File:Coal raft & fossil log in sandstone (Sharon Sandstone, Lower Pennsylvanian; Irish Ridge East roadcut, near Trinway, Ohio, USA) 5 (33062231662).jpg

Coal raft & fossil log in sandstone in the Pennsylvanian of Ohio, USA. (geology hammer for scale)

The Pottsville Group is 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 here is a talus block of quartzose sandstone from the Sharon Sandstone, a basal to near-basal member of the Pottsville Group. The Sharon varies from sandstone to pebbly sandstone to conglomeratic sandstone to conglomerate. Clasts are usually rounded quartz pebbles. Some limestone clasts derived from the Maxville Limestone are occasionally present. Body fossils, if present at all, are usually logs. The Sharon usually occurs immediately above the Mississippian-Pennsylvanian unconformity, which is a megasequence boundary in Ohio.

The yellowish brown coloration is from iron oxides. The elongated, striated structure near the center is a fossil log. The black structure just below the middle is a coal raft. It originated as a floating mat fragment of peat in an ancient river. After burial in sand, the peat was compacted and altered into coal.

Stratigraphy: Sharon Member (Sharon Sandstone), lower Pottsville Group, upper Lower Pennsylvanian