Named for the town of Picabo about 15 mi southwest of the Fish Creek Reservoir, Blaine Co, ID in the Snake River basin. Type section measured in NE1/4 sec 10, T1N, R22E where Picabo overlies Jefferson Formation and underlies Copper Basin Formation. Lower contact is covered; upper contact is a thrust fault. Is 189+ ft thick at type where it consists of: 1) lower gray, fine-grained, laminated, quartzitic sandstone interbedded with laminated sandy gray dolomite; 2) middle interbedded dolomite conglomerate and dolomitic sandstone; and 3) upper gray to red, very fine to fine-grained, thin-bedded, calcareous sandstone. The conglomerate is gray to yellow brown, of well-rounded to tabular pebbles with diameters as large as 5 in, derived from underlying Jefferson or from Carey Dolomite (new). Is nonfossiliferous. Presumed to be very late Devonian because of stratigraphic position. Geologic map, columnar section. Is a shelf-facies rock.

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

Extended into the structural Dry Canyon window in northeastern part of Hailey 1 X 2 deg quad, Custer Co, ID, Idaho Mountains province. Overlies Jefferson Formation; upper contact is a fault [shown on geologic map (fig. 2) to be in contact with Mississippian Copper Basin Formation]. Devonian age.

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