The Cutoff Formation is a geologic formation in Texas and New Mexico, US. It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

dating back to the Permian period.

Description

The Cutoff Formation consists of feet of thin limestone beds interbedded with dark

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

and sandstone. It grades northwards into the San Andres Formation and is likely correlative with the upper part of the

Bone Spring Formation The Bone Spring Formation is a geologic formation found in the Delaware Basin in Texas and New Mexico. It preserves fossils dating back to the Leonardian Age of the Permian Period. Description The formation consists of dark gray deep marine lime ...

within the

Delaware Basin The Delaware Basin is a geologic depositional and structural basin in West Texas and southern New Mexico, famous for holding large oil fields and for a fossilized reef exposed at the surface. Guadalupe Mountains National Park and Carlsbad Cavern ...

. In age, the formation straddles the

Cisuralian The Cisuralian is the first Series (stratigraphy), series/Epoch (geology), epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian (geology), Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the w ...

- Guadalupian boundary. It lies atop the

Victorio Peak Victorio Peak is a high rocky outcropping in the Hembrillo Basin in southern New Mexico. This was one of Chief Victorio's hideouts, and was the site of a battle in 1880 between Victorio's Apaches and the U.S. Army Ninth Cavalry "Buffalo Soldi ...

and is overlain by the

Brushy Canyon Formation The Brushy Canyon Formation is a Permian geologic unit in Guadalupe Mountains National Park. The formation contains fan sandstones that were deposited under ancient seawater during the Middle Permian The Guadalupian is the second and middle seri ...

Cherry Canyon Formation The Cherry Canyon Formation is a geologic formation found in the Delaware Basin of southeastern New Mexico and western Texas. It contains fossils characteristic of the Guadalupian Age of the Permian Period.Kues and Giles 2004, p.100 Description ...

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

Fossils

Limestone beds of the formation contain chonetid brachiopods (''

Chonetes ''Chonetes'' is an extinct genus of brachiopods. It ranged from the Late Ordovician to the Middle Jurassic. Species The following species of ''Chonetes'' have been described: * ''C. (Paeckelmannia)'' * ''C. baragwanathi'' * ''C. billingsi' ...

'') 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 Pseudogastrioceratinae is one of two subfamilies of the Paragastrioceratidae family. They are an extinct group of ammonoid, which are shelled cephalopods related to squids, belemnites, octopuses, and cuttlefish, and more distantly to the ...

'' and ''

Perrinites Perrinitinae is one of two subfamilies of the Perrinitidae family. They are an extinct group of ammonoid, which are shelled cephalopods related to squids, belemnite Belemnitida (or the belemnite) is an extinct order of squid-like cephalopo ...

hilli'', the natiloid ''

Foordiceras Koninckioceratidae is a family of nautilid genera, typically with more or less evolute shells with depressed whorl sections, that are combined as a family within the Tainocerataceae. As perceived, the Koninckioceratidae contains 11 genera and ...

'', 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.

References

Permian geology of Texas Permian formations of New Mexico {{Permian-stub

Description

Fossils

History of investigation

See also

References