Clarion Clay, Jackson Co., Ohio, USA

Age: Pennsylvanian (298.9 - 323.2 Ma)

Stratigraphic Name: Allegheny Group; Pottsville Group

Description: Shale, siltstone, and underclay: Shale, black, gray, and olive; clayey to silty; locally contains marine fossils; calcareous in part. Siltstone, gray, greenish and olive; clayey to sandy; thin bedded to medium bedded; locally contain marine fossils. Underclay, gray and olive; generally 3 feet or less in thickness; clayey to silty; commonly rooted and underlying coal beds; nonbedded; locally varies from flint to plastic clay. Sandstone, light to medium gray weathers to shades of yellow-brown; mostly very fine to medium grained, locally quartzose and conglomeratic in lower one-third of unit; thin to massive to cross bedded; locally calcareous; Limestone, flint and coal. Limestone, black to light gray; micritic to medium grained; locally grades into flint; thin to medium bedded to discoidal concretions containing marine fossils; locally nonmarine, micritic limestones occur beneath coal beds in upper one third of unit. Coal, mostly banded bituminous, locally cannel; thin to locally as much as 12 feet thick; generally in discrete beds but locally contain shale partings and split into multiple beds. Lateral and vertical lithic variability and gradation common. Unit as much as 700 feet thick.

Comments: Secondary unit description from USGS Lexicon website (ref. OH017) and OH003:Core drilling in poorly exposed Lower and Middle Pennsylvanian strata of Pottsville and Allegheny Groups in northeastern OH has led to better understanding of key Pennsylvanian marine units and has identified previously unknown marine and marine-influenced strata in lower part of Pottsville Group. Geologic column for Lower and Middle Pennsylvanian rocks of Bownocker and Dean (1929) needs revision. Currently, Ohio Geological Survey considers all stratigraphic terms below "group" status as informal. In addition, some named units such as most coal beds and sandstone beds cannot be correlated from northeastern to central and southern parts of OH. Three marine units are widely traceable in Pottsville of northeastern OH (ascending): Lowellville, Lower Mercer, and Upper Mercer limestones; a fourth, Boggs limestone and ore, is recognized mainly in central OH. Drilling identified two other units, designated unit A and unit B for this report. The revised column for the Pottsville Group in northeastern OH is (ascending): Sharon coal, marine unit A, Lowellville marine unit, Quakertown coal, marine unit B, Lower Mercer coal zone, Lower Mercer marine unit, Upper Mercer coal zone, and Upper Mercer marine unit. Authors suggest that well-defined local names be applied to these stratigraphic units rather than names projected from other parts of Appalachian basin (Slucher and Rice, 1994).

Lithology: Major:{shale,siltstone}, Minor:{limestone,sandstone}, Incidental:{claystone, bituminous}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]