ABRUPT ECO-CLIMATE TRANSITIONS DURING PRE-CLOVIS OCCUPATION IN THE SOUTH-CENTRAL U.S (Invited Presentation)

Discovery of the Debra Friedken pre-Clovis site along Buttermilk Creek in central Texas has led to renewed interest in eco-climate environments during the late Pleistocene. For the 20 ka to 10 ka interval we compiled terrestrial records for the south-central U.S. from bog pollen, stable C isotopes of buried soils, speleothems, noble gases of groundwater, and time slices of temperature and rainfall from general circulation models. We coupled these terrestrial data with marine isotopic records from the Gulf of Mexico (GOM) to reconstruct an evolving eco-climate record of the region.

The warming trend that followed the last glacial maximum began ~17 ka and was accompanied by a mosaic of spreading C4 grasslands and woodlands. The largest and most significant meltwater pulse entered the GOM between ~15.5 and 13.0 ka (mwp-1a), apparently in response to Bølling-Allerød warming in high latitudes. This event reversed the deglacial warming trend in the region as rainfall decreased and mixed C3/C4 grasslands emerged at the expense of woodlands. During the Younger Dryas, temperatures increased again as meltwaters in the GOM were redirected to the St. Lawrence Seaway and Arctic Ocean. C4 grasslands and a mosaic of woodlands again emerged.

Climate conditions during the terminal Pleistocene in the south-central U.S. were chaotic and non-analog because of lower sea level, rapidly rising summer insolation, greater seasonality, lower pCO₂, and meltwater pulses. It is during the major meltwater pulse in the GOM (mwp-1a), however, that pre-Clovis people occupied Buttermilk Creek in central Texas. Winter rains emanating from a dominance of westerly air flow accompanied by warm and dry summers indicate that occupation occurred in a climate unlike today. The Clovis, and then Folsom people inhabited the region during the rapid Bølling-Allerød to Younger Dryas transition when meltwater was diverting to the North Atlantic forcing higher temperatures, summer monsoonal rainfall, and possibly the mass extinction of megafauna. This investigation shows that more work is needed to better understand the influence of shifting eco-climates on potential settlement patterns and subsistence strategies during the peopling of the Americas.