Named as one of three tongues of Dakota Sandstone for exposures on east side of Cubero Mountain about 8 mi west of Laguna, Valencia Co, NM in San Juan basin. Type section measured at NE1/4 SE1/4 sec 20 and SW1/4 NW1/4 sec 21, T10N, R5W, Laguna quad. Is mostly composed of very fine to fine-grained, silty and, in part carbonaceous, sandstone. Is 50 ft thick at type. Merges with main body of Dakota a few mi west of Grants, Valencia Co. Not recognized at Narrows, Valencia Co or at Alamo Day School, Socorro Co. Overlies Oak Canyon Member of Dakota and underlies Clay Mesa Shale Tongue of Mancos Shale at type. Has a limited fauna. Is of marine origin. Cretaceous age. Correlation chart. Measured sections; cross sections.

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

Is member of the Dakota Sandstone in the San Juan basin in west-central NM. Overlies Oak Canyon Member of Dakota Sandstone. Underlies lower part of Mancos Shale in Acoma Pueblo area; underlies Clay Mesa Tongue of Mancos in Laguna to San Ysidro area. Molluscan fossils are abundant in lower part of Cubero in the Acoma Pueblo-Seboyeta area; 18 bivalve species, 1 gastropod species, and 2 ammonite species are known from the area. Fauna of this member places it in the ammonite zone of CONLINOCERAS TARRANTENSE, of early middle Cenomanian age (Late Cretaceous). Figure 2 is stratigraphic nomenclature and correlation chart of middle Cenomanian to lower Coniacian rocks in west-central NM, spanning 20 ammonite zones.

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