The Lower Permian Abo Formation in the northern Sacramento Mountains, southern New Mexico
— Spencer G. Lucas, Karl Krainer, Sebastian Voigt, David S. Berman, and Amy Henrici

We describe the lithostratigraphy, sedimentary petrography and vertebrate paleontology of the thickest known (~ 400 m thick) section of the Lower Permian Abo Formation, which is in the northern Sacramento Mountains of Otero County, New Mexico. This Abo section differs from other sections of the formation in its great thickness, lack of a clear subdivision into lower, mudstone-dominated and upper sandstone-dominated intervals (instead, it is a section of interbedded mudstone and sandstone/conglomerate without obvious subdivisions), and the presence of numerous beds of extrabasinal conglomerate, especially beds of basement-cobble conglomerate in the lower part. This lithologically distinct Abo lithosome is recognized by us as a new member of the Abo Formation, the Coyote Hills Member. The Coyote Hills Member is dominantly mudstone and siltstone representing floodplain deposits with intercalated conglomerate-sandstone sheets of a low sinuosity river system and thinner debris-flow conglomerates, small, thin channel-fill sandstones, and thin tabular sheetflood and splay sandstones. These strata were deposited in a more proximal facies compared to the Abo Formation in central and southern New Mexico, with higher amounts of basement-derived conglomerate and coarse-grained sandstone. Sediments were derived from a local source area in the Pedernal uplift composed mainly of granitic and granophyric rocks and deposited on an extensive alluvial plain that extended southward and southwestward toward the Hueco seaway. Fossils from the Coyote Hills Member are a few trace fossils and bones of fish, amphibians and pelycosaurs that are an assemblage of Coyotean (late Virgilian-late Wolfcampian) age. Regional correlation of the Abo Formation in the Sacramento Mountains suggests it is of middle-late Wolfcampian (and possibly early Leonardian) age.