Black shale over quartzose sandstone in the Paleozoic of Ohio, USA.

This outcrop in southern Ohio exposes the Sunbury Shale-Berea Sandstone contact. The Sunbury Shale is a black mudshale succession - it is the oldest fully Mississippian-aged unit in the state. It occurs above the Berea Sandstone and below the Cuyahoga Formation. The Sunbury essentially identical to the older Ohio Shale. Compared with the Ohio Shale, the Sunbury is considerably thinner. Sunbury outcrops are uncommon, but an extensive exposure is present at the Tener Mountain roadcut in southern Ohio. The unweathered rocks are black mudshales, but weathered material consists of medium- to light-colored chips. I have not observed fossils in the Sunbury at this site, but the literature refers to lingulid brachiopod fragments in the lower Sunbury.

The light-colored rocks in the lower part of the photo are the uppermost Berea Sandstone. This unit caps a coarsening-upward succession that starts with the Olentangy Shale, followed by the Ohio Shale, the Bedford Shale, and the Berea Sandstone. The Ohio Shale and Bedford Shale are Famennian in age (= upper Upper Devonian). Traditionally, the Bedford and the Berea have been considered as Lower Mississippian. The Berea is now known to be Famennian (~latest Devonian), based on palynomorph microfossils. The Devonian-Mississippian boundary may lie within the Berea Sandstone. A Kinderhookian-aged conulariid has been found in the basal part of the overlying Sunbury Shale.

Stratigraphy: Sunbury Shale, Kinderhookian Stage, lower Lower Mississippian

over

Berea Sandstone, upper Famennian Stage to lower Kinderhookian Stage (?), upper Upper Devonian to lower Lower Mississippian (?)