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Date Submitted

Spring 4-14-2015

Research Mentor and Department

Alex Bradley




The largest settlement of the Mississipian Native American society, Cahokia Mounds, was inhabited from approximately 800 – 1350 CE. To better understand the environmental context of Cahokia’s decline, we attempt to constrain widespread agriculture associated with this settlement. We examine stable carbon isotopes in leaf waxes through lake sediment cores taken from Horseshoe Lake (Madison County, IL), about a mile away from the Cahokia site. By measuring the relative 13C content of leaf waxes through the sediment core, we can detect shifts coincident with the onset and decline of agricultural land use by the Cahokian settlement. We constructed a maize contribution model using our 13C/12C values to place numerical constraints on maize contribution to the record. Our results suggest maize agriculture peaked in the area at 1037±80 CE, comprising between 4% and 53% of the terrestrial plant community. This coincides with the largest expansion of the Cahokia settlement suggesting that maize agriculture was linked to the enlargement of the settlement.

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