Assigned to Bighorn group as lower of two formations in subsurface of Williston basin. Cores studied are from wells in Roosevelt, Dawson, Wibaux and Fallon Cos, MT. Overlies Winnipeg formation; underlies Stony Mountain formation (revised) of Bighorn. Cross section of wells; fossil description and distribution. Late Ordovician (Cincinnatian) age.
Source: GNU records (USGS DDS-6; Denver GNULEX).
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