The formation is divided into the Macho Member, which is a massive ledge-forming limestone breccia (thickness 30 feet (9.1 m));[1][4] the Turquillo Member, a thick-bedded mudstone;[3] the Manuelitas Member, which is a light to medium gray calcarenite, limestone-pebble conglomerate, and finely crystallized locally cherty limestone (thickness 39 feet (12 m)); and the Cowles Member, which is a light yellow gray to olive yellow cross-bedded silty calcarenite (thickness 50 feet (15 m).[1][4]
Fossils
The Manuelitas Member contains fossils of the foraminiferanEndothyra sp. of Meramecian (Visean) age. [2] The Macho, Turquillo, and Manuelitas Members contain microfossils characteristic of the Meramecian while the Cowles Member contains microfossils characteristic of the Chesterian (late Visean and Serpukhovian).[3]
History of investigation
The formation was first defined by Baltz and Read in 1960.[1] Armstrong and Mamet included it as the upper formation of their Arroyo Penasco Group in 1974 and added the Turquillo Member.[3]
^ abcdefBaltz, Elmer H.; Read, Charles B. (1960). "Rocks of Mississippian and Probable Devonian Age in Sangre de Cristo Mountains, New Mexico". AAPG Bulletin. 44. doi:10.1306/0BDA623C-16BD-11D7-8645000102C1865D.
^ abSutherland, P.K. (1963). "Paleozoic rocks"(PDF). In Miller, J.P.; Montgomery, Arthur; Sutherland, P.K. (eds.). Geology of part of the southern Sangre de Cristo Mountains, New Mexico: New Mexico Bureau of Mines and Mineral Resources Memoir 11. pp. 22–44. Retrieved 29 July 2020.