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The Cutoff Formation is a
geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...
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 Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...
.


Description

The Cutoff Formation consists of feet of thin limestone beds interbedded with dark shale and sandstone. It grades northwards into the San Andres Formation and is likely
correlative In grammar, a correlative is a word that is paired with another word with which it functions to perform a single function but from which it is separated in the sentence. In English, examples of correlative pairs are ''both–and, either–or, nei ...
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 Cave ...
. In age, the formation straddles the
Cisuralian The Cisuralian is the first series/epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the western slopes of the Ural Mountains in Russia and Kazakhstan and ...
- Guadalupian boundary. It lies atop the Victorio Peak or
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 ...
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 ...
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. The formation is interpreted as a deep basin formation deposited on a drowned shelf to basin topography. It contains numerous
turbidite A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing Turbidites were ...
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 Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...
, and
crinoids Crinoids are marine animals that make up the Class (biology), class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or coma ...
. Other fossils include the shark ''
Helicoprion ''Helicoprion'' is an extinct genus of shark-like eugeneodont fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls", which in life were embedded in the lower jaw. As with most extin ...
'', the
ammonoids Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish ...
'' Pseudogastrioceras'' and '' Perrinites hilli'', the natiloid '' 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.


See also

*
List of fossiliferous stratigraphic units in Texas This article contains a list of fossil-bearing stratigraphic units in the state of Texas, U.S. Sites See also * Paleontology in Texas References * * {{DEFAULTSORT:Fossiliferous stratigraphic units in Texas Fossil Texas Te ...
*
Paleontology in Texas Paleontology in Texas refers to paleontological research occurring within or conducted by people from the U.S. state of Texas. Author Marian Murray has remarked that "Texas is as big for fossils as it is for everything else." Some of the most imp ...


References

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