CONTROLS ON JOINT FORMATION DURING GLACIAL UNLOADING OF THE SHARON SANDSTONE AT GORGE METRO PARK, AKRON, OHIO

Exposures of the Sharon sandstone at Gorge Metro Park in Akron, Ohio, contain many continuous and discontinuous joints in similar orientations. The Sharon sandstone is a nearly pure quartz sandstone with medium grain size formed during the early Pennsylvanian period. Joints in these exposures of the Sharon Sandstone formed during glacial unloading following the last glacial maximum. Preliminary results indicate that there are two major joint sets made up of both continuous and discontinuous joints. The first joint set (J1) makes up the face of the outcrop having a SE orientation. The second joint set (J2) has a NE orientation and is normal to (J1). Discontinuous joint sets were less than four meters in length and terminated for a variety of reasons: 7% of discontinuous joints terminated because of preexisting joints, 22% terminated because of changes in lithology, and 71% terminated randomly within the rock. Continuous joints were greater than four meters long and terminated at the end of the outcrop. These results indicate that stress relaxation effects the propagation of joints more than interference with other interfaces such as preexisting joints and changes in lithology.