FRACTURING ON THE ONONDAGA ESCARPMENT, LEROY NY

This research evaluates fracturing at the Onondaga escarpment in an area that contains numerous fracture traces and depressional features that have been interpreted to be sinkholes. The study is located in western NY in an area that has suffered several groundwater contamination events. Fracture orientation and spacing was measured in order to subdivide the strata into hydrostratigraphically meaningful intervals. Fracture characteristics such as weathering and the presence or absence of travertine deposits were also noted. The goal was to identify the most important groundwater flow zones in the escarpment. Fracture data was grouped by the following units: Camillus Shale, Akron Bertie group, Basal Edgecliff, Moorehouse and Nedrow. The results suggest that there are two populations of fractures which are oriented 300 and approximately 35 degrees (20 – 50). Local fracture traces trend northeast, which is subparallel to the 35 degree fracture population. It was determined that two circular features in Oatka Creek which were once interpreted as sinkholes, are not sinkholes, but are in fact areas where fracture spacing is much thinner. The closely spaced fractures were more easily plucked away by the stream flow, creating circular gouges in the stream bed. The results show that there are local areas of enhanced fracturing which may be partly responsible for fracture traces and other "sinkholes" -like features. The location and orientation of these zones of enhanced fracturing are important because they probably control the movement of groundwater in the study area.