMENT GEOCHEMISTRY
We retrieved a 1.8-m long sediment core from the 6.2-m deep anoxic basin of Touson Lake to identify past sedimentary changes related to environmental and human disturbance. The sediments were dated using 210Pb, 137Cs, and 14C dating techniques. We measured weight percent organic matter, sorbed metal concentrations, and magnetic susceptibility. Lead (Pb) and zinc (Zn) concentrations were measured because their concentrations in sediments are commonly influenced by human activities (Cohen, 2003). Increases in Pb concentrations around 1400 and 1700 AD suggest that emissions from Mississippian settlements and European settlement are preserved in Touson Lake. Corresponding increases in Zn from 1650 to 1800 AD suggest that other metals, such as zinc and copper, could potentially be used to track inputs from metalworking. In addition, magnetic susceptibility and organic matter measurements record large fluctuations during intervals of mound-building and settlement reorganization in the region, suggesting changes in the amount of erosion during these periods. The Touson Lake record demonstrates that sediments recovered from oxbow lakes in southeast North America could be used to measure past human and environmental changes, which may hold implications for improving both archaeological and paleoenvironmental interpretations.
Cohen, Andrew S. "Geochemical Archives in Lake Deposits." Paleolimnology: The History and Evolution of Lake Systems. Oxford: New York, 2003. 241-55. Print.