Hi, Bill,
There is indeed a master cave system under the Cobleskill Plateau. It was the subject of a paper by Hydrogeologist and NSS Member John Mylroie and Jeremy Weremeichik back in 1977. Here's a link to a map of the sunken system, or "buried valley": https://www.researchgate.net/figure/A-Map-of-the-karst-systems-and-flow-routes-of-the-Cobleskill-Plateau-The-buried-valley_fig2_268148983
Fascinating area, with lots of caves, many hydrologically connected, as you can see.
Peter Youngbaer
NSS 16161 CM FE