Named the Tumbling Run member of the Pottsville formation in eastern PA. Predominantly conglomerate and sandstone with less quantities of conglomeratic sandstone, siltstone, shale, and coal; conglomerate beds are coarser and less well sorted in lower part of member and proportion of sandstone, conglomeratic sandstone, siltstone, shale, and coal beds somewhat greater in upper part. Comprises basal 535 feet of formation at reference section. Conformably overlies Mauch Chunk formation (contact arbitrarily placed at top of uppermost sandstone, siltstone, or shale) and underlies Schuylkill member of Pottsville. Lower contact is considered by many to be the Mississippian-Pennsylvanian boundary. Regional studies indicate that there may be considerable intertonguing of facies between the Tumbling Run member of the Pottsville and the Mauch Chunk formation. Therefore it is possible that the time boundary, as recognized in type and reference sections, is in rocks of the Mauch Chunk formation at some localities and in rocks of the Pottsville in other places. The Tumbling Run is of Early Pennsylvanian age.

Source: GNU records (USGS DDS-6; Reston GNULEX).

Revised the Tumbling Run as the Tumbling Run formation of the Pottsville group in eastern Pennsylvania.

Source: GNU records (USGS DDS-6; Reston GNULEX).