Monongahela series is divided into 12 named cyclothems. The Arnoldsburg is composed of the strata between the Benwood cyclothem below and the Lower Uniontown cyclothem above. Includes (ascending) Fulton shale and sandstone, Arnoldsburg redbed, Arnoldsburg limestone, Arnoldsburg underclay, Arnoldsburg coal, and Arnoldsburg roof shale members. [Arnoldsburg sandstone is included in the Lower Uniontown cyclothem.] In its normal position between Benwood coal bed and Arnoldsburg sandstone, average thickness of cyclothem in Athens Co. is a little over 16 ft. Individual members do not regularly appear in section, and their thickness frequently exceeds average thickness of entire cyclothem. Where Benwood cyclothem is absent, base of Arnoldsburg is considered to lie above roof shale of Sewickley coal bed. Where base of cyclothem is drawn at this position, its average thickness is 71 ft. Under these circumstances, Sewickley sandstone, Tyler redbed, and Benwood limestone members are placed in Arnoldsburg cyclothem.

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