THE WESTERLO ICE STREAM: A NEWLY IDENTIFIED LANDSYSTEM IN EASTERN NEW YORK STATE

In eastern New York State, near Albany, the Mohawk Lobe and Hudson Lobe of the Laurentide Ice Sheet (LIS) have traditionally been mapped as divergent ice streams demarcated by well-defined drumlin fields that flow parallel to the major stream valleys. However, new lidar elevation terrain models now reveal a series of separate and distinct landforms associated with a previously unidentified ice stream flowing southwestward for a distance of 80 kilometers.

We designate this newly recognized ice stream based on a well-developed drumlin field centered near the hamlet of Westerlo. The undulatory flow path extends from the Hudson Valley over the Helderberg Escarpment and northeastern escarpment of the Catskill Mountains composed of Devonian sedimentary rocks. Unlike the Mohawk or Hudson flowlines, the Westerlo flowline climbs more than 500 meters in elevation before crossing the drainage divide and descending into the Schoharie Basin. We interpret the unusual flow path of the Westerlo Ice Stream to represent development during a period of major ice strengthening of the LIS in eastern New York.

New geologic mapping and fieldwork sponsored by the Great Lakes Geological Mapping Coalition has resulted in development of a landsystem model that defines proglacial, ice-marginal and subglacial zones and corresponding sediment-landform associations. Supporting stratigraphic and chronologic investigations are ongoing in efforts to better understand time and distance relationships of landform development along the flow path of the Westerlo Ice Stream.

Fine-grained sediments such as glaciolacustrine clays and tills are susceptible to rotational and translational slope failures. Such failures may pose challenges to construction and may adversely impact water resources. New geologic maps and a better understanding of glacial landsystems will provide essential geologic data to help manage land-use and mitigate geologic hazards.