Pg. 132, Mimeo. Sheep Pen Canyon formation. Tan to buff massive and thin-bedded sandstone, 0 to 68 feet thick. Of Triassic(?) age. Unconformably underlies La Plata group and overlies Sloan Canyon formation.
[Origin of name not stated.]

Source: US geologic names lexicon (USGS Bull. 896, p. 1974).

Pg. 40-43. Sheep Pen sandstone. Buff to tan sandstone, thin-bedded to massive, unconformably underlying Exeter sandstone and conformably overlying Sloan Canyon formation. At type locality, where it caps a small mesa in E/2 NW/4 sec. 35, T. 32 N., R. 35 E., it is 68 feet thick. In places completely removed by erosion. Named from Sheep Pen Canyon, Cimarron Valley, Union County, northeastern New Mexico, which joins the Cimarron Valley about 0.5 mi northwest of type locality. Tentatively assigned to Triassic(?). Has been confused with Exeter sandstone.

Source: US geologic names lexicon (USGS Bull. 896, p. 1974).

Pg. 35 (table 2), 40-42. Sheep Pen sandstone. Uppermost formation of Dockum group. Thin-bedded light-brown sandstone. Thickness as much as 107 feet; 10 to 20 feet at most places. Overlies Sloan Canyon formation; underlies Exeter sandstone. Age is Late Triassic.
[According to GNU records (USGS DDS-6; Denver GNULEX, June 24, 1986), authors state formation is thin-bedded to massive, tan to buff sandstone, 0 to 170 feet thick in Dry Cimarron Valley.]

Source: US geologic names lexicon (USGS Bull. 1200, p. 3562-3563); GNU records (USGS DDS-6; Denver GNULEX).

Removed from Dockum Group, a name not used in the Dry Cimarron valley, Union Co, NM, because of its prior application to rocks of various lithologies and ages. Type section measured [also designated? in this report] in N1/2 SW1/4 NE1/4 sec 35, T32N, R35E, Union Co on the Sierra Grande uplift where Sheep Pen: overlies Sloan Canyon Formation of Dockum; is 16.8 m thick; has an erosional upper surface; locally disconformably underlies Entrada Sandstone; consists of sandstone that may be gray-orange, yellow-orange, red-brown, very fine, fine- or medium-grained, well rounded to subangular, poorly, moderately to well sorted, non-, slightly to moderately calcareous, silty, bioturbated, planar bedded, laminated, or ripple laminated. Cross sections; correlation chart. Is well exposed from Peacock Canyon, NM, into Cimarron Co, OK in the Palo Duro basin. Reptilian footprints, amphibian fossils, trace fossils, and bedding characteristics suggest braided stream and lacustrine environment during Sheep Pen time. Of Norian age.

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