Name applied to the basal shale of the Marcella Formation (new). Consists of dull black, carbonaceous, siliceous shale. Blocky or platy weathering. Weathered slopes are gray to brown color. A few thin limestone beds in upper few ft. Ranges from 0 to 60 ft thick; averages 20 ft thick; is 59 ft thick at type measured section of Marcella along intermittent tributary of Wallace Creek in NW1/4 sec 12, T13N, R9W near Marcella, Stone Co, AR in the Arkoma basin. No type locality designated. Nomenclature chart. Cross section. Overlies Pitkin Limestone. Underlies unnamed predominantly limestone part of Marcella. Isopach and lithofacies map of Marcella. Beds assigned to Wallace Creek in this report were formerly considered to be part of Pitkin Limestone. Of Late Mississippian, Chester age.

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