STRUCTURAL CONTROLS ON SANDSTONE CAVES IN NORTHEAST OHIO
Virginia Kendall Ledges yielded 93 total joints, which were divided into two major joint sets: one representing the cliff faces and vertical joints parallel to the valley walls (J1) and the other containing all joints approximately normal to J1 that penetrate into the sandstone knobs (J2). 31% of the total joints are J1 having a mean strike of 358°, 55% are J2 having a mean strike of 076°. Camp Christopher yielded 45 total joints, also divided into joints sets J1 and J2. 47% of the total joints are J1 having a mean strike of 340°, 36% are J2 having a mean strike of 038°. Little Mountain yielded 120 total joints that were divided into cliff faces (J1) and normal cross-joints (J2), but the orientations of the strikes show no clustering or preferred orientations.
Joint sets were compared to joint orientations from previous work. J2 joints found at Virginia Kendall Ledges possibly correlate to the shallow Ohio joint set CFJV4 from Evans (1994) or a set described in Ohio sandstone by Ver Steeg (1944), both which parallel the ENE maximum horizontal compressive stress of the contemporary stress field. The J2 joints of Camp Christopher may also be correlated to Ver Steeg’s sandstone joint set. It is probable that the J1 joint sets from all locations were formed from topographic stresses rather than the regional tectonic stress field. This is supported by 2D models that show the greatest stresses at valley margins, parallel to cliff faces. Stresses along valley margins would be intensified by the retreat of the Pleistocene glacier, potentially resulting in neotectonic unloading joints.