GETTING TO THE BOTTOM OF IT: HOLOCENE CLIMATE CHANGE IN KEUKA LAKE BASED ON SEDIMENT CORES

Deep lakes such as Keuka Lake, located in the Finger Lakes region of New York, permit continuous and undisturbed sedimentation since the last deglaciation. Analysis of this continuous record from the southern end of the lake allows us to determine the paleoenvironmental and paleoclimate changes that occurred during the Holocene. In this study, we recovered a ~4 meter piston core from the deepest part of the lake that encompassed sediment deposition from the entire Holocene. We analyzed for magnetic susceptibility, sediment grain size, charcoal content, water content, organic content and carbonate content. The majority of the core, from 0-336 cm, is represented by poorly laminated to highly mottled sediment and the lower section, from 336-379 cm, displays distinct laminations. Preliminary grain size data reveals a fining upward sequence over the past 14,000 years. Superimposed on this are six events that each result in a brief but dramatic fining of the sediments, possibly caused by decreased storm intensity. Conversely, six brief but dramatic periods of increased mean grain size were also recorded, possibly caused by increased storm intensity. There is a moderate correlation between mean grain size and magnetic susceptibility, where magnetic susceptibility increases with increased grain size. Based on an observed increase in charcoal abundance from 347 cm to 358 cm in depth, forest fire frequency is believed to have increased from background levels and is associated with an increase in grain size. Analysis in progress will determine more precisely relative abundance of charcoal in the Keuka Lake watershed and will be compared to grain size to infer relative wetness of past climates.