Named after Ledge Creek, tributary of Sadlerochit River, as middle member (of 3) of Ivishak Formation. Type section designated as section exposed along small eastern tributary of Marsh Creek on north side of Sadlerochit Mountains, 69 deg 41'N, 144 deg 50'30"W, northeastern AK. Best developed along north side of Brooks Range in Sadlerochit and Shublik Mountains. Is main producing unit in subsurface at Prudhoe Bay. Is primarily clean, massive, medium light gray to dark reddish brown quartz arenite. Cross-bedding, ripple marks, ball-and-pillow structures, and flute casts are common features. Is 189 ft thick at type. Conformably overlies Kavik Member; conformably underlies Fire Creek Siltstone Member (both new and of Ivishak Formation). Age is Early Triassic based on ammonites of Romunderi Zone (Smithian) age and age of underlying Kavik Member.

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

In subsurface Prudhoe Bay area "Ledge Sandstone Member of Ivishak Formation" of Detterman and others (1975) is called "Ivishak Sandstone" of Sadlerochit Group. Overlies "Kavik Shale" of Sadlerochit Group. Underlies thin, phosphatic, radioactive conglomerate which is overlain by mudstones of Shublik Formation. Ivishak Sandstone is tentatively assigned to Late Permian and Early Triassic age based on palynological data.

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