Coiled cephalopod in the Pennsylvanian of Ohio, USA. (geology hammer for scale)

"Lowellville Shale" is the nickname used here for dark-colored mudshales overlying the Lowellville Limestone in the Pottsville Group of northeastern Ohio, USA.

Just above the Lowellville Limestone at the Beach City Dam outcrop, the Lowellville Shale is fissile to flaggy, fossiliferous, black calcareous shale. Above that is non-flaggy, sparsely-fossiliferous, incompetent, black calcareous shale. Observed fossils include Posidonia bivalves, Trepospira gastropods, crinoid stem columnals, straight-shelled nautiloid cephalopods, coiled cephalopods, plants, and horizontal burrows.

The Lowellville Shale and underlying Lowellville Limestone are part of the Pottsville Group, a Pennsylvanian-aged cyclothemic succession in eastern Ohio that contains nonmarine shales, marine shales, siltstones, sandstones, coals, marine limestones, and chert ("flint"). The lower Pottsville dates to the late Early Pennsylvanian. The upper part dates to the early Middle Pennsylvanian. The Lower-Middle Pennsylvanian boundary is apparently somewhere near the Boggs Member (?).

Shown above is a mold of an unidentified coiled cephalopod shell in dark mudshale. It is either a coiled nautiloid or an ammonoid. This type of creature is basically a squid-in-a-shell, similar to the modern chambered nautilus (www.flickr.com/photos/jsjgeology/21726189464).

Classification: Animalia, Mollusca, Cephalopoda, Nautiloidea or Ammonoidea

Stratigraphy: Lowellville Shale, just above the Lowellville Limestone, Pottsville Group, upper Lower Pennsylvanian