Pg. 137, pl. XXI. Bird Creek limestone. Lowest limestone exposed over any considerable part of area (T. 24, 25, and 26 N., R. 6 and 7 E.; T. 25 and 26 N., R. 5 E., T. 26 N., R. 4 E.). Is a dense, fine-grained noncrystalline rock 4+/- feet thick. On fresh surface is commonly lead-gray to black and weathers to a dirty buff or yellow. When struck with hammer it breaks along bedding planes with comparatively smooth surfaces. Few fossils. Is hard and fairly resistant to erosion but does not produce a marked topographic effect. Is older than Stonebreaker limestone. Named by K.C. Heald (report in preparation [=Chapter Q, USGS Bull. 686, p. 214, 216]) from exposures in T. 27 N., R. 8 E. Age is Pennsylvanian.

Source: US geologic names lexicon (USGS Bull. 896, p. 191).

Pg. 214, 216. Bird Creek limestone. In most places where seen there is but a single bed, 2+/- feet thick, but at a few localities there are two beds separated by 6+/- feet of shale. The rock is hard and very brittle. Both weathered and fresh surfaces are dark bluish gray, so dark that many samples might be called black. Is characterized by a distinct brachiopod fauna (ENTELETES HEMIPLICATA). Lies 50+/- feet below CRYPTOZOON-bearing limestone, about 70 feet above Turkey Run limestone, and a little more than 100 feet above "red lime" at top of Pawhuska limestone. Age is Pennsylvanian. Report includes cross section.
Named from exposures on valley sides of Bird Creek and tributaries, in T. 27 N., R. 8 E., Osage Co., OK. A "good exposure" on slope in northwest corner of sec. 28, T. 27 N., R. 8 E., Osage Co., OK.

Source: US geologic names lexicon (USGS Bull. 896, p. 191); supplemental information from GNU records (USGS DDS-6; Denver GNULEX).