6 Applied Geological Investigations at State Geological Surveys in the Northeastern Section of GSA (Posters)

This technical session will highlight the high-level, applied work done by state geological surveys to address diverse environmental issues including geologic hazards, groundwater and surface water, and economic mineral deposits in the Northeast Section region.

Sunday, 22 March 2026
8:00 AM - 12:00 PM
CCC, Ballroom C

Identifying Karst Closed Depressions in a Glacially Mantled Terrain

Paper number: 6-0
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Mapping karst closed depressions for geohazard assessment encounters challenges in terrains mantled by glacial deposits and altered by periglacial processes. Karst closed depressions and sinkholes can resemble glacial and periglacial features such as kettles, pingos, and deflation hollows when examined on lidar-derived images. Some field observations and desktop (remote) techniques can help to parse the karst depressions from those of glacial origin.

Northampton County, Pennsylvania, located in the Great Valley by the Delaware River, has experienced at least two glacial advances. The Pre-Illinoisan-G (MIS 22, >788 Ka) deposits extend across the entire county, and till thickness ranges from zero to 5 m. The Wisconsinan (MIS6, ~20 Ka) glacier covered the northeastern portion of the county depositing till 2 to 40 m thick. The region also has experienced multiple episodes of periglacial landscape alteration.

Closed depressions were identified as definitively karst if bedrock was observed within them or in nearby outcrop. Evidence of water actively entering the closed depression led to the assumption of karst origin. Active karst features tended to have a more circular parapet and steeper sides. Depressions were interpreted to be glacial or periglacial by several characteristics. In the field, one contained a pavement of interlocking outwash cobbles overlain by fine sediments, interpreted to be a deflation hollow. If the depressions were within the terminal moraine, or were proximal to a sand and gravel quarry that was deeper than the depression, they were assumed to be glacial in origin. Several were noted to have a raised rim, possibly former pingoes, or a “wormy” texture around them, likely solifluction lobes. Very broad (>10s m) and shallow (<1m) features were discounted as relic glacial features unless they had active sinkholes within them. The landscape of Northampton County has been further complicated by 30 m of let down due to carbonate dissolution since the oldest glacial retreat. This poster hopes to explain which depressions are definitively karst, which are interpreted as glacial, and invite discussion on how to resolve the remaining ambiguous features.

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

doi: 10.1130/abs/2026NE-411133

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