New Mexico Geology

The boundary between Middle and Upper Pennsylvanian strata in central New Mexico is generally considered to coincide with the contact between the Gray Mesa and the overlying Atrasado formations. This perception was advanced in the Manzano Mountains by D.A. Myers, who reported the early Missourian fusulinid Eowaeringella near the top of the Gray Mesa Formation from a single locality in Gotera Canyon at the northern end of the range. The Gotera Canyon locality was re-examined and the Eowaeringella horizon recovered, together with additional strata 20 to 25 meters higher in the section that contain early forms of Triticites, including T. cf. pygmaeus, T. wellsi, and T. cf. planus. Thus, at Gotera Canyon, the Eowaeringella Zone is present 50 meters above the top of the Gray Mesa Formation, near the base of the Tinajas Member of the Atrasado Formation. The overlying Triticites-bearing strata appear to be common in the lower part of the Tinajas Member, from as far south as the Gotera Canyon locality northward to the Sandia Mountains.