Named as a member of Pleistocene Osprey Formation for exposures on east side of the Narrows of the Yellowstone River Canyon directly across from Caleite Springs and 5,800 ft north 30 degrees west of mouth of Tower Creek (its type section), Yellowstone National Park, Yellowstone province, WY. Rests on Eocene volcanic breccias and is overlain by Pinedale Till at type. Consists of cobble-size rocks of Eocene volcanics (65 percent), quartz-bearing rhyolite (5-15 percent), upper Cenozoic basalt (5-25 percent), quartzite and Precambrian crystallines (5-15 percent). A 5 ft thick ash bed is 60 ft above base of Osprey Formation at type of Tower Creek Member. Is restricted to the gravel part of Osprey. Is interbedded with black, very fine grained, dense, columnar-jointed basalt flows. Age assigned to the Pleistocene; determined by position above Yellowstone Tuff or Eocene volcanics, and below glacial deposits.

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

Inclusion of Tower Creek Gravel Member is Osprey considered erroneous. Sediments and basalts of The Narrows excluded from Osprey, whose name is changed from Osprey Formation to Osprey Basalt.

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