Named as a tongue in the lower part of the Green River Formation for exposures (type section) in east wall of canyon of Middle Fork across border between NE1/4 sec 19 and SE1/4 sec 18, T10S, R8E, Utah Co, UT on the Wasatch uplift. Extent of tongue beyond report area not discussed. Consists of tan-brown paper shale of fluviatile origin, some beds of which may be ostracodal, petroliferous, kerogenaceous. Some beds have concretions. Shale is interbedded with grayish- or greenish-brown, thin-bedded marlstone, and tan to buff and light-brown, thin-bedded to massive, ostracodal, petroliferous limestone. Contains several coquina beds of gastropod and pelecypod fragments up to 4 ft thick. Type section measured. Is 280 ft thick at type. Thins eastward. Is 250 ft thick east of town of Colton. Ostracod species identified. Unit beneath Middle Fork not discussed; lower contact not described. Overlain by fluviatile beds of Tabbyune Creek Tongue of Colton. Stratigraphic charts. Eocene age.

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