6. Caves and Karst of the Deformed Siluro-Devonian Carbonates, South Central New York

The Siluro-Devonian Helderberg Group carbonates and the mid-Devonian Onondaga Limestone of the Hudson River Valley were highly deformed by the Acadian Orogeny, which limited subsequent outcrop extent and catchment. Glaciation overprinted the tectonic structure and obliterated, modified, and engendered cave development. Ice movement was north to south, parallel to the structural grain and the adjacent Hudson River, and differentiating the controls of cave development is difficult. Clarksville Cave and Onesquethaw Cave appear pre- and post-glacial, respectively, despite similar sizes in excess of 1 km (0.63 miles), and both show significant structural control. Farther south, the Joralemon Park caves display maze development initiated post-glacially, adjacent to pre-glacial cave remnants in a deranged drainage setting. Pompeys Cave is developed in a limestone member of the Rondout Formation, a member not present west and north in the main Helderberg Plateau. The cave is a single stream-capture passage of large size with a backflood maze overprint upstream of a major collapse area; despite the large size, the cave otherwise fits the criteria of being post-glacial in origin. Mystery (Surprise) Cave at 3 km (2 miles) is the longest cave in this region, and sits near the southern glacial boundary and appears pre-glacial in origin. Numerous other small caves are strewn along the Hudson River Valley, and all show an interesting interplay between structure, lithology and glaciation.