CLIMATE AND HUMAN SETTLEMENT RECORDS IN SILVER LAKE, OHIO

Paleolimnological analyses of siliceous microfossils are used to reconstruct conditions in Silver Lake, west-central Ohio over the past 14,000 years as they relate to climate and European settlement. Previous paleomagnetic (Yifur 2002) and pollen studies (Odgen 1966) revealed that the Silver Lake record contains both climate and human disturbance signals. A 10 m sediment record obtained from Dr. John Peck, University of Akron, was sub-sampled and analyzed for microfossils (diatoms, chrysophytes and carbon particles). Unconstrained correspondence analysis was used to summarize major variation in diatom community structure for the past 13,350 years. Variations in diatom composition show a human disturbance signal and distinct shifts in Holocene climate from glacial to interglacial conditions in the Silver Lake watershed. Early Holocene diatom flora are dominated by benthic pioneer species. Diatom assemblage shifts in older sediments are primarily climate driven. Evidence of the Younger Dryas cold period (12.2 to 13.4 cal. yr BP) is indicated by a peak in Cyclotella ocellata, a cold-water species. Beyond the known Holocene climatic transitions (10.0- 0.3 cal yr BP), evidence of seven short-term cold climatic oscillations occur between 8.2 cal. yr BP and 0.3-0.86 cal. yr BP. These are recorded as abrupt increases in the cyst to diatom ratio, indicative of cold environmental conditions. Increases in benthic species, cyst to diatom and carbon particle to diatom ratios suggest cold and dry conditions, while increases of planktonic species suggest moist conditions. This research provides further insight into the climatic conditions in Ohio and the southern Great Lakes region during the Holocene.