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