A POLLEN RECORD OF THE YOUNGER DRYAS FROM THE SEDIMENTS OF SILVER LAKE, SUMMIT COUNTY, OHIO

Pollen records from lacustrine sediments can provide a better understanding of past vegetation and climatic conditions. Following the deglaciation of the Laurentide Ice Sheet, the kettle lake, Silver Lake in Summit County, Ohio formed. A complete sediment record from Silver Lake was recovered in a 13.5-meter-long core. Prior work revealed the first increase in organic matter occurs at 1069 cm deep in the core. This initial rise in organic matter was selected for pollen study. Pollen was isolated from twenty-one subsamples using standard chemical acetolysis methods. Pollen grains were identified and counted under a 400x magnification light microscope. Organic-poor sediment (8-11%) samples from below 1069 cm contains high Picea (18-33%), Abies (9-23%), and low Pinus (2-4%) concentrations. At 1069 cm depth, there is a pronounced change in organic matter content and pollen taxa. Above 1069 cm, the organic-rich sediment (13-34%) contains low Picea (2-12%), Abies (2-18%), and high Pinus (34-65%) concentrations. Picea and Abies indicate cold, moist conditions, whereas Pinus indicates cool, dry conditions with open area. Published pollen studies have shown the shift from predominantly Picea and Abies to Pinus to be an identifying characteristic of the Younger Dryas onset in the Allegheny Plateau region of Ohio. The inferred onset of the Younger Dryas in the Silver Lake sediment record correlates to published, well-dated pollen records from Ohio. The relative dating correlation has allowed the chronology of Silver Lake to be better constrained. Furthermore, the Silver Lake pollen record provides a better understanding of past vegetation, giving evidence of past climate conditions.