Named as the basal member of the San Jose Formation for exposures on upper slopes and top of Mesa de Cuba west of Rio Puerco, T21N, Rs 1 and 2W, Sandoval Co, NM in San Juan basin. Type section measured along State Hwy 44 northwest of Cuba in NE1/4 NW1/4 sec 20 across secs 17, 8, 7, and 6, T21N, R1W, and secs 1 and 2, T21N, R2W. Is 699 ft thick at type where it overlies Nacimiento Formation, and intertongues with and underlies Regina Member (new) of San Jose. Present throughout report area. Is 200-250 ft thick in subsurface. Consists of buff and yellow, rusty-weathering, tangentially cross bedded, arkosic, coarse-grained, conglomeratic sandstone. The sand is mainly quartz, but feldspar and chert common. Most pebbles are gray quartzite or chert, though granite, pink quartzite and pink, red, buff and gray chert, and a few of volcanic rocks. The sand grains are angular to subangular. The pebbles are rounded. Lower part contains several thin lenses of gray and purplish-gray sandy shale. The base of the lower sandstone is a channeled erosion surface. Northeast of type two sandstone tongues of Cuba Mesa merge with Regina. Is overlain by Llaves Member at east side Yeguas Mesas north of Canoncito de las Yeguas. Is of early Eocene age. Geologic map. Correlation chart. Cross sections. Measured sections.

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