Abstract

The Silurian and Devonian rocks of northern Arkansas are widespread in the subsurface reaching an aggregate thickness of over 480 feet in Pope County. This thickening may continue southward into the Ouachita region.

The surface exposures are generally restricted to the Springfield Plateau physiographic province where outcrop thicknesses are quite variable due to contemporaneous, and post-depositional erosion. No single formation is well-developed on the outcrop across the entire area, although the Chattanooga Shale is rather extensive in the northwestern, and the St. Clair Limestone in the northeastern, portions of the region.

The regional structural strike of the Silurian and Devonian formations in northern Arkansas is generally east-west, and the dip is to the south. The angle of dip is slight in the Ozark region and becomes increasingly steeper to the south into and across the Arkansas Valley where it becomes mantled by a thick wedge of Pennsylvanian and Mississippian sediments.