PALEOZOIC STRESS ORIENTATION IN THE SOUTHEAST OZARKS

The Late Paleozoic North American Craton shows a transition from the Ouachita–Appalachian Orogeny far-field deformation to a mid-continent NE-SW shortening trend. The location of this transition can provide information as to the stresses associated with the formation of Pangea. A unique opportunity to evaluate this stress orientation arose when, in 2005, a 2.5 km long section of the Lower Ordovician Cotter Dolomite was exposed during the construction of a highway bypass near the town of Hardy, AR. Structural features exposed include five reverse faults, 19 fault-related folds, and 17 joint zones. These features generally strike N-NE, and indicate NW-SE crustal shortening. Stereonet solutions suggest that this major NW-SE compression reactivated features having a NE-SW strike that had formed during a pre-existing tensional stress regime. The data are consistent with compression related to the Ouachita–Appalachian Orogeny. The NW-SE compression due to this event extends further north than previously recognized.