Silurian rocks of northern Arkansas
From Batesville, Arkansas, in Independence County, follow Arkansas 69 north to Cushman (Fig. 1). Turn left (west) on the county road (paved) just beyond the Cushman General Store. If you consider this intersection the zero point of a road log, the pavement ends at about mile 3.5 (5.6 km). At mi 5.1 (8.2 km) you will drive past a good outcrop of Ordovician age limestones of the Plattin, Kimmswick, and Fernvale formations. Of particular interest here is the Plattin-Kimmswick contact, which is sharp and “welded” as well as angular. The Plattin occurs in a small synclinal fold that is truncated by the basal sandy Kimmswick. An orange-colored zone several yards up the road marks a fault that lowers the Fernvale to a position adjacent to the Kimmswick at road level. (See W. W. Craig’s discussion of the lithologies of these units elsewhere in this volume.) At mi 7.0 (11.3 km) is the entrance to Love Hollow Quarry (Fig. 2). The outcrop described below can be found approximately 0.2 mi (0.3 km) north of Love Hollow.
The exposure consists of approximately 60 ft (18 m) of Brassfield, St. Clair, and Lafferty limestones. The shale on which the Brassfield rests at this locality is probably Ordovician age. The lithologic sequence consists of 4 ft (1.2 m) of spar-cemented, coarse fossil debris, overlain by 4 ft ( 1.2 m) of St. Clair, which in this locality is represented by a biomicrite. The contact at this point is slightly angular. The St. Clair is
Figures & Tables
One of six volumes generated by each GSA section for the Decade of North American Geology (DNAG) project, this Centennial Field Guide contains descriptions of 100 sites or site clusters representing outstanding geologic locations in Arkansas, Kansas, Oklahoma, and Texas.