Wikipedia

San Jose Formation

For other uses, see San José Formation.

The San Jose Formation is an Early Eocene (Wasatchian in the NALMA classification) geologic formation in the San Juan Basin of New Mexico and Colorado.[1]

San Jose Formation
Stratigraphic range: Wasatchian
~55.8–50 Ma
San Jose Formation capping Mesa de Cuba, northern New Mexico
TypeFormation
Sub-unitsCuba Mesa, Ditch Canyon, Llaves, Regina & Tapicitos Members
OverliesNacimiento Formation
Thickness430 m (1,410 ft)
Lithology
PrimarySandstone
OtherShale
Location
Coordinates36°17′N 107°04′W / 36.29°N 107.06°W / 36.29; -107.06
Approximate paleocoordinates41°12′N 91°42′W / 41.2°N 91.7°W / 41.2; -91.7
RegionNew Mexico
Country United States
ExtentSan Juan Basin
Type section
Named forSan Jose Valley (36°10′48″N 106°55′37″W / 36.180°N 106.927°W / 36.180; -106.927)
Named byG.G. Simpson
Year defined1948
San Jose Formation is located in the United States
San Jose Formation
San Jose Formation (the United States)
San Jose Formation is located in New Mexico
San Jose Formation
San Jose Formation (New Mexico)

Description

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Road cut in the San Jose Formation, near Cuba, New Mexico

The San Jose Formation is mostly sandstone but with some mudstone beds.[2][3] The formation was deposited by high-energy streams on a muddy floodplain that was the last preserved sedimentation episode in the San Juan Basin. Stream direction was from the northwest, north, and east towards the south.[4]

The basal Cuba Mesa Member is found throughout the depositional basin and is a coarse-grained sheet sandstone. The Regina Member is floodplain mudstone and disconnected sheet sandstone that intertongues with the sandstone-dominated Ditch Canyon Member in the northwestern part of the basin and the Llaves Member on the east side of the basin. The uppermost member is the siltstone-dominated Tapicitos Member. The Cuba Mesa Member was deposited during subsidence in the basin center, while the later members were deposited during episodes of monoclinal folding along the Nacimiento Fault on the west escarpment of the Nacimiento Mountains.[4]

Paleontology

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The mudstone beds of the San Jose Formation are locally rich in fossils.[2] These include the Almagre and Largo faunas of the early Eocene.[5]

Fossil content

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Among others, the following fossils have been reported from the formation:[1]

Mammals

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Primates
Artiodactyls
Carnivora
Cimolesta
Ferae
Glires
Hyaenodonta
Insectivora
Pantodonta
Perissodactyla
Placentalia
Taeniodonta
Theriiformes

Reptiles

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Snakes
Turtles
Lizards

History of investigation

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In late 1874, Edward Drinker Cope was a member of the Wheeler Survey but ignored orders from Wheeler to proceed north from the Chama River to Colorado. Instead, he headed south to explore the area north of the San Pedro Mountains, where fossils had been reported. He found early Eocene fossils in the badlands north of Regina, New Mexico and spent about seven weeks collecting fishes, reptiles, and what was then the oldest known mammal fossils in North America. He also collected the fossil of a giant flightless bird. Cope later wrote his father that this was "the most important find in geology I have ever made".[25][26]

In 1948, G.G. Simpson visited the same area and assigned the fossil beds to the San Jose Formation.[2] In 1967, the formation was divided (in ascending order) into the Cuba Mesa Member, Regina Member, Llaves Member, and Tapicitos Member.[5]

See also

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References

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  1. ^ a b San Jose Formation at Fossilworks.org
  2. ^ a b c Simpson 1948a.
  3. ^ Simpson 1948b.
  4. ^ a b Smith 1992.
  5. ^ a b Baltz 1967.
  6. ^ Gingerich & Simons 1977.
  7. ^ a b c d e f g Lucas, Schoch & Manning 1981.
  8. ^ a b c d e f g h i j k Alroy 2002.
  9. ^ a b Beard 1987.
  10. ^ a b Krishtalka & Stucky 1986.
  11. ^ Denison 1938.
  12. ^ Korth 1984.
  13. ^ Flanagan 1986.
  14. ^ Bown & Schankler 1982.
  15. ^ a b Froehlich 2002.
  16. ^ a b c Redline 1997.
  17. ^ a b Simpson 1951.
  18. ^ Williamson & Lucas 1992.
  19. ^ Schoch 1986.
  20. ^ a b c d e f g Sullivan & Lucas 1988.
  21. ^ a b c d e f Lichtig & Lucas 2015.
  22. ^ Hay 1904.
  23. ^ Cope 1875.
  24. ^ a b Lichtig, Hutchison & Lucas 2018.
  25. ^ Osborn 1978.
  26. ^ Kues, Lewis & Lueth 2014.

Bibliography

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