Named as the basal member of the Frontier formation and as one of ten named members in the Frontier at Coalville, Summit Co, UT on the Uinta uplift. Name "Longwall" derived from its outcrop form as a conspicuous white wall. The sandstone supports a prominent escarpment north of the apex of the Coalville anticline. No type locality designated. Is a regressive marine gray to white sandstone representing the first complete transgression into the area after Aspen time. Is 70 ft thick in its western area [location not specified] and 100 ft thick in its eastern area [area not stated]. Correlates with upper part of the Aspen shale of the Cumberland Gap, Lincoln Co, WY in the Greater Green River basin. Location of nomenclature change not stated. Overlies Aspen? shale. Underlies Spring Canyon member (new) of Frontier. Cross sections. Correlation chart. Of late Albian, Early Cretaceous age.

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