T108 Geologic Maps, Digital Geologic Maps, and Derivatives from Geologic and Geophysical Maps (Posters)

Monday, 1 November 2010
8:00 AM - 6:00 PM
Hall D

THREE-DIMENSIONAL SURFICIAL GEOLOGIC MAPPING, SHANDAKEN QUADRANGLE, CATSKILL MOUNTAINS, NEW YORK

Paper number: T108-19
Program: Technical Sessions
Time: 8:00 AM – 6:00 PM

Authors

Abstract

Drainage basins in the Catskill Mountains of southeastern New York State provide the majority of drinking water to the residents of New York City. One such catchment is that of Esopus Creek which is the main tributary to Ashokan Reservoir. Recently, unacceptably high turbidity levels have been intermittently recorded in the reservoir spurring geologic investigation into the source(s) of fine-grained suspended sediments responsible for the turbidity.

Surficial geologic mapping of the Shandaken Quadrangle in the upper reaches of Esopus Valley largely reveals till, deposited during the late Pleistocene glaciation, and alluvium and colluvium deposited during the Holocene. Evidence of lacustrine silt and clay, deposited in pro-glacial lakes dammed in the valley during deglaciation, are exposed only in limited exposures along Esopus Creek and its tributaries. Thus, in order to determine the lateral extent and thickness of fine-grained sediments three-dimensional mapping was required. A drilling campaign was undertaken in Esopus Valley including five holes distributed over 3 quadrangles. Preliminary results indicate extensive lacustrine deposits to thicknesses of 25 m and a variety of glacial stratigraphies that can be used to determine the deglacial history of the region.