35-6 Interpretations of the Geomorphology of the Eastern Tug Hill Plateau and Southern Black River Valley Regions, New York State

Session: Ice sheets, glaciers, and landscapes, oh my! (Posters)

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Abstract:

Beginning in 2023, the New York State Geological Survey began a federally funded stratigraphic and surficial materials investigation of the 32 quadrangles of Lewis and adjacent counties in the Black River and Tug Hill Plateau Regions of New York. Mapping is sponsored by the National Cooperative Geologic Mapping Program-STATEMAP and the Great Lakes Geological Mapping Coalition programs of the USGS. Prior mapping in the early 20^th century (Fairchild, 1912) was completed at a more regional scale and observed the existence of glaciolacustrine, ice-proximal and outwash deposits in the region. Current work encompassing over 1,150 sampling stations, 330 soil textural analyses and 20 traverses conducted within the first four quadrangles mapped evidences multiple episodes of glaciation and the existence of additional smaller, temporal glacial lakes.

Lewis County, located in northwestern New York, lies on the western edge of the Precambrian-aged Adirondack Lowlands and contains most of the Ordovician-aged Tug Hill Plateau. The Tug Hill Plateau, a distinct province of very shallowly-dipping and fractured sedimentary rock, overlies the extensively deformed metamorphic rock of the Adirondack Lowlands. Rocks of either age are juxtaposed along a contact that runs nearly parallel to NYS Route 12. These rocks are extensively weathered by glacial processes and while some form outcrops, others are covered by over 300 feet of glacially derived sediment. The Black River Valley creates a distinct trough through Lewis County with glacial lake spillways at its southern end at various elevations.

In the century since Fairchild first published the results of his study (NY State Museum Bulletin 160), new interpretations of the events that shaped the glacial features of the Black River Valley were made by applying similar techniques for high-resolution mapping combined with new technology. Within southern and eastern Lewis County, field mapping indicates the existence of multiple glacial lake elevations and palimpsest geomorphic features that coincide with both surface and subsurface stratigraphic layers. Geomorphic landforms expressed at the surface are composed of a variety of sediments both proximal and distal to the ice front. Taken together, this variety in sediment source, stratigraphy and geomorphology allow for the interpretation of past glacial events at the local scale with regional implications. Further mapping and geochronology results will further solidify our understanding of the temporal relation between these events.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

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