The Mojado Formation is a geologic formation in southwestern New Mexico. It preserves fossils dating back to the early Cretaceous period.

Description

The formation consists mostly of sandstone and shale, with some limestone, and siltstone. It rests conformably on the U-Bar Formation and is unconformably overlain by the Cowboy Spring Formation.The total thickness is 5,150–7,800 feet (1,570–2,380 m).

Lucas and his coinvestigators assigned the formation to the Bisbee Group and divided it into the Fryingpan Spring, Sarten, Beartooth, and Rattlesnake Ridge members.

The Fryingpan Spring Member is interpreted as continental deltaic sedimentation. The Sarten Member is fluvial while the Rattlesnake Ridge Member represents a return to shallow marine conditions.

Fossils

The formation contains fossil mollusks such as gastropods, ammonites, and pelecypod, foraminifera, and scaphopods. These date the formation to the late Albian.

History of investigation

The formation name was first used by Zeller in 1962, but he did not formally name the formation until 1965. In 1998, Lucas and coinvestigators assigned the formation to the Bisbee Group and divided it into the Fryingpan Spring, Sarten, Beartooth, and Rattlesnake Ridge members. However, Lawton abandoned the Beartooth Member in 2004.

See also

Footnotes

  • Hayes, P.T. (1970). . U.S. Geological Survey Professional Paper. 658-B: B1–B42. doi:.
  • Lawton, Timothy F. (2004). "Upper Jurassic and lower Cretaceous strata of southwestern New Mexico and northern Chihuahua, Mexico". In Mack, G.H.; Giles, K.A. (eds.). The geology of New Mexico. A geologic history: New Mexico Geological Society Special Volume 11. pp. 153–168. ISBN 9781585460106.
  • Lucas, Spencer G.; Estep, John W. (1998). . New Mexico Museum of Natural History and Science Bulletin. 14.
  • Zeller, R.A. Jr. (1962). . New Mexico Bureau of Mines and Mineral Resources Geologic Map. 17.
  • Zeller, R.A. Jr. (1965). . New Mexico Bureau of Mines and Mineral Resources Memoir. 16.
  • Zeller, R.A. Jr.; Alper, A.M. (1965). (PDF). New Mexico Bureau of Mines and Mineral Resources Bulletin. 84.