An Obstructed Cave Passage in the Cobleskill Plateau: A Gravimetric Study

Abstract

The Cobleskill Plateau of central New York, part of the greater Helderberg Plateau, is comprised of Silurian and Devonian limestone. This area displays caves and karst landforms subsequently altered by glaciation. The glacially mantled and in-filled pre-existing karst topography of the area was caused by hydrologic changes that determined current karst flow paths. Determining the nature of the antecedent topography, and the location of cave passages, is critical to a complete hydrologic analysis of the Cobleskill Plateau. Two gravity traverses were conducted along traverses near Cobleskill, New York using a Worden Gravity Meter with the intent to validate the subsurface location of an occluded abandoned trunk passage connecting Howe Caverns and McFails Cave. To clarify, the term ‘abandoned’ is meant as an identifier that the passage is no longer utilized as the primary flow path and is only utilized by flowing water during periods of moderate to high discharge. The importance of the existence or absence of the abandoned trunk passage is to increase the understanding of subsurface geology, potential hazards, and controls on pre-glacial groundwater flow in the region. The findings of this study conclude that subsurface anomaly sources do exist at anticipated locations which were believed to contain the passage in question. The study demonstrates that it is possible to identify this passage through the use of gravity surveys. However, the exact shape and size of the anomaly cannot be definitively determined by this study, as the true depth to bedrock could not be determined. Though it is possible to roughly estimate passage dimensions based on a knowledge of the traversable, upstream and downstream passages. The data collected in this study can be fit to various models which can be interpreted to support the existence of a void beneath the two traverses. Further exploration of the subsurface karst systems in the region is needed to determine the exact nature of the anomaly sources.