Stable Isotope Analysis of Busycon sinistrum to Determine Fort Walton-Period Seasonality at St. Joseph Bay, Northwest Florida
Degree Granting Department
Nancy M. White
Gregory S. Herbert
Florida Archaeology, Gastropod, Mississippian, Sclerochronology, Shell midden
Recent archaeological investigations indicate that coastal Fort Walton cultures in the St. Joseph Bay region of northwest Florida emphasized marine and estuarine foraging. These late prehistoric (A.D. 1000-1500) peoples collected fish, shellfish, and other aquatic resources. At the Richardson's Hammock site (8Gu10), radiocarbon-dated to about A.D. 1300, as at dozens of other shell middens around this salty bay, large gastropods were a major subsistence component. This adaptation is in sharp contrast with that of contemporaneous inland Fort Walton societies, who relied on maize agriculture. It is unknown whether coastal groups represent separate hunter-gatherer-fisher populations or seasonal migrations by inland farming villagers. This thesis research uses stable oxygen and carbon isotope analysis on lightning whelks (Busycon sinistrum) to determine the seasonality of Fort Walton foraging, and compares the environment of prehistoric St. Joseph Bay with that of the modern bay. Oxygen isotope profiles suggest that shellfish collecting was relegated primarily to the summer months, producing a scheduling conflict with the primary growing season for maize in northwest Florida. Thus, it is argued that coastal and inland Fort Walton probably represent separate culture groups. The relationship between d18Oshell and d13Cshell indicates similar environmental and climatic conditions between prehistoric St. Joseph Bay and today. However, modern whelks are depleted in d13C compared to Fort Walton whelks, which reflects both twentieth century CO2 emissions and years of dredging and wastewater pollution entering the bay.
Scholar Commons Citation
Harke, Ryan Michael, "Stable Isotope Analysis of Busycon sinistrum to Determine Fort Walton-Period Seasonality at St. Joseph Bay, Northwest Florida" (2012). USF Tampa Graduate Theses and Dissertations.
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