Investigation of Stratigraphic Manifestations of Younger Dryas Climate at Paleoindian Sites in North America

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Approximately 11,000 years ago a wide range of North American large fauna went extinct over a short time period and scientists wish to understand the cause. Two main theories have been proposed: one invokes climate change and accompanying vegetation shifts. The other notes the presence of Paleoindian hunters and gatherers and sees hunting as the primary cause. In his prior work Dr. Vance Haynes has recognized the presence of a distinct dark organic strata which is present in many sites in the US West, Southwest and High Plains. It is extremely rare to find such a well defined horizon over this large an area and its presence implies a major climatic event. Artifacts associated with the Clovis culture are found under the horizon but never within or above it. Stone tools from the succeeding Folsom group occur only in or above the horizon. This fact leads Dr. Haynes to speculate that the organic layer is in fact synchronous across sites and was deposited in a very short time period. He associates the layer with the Younger Dryas cooling event, a period of major climatic change. He also notes that this coincides with a period of maximum faunal extinction. Unfortunately the organic soil horizon is not well dated and with NSF support Dr. Haynes will visit a series of sites which contain the horizon and are also important because of the archaeological and paleontological materials they contain. He will record the stratigraphic sequence and collect suites of materials for radiocarbon dating. Specific organic compounds will be isolated for stable isotope analyses to determine relative amounts of C3 vs. C4 vegetation. In this way floral change can be both noted and dated. This research is important because it will provide precise dates for past climate and environmental change in North America. This will refine the framework for understanding changes in both human behavior and faunal extinction.