VEGETATION AND CLIMATE OF THE LAST GLACIAL INTERGLACIAL CYCLE IN SOUTHERN ILLINOIS, USA

Raymond Basin and Bald Knob Basin, Montgomery County, Illinois, formed as kettles during Illinoian time. Fossil pollen from these basins pro vides information on vegetation and climate during the last glacial-in terglacial cycle. The pollen profile at Raymond Basin contains an expa nded Sangamonian section and an early Wisconsinan section, but both ar e missing the late Wisconsinan. The ages for the following pollen zone s are estimated by correlation with the deep-sea delta(18)O record. In the late Illinoian, Picea-Pinus pollen zone 1, dating from about 150- 130 ka, represents an apparently closed boreal coniferous forest indic ating a cold late-glacial climate. The Sangamonian includes three majo r pollen zones ranging from about 130-75 ka. The early Sangamonian is represented by Quercus-Ulmus-Carya-Fagus dominance in zone 2, indicati ng vegetation comparable to the modern deciduous forest and climate th at was warm and moist. The middle Sangamonian in zone 3, which is char acterized by Ambrosia-Poaceae-Cupressaceae-Quercus pollen, suggests a savanna vegetation and a warm, dry climate. The late Sangamonian is su bdivided into a Quercus-Ulmus-Carya subzone (4a) that indicates a mesi c forest and greater precipitation; a Quercus-Ambrosia subzone (4b) th at suggests drier climate and savanna conditions; and a Quercus-liquid ambar-Carya subzone (4c), containing the 'southeastern forest' element , Liquidambar, suggesting the peak in warmth and moisture. The early W isconsinan is represented by a transitional Picea-Chenopodiineae zone (5). This unusual assemblage suggests a cool prairie-like vegetation, perhaps with scattered Picea trees at the end of that depositional int erval. The Middle Wisconsinan is marked by the return of high percenta ges of Picea and Pinus pollen in zone 6. The latest pollen zone (7) is dominated by Chenopodiineae pollen and is absent at Raymond Basin. It is most likely Holocene in age, and probably represents prairie condi tions and warm, dry climate. Apparent surface-temperature and apparent effective-moisture curves were derived from the first detrended corre spondence analysis (DCA) axis of the pollen data. The first axis corre lates well with the normalized deep-sea delta(18)O curve of sea surfac e temperature, and the second is controlled mainly by precipitation. T he interglacial vegetation differs from that predicted by models drive n by orbitally-induced insolation curves.