The Triassic System in the Dry Cimarron Valley, New Mexico
Spencer G. Lucas, A. P. Hunt, and Steven N. Hayden
Triassic continental sediments exposed in the Dry Cimarron Valley pertain to the Baldy Hill (oldest), Travesser, Sloan Canyon and Sheep Pen formations. The Baldy Hill Formation is at least (its base is nowhere exposed) 37 m of yellowish orange and reddish brown, bioturbated, quartzose sandstone and siltstone capped by as much as 3 m of lithic- and limestone-cobble conglomerate here named the Cobert Canyon Sandstone Bed. The Baldy Hill Formation crops out both in New Mexico and Oklahoma (sec. 18, T5N, R6E) where the Cobert Canyon Sandstone Bed contains fossils of metoposaurid labyrinthodonts and phytosaurs indicative of a Late Triassic age. The Baldy Hill-Travesser contact is a disconformity, not the angular unconformity previously reported. The Travesser Formation is as much as 168 m of reddish brown, laminar and ripple-laminar, quartzose sandstone, siltstone and minor lithic conglomerate. The uppermost Travesser (not the Sloan Canyon as reported previously) produced the phytosaur skull Stovall and Savage (1939) described and contains other Late Triassic vertebrates and unionids. A marked color change to the yellowish green and greenish gray siltstone, sandstone and limestone of the Sloan Canyon Formation (as much as 41 m) marks the Travesser-Sloan Canyon contact. Abundant microvertebrates and reptilian footprints in the Sloan Canyon are of Late Triassic age. The Sloan Canyon-Sheep Pen contact is gradational, and the latter is as much as 33 m of yellowish orange, laminar, quartzose sandstone with a Scoyenia-facies ichnofauna. An angular unconformity separates the Triassic strata in the Dry Cimarron Valley from the overlying Middle Jurassic Entrada Sandstone. The Triassic strata in the Dry Cimarron are dominantly of lacustrine origin. They are of Late Triassic age, and probably transgress the Camian-Norian boundary. Lithologic dissimilarity of the Dry Cimarron Triassic and the Triassic strata to the south in the Tucumcari and Palo Duro basins suggests Late Triassic deposition in a separate Dry Cimarron basin northeast of the Sierra Grande uplift and north of the Bravo dome.
- Lucas, Spencer G.; Hunt, A. P.; Hayden, Steven N., 1987, The Triassic System in the Dry Cimarron Valley, New Mexico, in: Northeastern New Mexico, Lucas, S. G.; Hunt, A. P., New Mexico Geological Society, Guidebook, 38th Field Conference, pp. 97-117.