The Seven Rivers 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 exp ...

in southeastern

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

and west

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

. 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 ...

dating back to the late

Guadalupian The Guadalupian is the second and middle Series (stratigraphy), series/Epoch (geology), epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico an ...

Epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

of the

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

Description

The formation consists of of

anhydrite Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...

, with interbeds of

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

, dolomite,

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

, and

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

. It rests on the Queen Formation and is overlain by the Yates Formation. The Seven Rivers Formation is part of the Artesia Group, which is interpreted as a sequence of shelf rocks of the Capitan reef.

History of investigation

The unit was first named as the Seven Rivers Member of the (now abandoned) Chupadera Formation by Oscar Edward Meinzer and coinvestigators in 1927. In 1937, W.B. Lang assigned the Seven Rivers Member to the (now abandoned) Chalk Bluff Formation and removed its upper beds to the Three Twins Member. The unit was promoted to formation rank and assigned to the Whitehorse Group by Ronald K. DeFord and E. Russel Lloyd in 1940.

Norman D. Newell Norman Dennis Newell (January 27, 1909 – April 18, 2005) was a professor of geology at Columbia University, and chairman and curator of invertebrate paleontology at the American Museum of Natural History in New York City. Early life and educati ...

and coinvestigators assigned the formation to the (now abandoned) Carlsbad Group in 1953, and it was assigned to the Artesia Group by D.B. Tait and coinvestigators in 1962. File:7 Rivers Fm.jpg, Shales and gypsum of the Seven Rivers Formation, Bottomless Lakes State Park, New Mexico File:7 Rivers Gypsum.jpg, Weathered face of gypsum in the Seven Rivers Formation, Bottomless Lakes State Park, NM. Note the dark, irregular reprecipitated gypsum

Footnotes

References

* * * * * * * {{cite journal , last1=Tait , first1=D.B. , last2=Motts , first2=W.S. , last3=Spitler , first3=M.E. , year=1962 , title=Artesia Group of New Mexico and West Texas , journal=American Association of Petroleum Geologists Bulletin , volume=46 , number=4 , pages=504–517 , doi=10.1306/BC74383B-16BE-11D7-8645000102C1865D Permian formations of New Mexico Shale formations of the United States Siltstone formations of the United States Dolomite formations of the United States Sandstone formations of the United States

Description

History of investigation

See also

Footnotes

References