CAVE-HOSTED GLACIOLACUSTRINE FACIES AS INDICATORS OF THE FOOTPRINT OF GLACIAL LAKE SCHOHARIE, HELDERBERG PLATEAU, CENTRAL NEW YORK

Glaciolacustrine lithofacies deposited during the Wisconsin glaciation were found in eight pre-glacial caves inundated by Glacial Lake Schoharie located in the Helderberg Plateau region of Schoharie County in central New York. The lithofacies consisted of three individual facies, referred to collectively as a ‘sediment package’, which are stratigraphically uniform with the middle facies in sharp contact with the facies directly above and below. The packages found in the eight caves all displayed a similar stratigraphic sequence, from bottom to top: tan/white and or light grey, very thinly bedded, silts and clays overlain by poorly sorted, matrix-supported gravels overlain by dark brown very thinly bedded silts and clays. Laboratory analyses of 63 sediment samples from all eight caves displayed varying weight percents of the organic content of each sample. However, the analyses indicated a higher concentration of fine-grained calcite material in the tan/white and light grey facies than in the overlying facies. Caves located at lower elevations contain a thicker tan/white and light grey sediment section than those caves found at higher elevations. This relationship is thought to be a measure of the duration of glacial lake water inundation, the lower elevation caves being inundated the longest. A post-glacial cave within the lake footprint, and a nearby pre-glacial cave outside the lake footprint, lack the glaciolacustrine lithofacies. The tan/white and light grey sediment facies represents glacial rock flower deposited under stagnant lake conditions that limited fine-grained calcite particle dissolution. The overlying gravel facies were emplaced during lake termination and reestablishment of epigenic flow in the eight stream caves. The more recent dark brown facies resulted from soil-loss deposition following European settlement. These results explain why the unusual tan/white and light grey facies are not found in other caves within the same lithologies in the central New York region, as these areas were not subject to inundation by glacial lake water.