3D MODELING OF SURFICIAL SEDIMENTS IN THE STONY CLOVE BASIN, CATSKILL MOUNTAIN REGION OF NEW YORK

The Stony Clove watershed is part of the Esopus drainage basin, which feeds into the Ashokan Reservoir, a source of New York City drinking water. Glacial sediment- specifically clay-rich till and glacial lacustrine rhythmites- contributes to the major turbidity problem within the watershed. Mapping surficial sediments along stream beds allows identification of sites where turbidity originates.

As part of the SUNY New Paltz REU program, we extensively mapped post-Hurricane Irene surficial sediment exposures in the basin and significantly increased our understanding of the stratigraphy from previous years’ mapping efforts. Previous studies identified glacial lacustrine sediments stratigraphically below a red clay-rich till. We now recognize two separate lacustrine units and both are overlain by till. The lower lacustrine unit is clay-rich rhythmites. A basal diamicton facies in the lower red till contains deformed rhythmites with pebbles. When exposed, the contact with underlying lacustrines shows deformation consistent with ice override. The second or upper lacustrine unit represents a shallower water package often composed of deformed and faulted sand and silt. This upper lacustrine unit is truncated by a second red till with occasional deformed erratic blocks of the underlying lacustrine rhythmites. On the valley floor, glacial sediments are truncated by alluvial terraces.

A 3D model of the basin fill was generated from our map plus well log data using ArcMap and ArcScene. Three meter resolution LiDAR was used to determine geomorphic features along the valley walls between field transects. Well logs were compared to field data collected in close proximity to the wells to better comprehend the stratigraphy not revealed in the field. Using the Xacto tool in ArcMap, a 2D cross-section along streams was developed to visually display this stratigraphy. The model estimates as much as 92 meters of sediment in the valley floor of the Stony Clove Basin. This sediment is comprised of a significant amount of silt and clay which will continue to contribute to the runoff turbidity in the future.