Cutoff Formation

Cutoff Formation
Stratigraphic range: Cisuralian to Guadalupian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Underlies	Cherry Canyon Formation Brushy Canyon Formation
Overlies	Bone Spring Formation Victorio Peak Formation
Thickness	233 feet (71 m)
Lithology
Primary	Shale
Location
Coordinates	32.002°N 104.921°W / 32.002; -104.921
Region	Texas New Mexico
Country	United States
Type section
Named for	Cutoff Mountain
Named by	King
Year defined	1942
Cutoff Formation (the United States) Show map of the United States Cutoff Formation (New Mexico) Show map of New Mexico

The Cutoff Formation is a geologic formation in Texas and New Mexico, US. It preserves fossils dating back to the Permian period.

Description

The Cutoff Formation consists of 233 feet (71 m)[1] feet of thin limestone beds interbedded with dark shale and sandstone. It grades northwards into the San Andres Formation and is likely correlative with the upper part of the Bone Spring Formation within the Delaware Basin. In age, the formation straddles the Cisuralian - Guadalupian boundary.[2] It lies atop the Victorio Peak or Bone Spring Formation and is overlain by the Brushy Canyon Formation or Cherry Canyon Formation. Both these formations fill paleocanyons cut deeply in the Cutoff Formation, in some cases cutting clear through to the underlying Bone Springs or Victorio Peak beds.[3]

The formation is interpreted as a deep basin formation deposited on a drowned shelf to basin topography. It contains numerous turbidite sequences.[4]

Fossils

Limestone beds of the formation contain chonetid brachiopods (Chonetes) and gastropods. The formation includes a few massive limestone beds that contain a diverse assemblage of fossils, including fusulinids, corals, and crinoids. Other fossils include the shark Helicoprion, the ammonoids Pseudogastrioceras and Perrinites hilli, the nautiloid Foordiceras, and the fusulinid Parafusulina.[1]

History of investigation

The unit was first designated as the Cutoff shaly member of the Bone Spring Limestone by P.B. King in 1942, for exposures on the west face of Cutoff Mountain near the New Mexico - Texas border.[5]

See also

• List of fossiliferous stratigraphic units in Texas
• Paleontology in Texas

References

1. Boyd, D.W. (1958). "Permian sedimentary facies, central Guadalupe Mountains, New Mexico". New Mexico Bureau of Geology & Mineral Resources Bulletin. 49: 13–14. Retrieved 17 February 2022.
2. Kues, B.S.; Giles, K.A. (2004). "The late Paleozoic Ancestral Rocky Mountain system in New Mexico". In Mack, G.H.; Giles, K.A. (eds.). The geology of New Mexico. A geologic history: New Mexico Geological Society Special Volume 11. p. 124. ISBN 9781585460106.
3. Kues & Giles 2004, pp. 100, 122, 124].
4. Amerman, Robert; Nelson, Eric P.; Gardner, Michael H.; Trudgill, Bruce (2011). "Submarine mass-transport deposits of the Permian Cutoff Formation, west Texas, U.S.A.: Internal architecture and controls on overlying reservoir sand deposition". Mass-transport deposits in deepwater settings (PDF). Tulsa, Oklahoma, U.S.A.: Society for Sedimentary Geology. pp. 235–267. ISBN 978-1-56576-287-9. Retrieved 18 February 2022.
5. King, P.B. (1942). "Permian of West Texas and Southeastern New Mexico: PART 2". AAPG Bulletin. 26 (4): 650–763. doi:10.1306/3D933468-16B1-11D7-8645000102C1865D.