A LATE QUATERNARY SEDIMENT, POLLEN, AND CHARCOAL RECORD FROM BALLSTON LAKE, NY

Pollen, charcoal, and sediment records developed from two cores provide the first continuous records of sediment influx, vegetation, and fire during the late Quaternary from Ballston Lake, New York. Pebbles at the base of both cores and the geomorphology of the lake document the northward flow of the paleo-Mohawk River through the Ballston Lake basin prior to ~12,497+100 cal. yr. B.P. (11,000+55 14C yr. B.P.). The transition from fluvial to lacustrine sediment in this avulsed channel indicate that Ballston Lake formed 11,000±55 14C yr B.P., during the onset of the Younger Dryas (YD). The avulsion of the Ballston channel may have been caused by the rapid drainage of Glacial Lake Agassiz through the St. Lawrence and Mohawk Valleys. Bulk density, magnetic susceptibility (MS) and organic carbon reflect warming at ~10,094+200 cal yr B.P. MS measurements reveal that the influx of dense, magnetic particles, which are associated with deglaciation, ceased after ~9160+55 cal yr B.P. The transition from clays to gyttja with low MS, low bulk density, and high organic carbon in both cores may indicate increasing productivity and a warming trend from ~10,094+200 cal yr B.P. into the early Holocene. Fire frequency was high during the YD, low during much of the early Holocene and moderate throughout the late Holocene. The pollen record defines 5 distinct zones: (1) Boreal forest-12,917 to 11,755 cal yr B.P., (2) Transitional forest-11,755 to 10,008 cal yr B.P., (3) Tsuga-dominated hardwood-10,008 to 3,490 cal yr B.P., (4) Mixed hardwood-3779 to 2,393 cal yr B.P., and (5) Coniferous-2,393 cal yr B.P. to present. The pollen and sediment record are consistent and indicate stabilization of the landscape and warming throughout Zone 1, continued warming through Zone 4, and cooling leading into Zone 5. The decline in Tsuga canadensis at the end of Zones 3 most likely reflects preferential selection by a parasite, rather than climate change.