Cutoff Formation
{{Short description|Geologic formation in Texas and New Mexico, US}}
{{Infobox rockunit
| name = Cutoff Formation
| image =
| caption =
| type = Formation
| age = {{fossilrange |Cisuralian|Guadalupian|Cisuralian to Guadalupian}}
| period = Permian
| prilithology = Shale
| otherlithology =
| namedfor = Cutoff Mountain
| namedby = King
| year_ts = 1942
| region = Texas
New Mexico
| country = United States
| coordinates = {{coord|32.002|N|104.921|W|display=inline}}
| unitof =
| subunits =
| underlies = Cherry Canyon Formation
Brushy Canyon Formation
| overlies = Bone Spring Formation
Victorio Peak Formation
| thickness = {{convert|233|ft||sp=us}}
| extent =
| area =
| map = {{Location map+ | United States#New Mexico
| relief = 1
| width = 250
| float = center
| places =
{{Location map~ | United States#New Mexico
| lat_deg = 32.002
| lon_deg = -104.921
| mark = Red pog.svg
| marksize = 12
}}
}}
| map_caption =
}}
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 {{convert|233|ft||sp=us}}{{cite journal |last1=Boyd |first1=D.W. |title=Permian sedimentary facies, central Guadalupe Mountains, New Mexico |journal=New Mexico Bureau of Geology & Mineral Resources Bulletin |date=1958 |volume=49 |pages=13-14 |url=https://geoinfo.nmt.edu/publications/monographs/bulletins/49/ |access-date=17 February 2022}} 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.{{cite encyclopedia |last1=Kues |first1=B.S. |last2=Giles |first2=K.A. |year=2004 |title=The late Paleozoic Ancestral Rocky Mountain system in New Mexico |editor1-last=Mack |editor1-first=G.H. |editor2-last=Giles |editor2-first=K.A. |encyclopedia=The geology of New Mexico. A geologic history: New Mexico Geological Society Special Volume 11 |page=124 |isbn=9781585460106}} 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.{{sfn|Kues|Giles|2004|pp=100, 122, 124]}}
The formation is interpreted as a deep basin formation deposited on a drowned shelf to basin topography. It contains numerous turbidite sequences.{{cite book |last1=Amerman |first1=Robert |last2=Nelson |first2=Eric P. |last3=Gardner |first3=Michael H. |last4=Trudgill |first4=Bruce |title=Mass-transport deposits in deepwater settings |date=2011 |publisher=Society for Sedimentary Geology |location=Tulsa, Oklahoma, U.S.A. |isbn=978-1-56576-287-9 |pages=235-267 |url=https://www.researchgate.net/profile/Robert-Amerman/publication/284003689_Submarine_mass-transport_deposits_of_the_Permian_Cutoff_Formation_west_Texas_USA_Internal_architecture_and_controls_on_overlying_sand_deposition/links/5737e31408ae9ace840bf991/Submarine-mass-transport-deposits-of-the-Permian-Cutoff-Formation-west-Texas-USA-Internal-architecture-and-controls-on-overlying-sand-deposition.pdf |access-date=18 February 2022 |chapter=Submarine mass-transport deposits of the Permian Cutoff Formation, west Texas, U.S.A.: Internal architecture and controls on overlying reservoir sand deposition}}
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.
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.{{cite journal |last1=King |first1=P.B. |title=Permian of West Texas and Southeastern New Mexico: PART 2 |journal=AAPG Bulletin |date=1942 |volume=26 |issue=4 |pages=650-763 |doi=10.1306/3D933468-16B1-11D7-8645000102C1865D}}
See also
{{Portal|Earth sciences|Texas|Paleontology}}
References
{{reflist}}
Category:Permian geology of Texas
Category:Permian formations of New Mexico
Category:Shale formations of the United States
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