YOUNGER DRYAS RECORD IN DEVILS LAKE, WI

Devils Lake, Sauk County, Wisconsin, is a remarkable scientific resource. It was formed in an ancient quartzite valley cut through the south limb of the Baraboo Syncline. The valley was blocked at each end by the terminal moraine of the Wisconsinan Green Bay lobe. The lake sediments are ideal for pollen analysis. The original cores were obtained in 1978, and a preliminary report was included in the 1982 Quaternary History of the Driftless Area prepared for the Midwest Friends of the Pleistocene by the University of Wisconsin-Extension, Geological and Natural History Survey, Field Trip Guide Book 5.

The age data in the report were based on 14C dates from bulk analysis of the sediment, but later AMS dates showed the original dates in the lower portion of Devils Lake were about 1000 years too old. While many Midwestern pollen diagrams only display percentage data, the Devils Lake study also measured pollen abundance in grains per gram of sediment as well as pollen influx in grains per cubic centimeter per year. These absolute measures show that the Younger Dryas interval in Devils Lake very closely matches the timing measured in the Greenland ice cores. Although percentage pollen data suggest that spruce pollen in the Midwest increased during the Younger Dryas interval, the Devils Lake data show that spruce pollen abundance was also drastically reduced during the Younger Dryas, but not as much as were the other taxa.