Pg. 61-62, pls. 1, 3. Officer Member, middle member (of 3) of Trowbridge Formation. About half black and green mudstone similar to that in underlying Rosebud Member (new). Other half made up of resistant volcaniclastic strata. The two rock types occur in alternating sequences, each 25 to 100 feet thick, that give rise to a ridge and swale topography. Within mapped area, the basal resistant sequence is a ledge-forming felsite tuff unit, informally named Buck Creek felsite tuff (Dickinson, 1962), that maintains thickness of 60 to 75 feet throughout area east of Sheep Creek, but thins rapidly to feather edge in west. Thickness 100 to 500 feet. Underlies Magill Member (new). Age is Late Jurassic (Callovian).
Type locality: Cottonwood Draw (a tributary to Rosebud Creek), in NW/4 sec. 22, T. 17 S., R. 28 E., Suplee-Izee area, Grant Co., OR. Named from Officer Creek.

Source: US geologic names lexicon (USGS Bull. 1350, p. 538); supplemental information from GNU records (USGS DDS-6; Menlo GNULEX).