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Mesaverde Group

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Mesaverde Group
Stratigraphic range: Late Cretaceous
Mesaverde Group beds in the Book Cliffs near Helper, Utah.
TypeGroup
Sub-unitsSee text
UnderliesLewis Shale, Meeteetse Formation, Datil Group (regionally)
OverliesCody Shale, Mancos Shale
Thickness200–400 metres (660–1,310 ft)
Lithology
Primarysandstone and shale
Othercoal
Location
Coordinates37°18′58″N 108°25′08″W / 37.316°N 108.419°W / 37.316; -108.419
ExtentNew Mexico, Utah, Wyoming
Type section
Named forMesa Verde, Colorado
Named byW.H.Holmes (1877)
Mesaverde Group is located in the United States
Mesaverde Group
Mesaverde Group (the United States)
Mesaverde Group is located in Colorado
Mesaverde Group
Mesaverde Group (Colorado)


History edit

The Mesaverde Formation was first described by W.H.Holmes in 1877 during the Hayden Survey. Holmes described the formation in the northern San Juan Basin as consisting of three units, which were a "Lower Escarpment" consisting of 40 m of ledge- and cliff-forming massive sandstone; a "Middle Coal Group" consisting of up to 300 m of thick slope-forming sandstone, shale, marl, and lignite; and an "Upper Escarpment" consisting of 60 m of ledge- and cliff-forming sandstone.[1] A.J. Collier redesignated these units in 1919 as the Point Lookout Sandstone, the Menefee Formation, and the Cliff House Sandstone, and raised the Mesaverde Formation to group rank.[2]

The group was later traced to the greater Green River Basin,[3] the Uintah and Piceance Basins,[4] the Bighorn Basin,[5] the Front Range,[6] the Zuni Basin,[7] the Wasatch Plateau,[8] Wind River Basin,[9] Washakie Basin,[10] and the Powder River Basin.[11] It is spectacularly exposed along the Book Cliffs of eastern Utah and western Colorado.[12] With the recognition of the vast extent of the group, the group has been divided into formations by region, with the original Point Lookout Sandstone, Menefee Formation, and Cliff House Sandstone being restricted largely to the San Juan Basin and the Madrid, New Mexico area.

Geology edit

 
Stratigraphic column showing the relationship of the Mesaverde Group

The Mesaverde Group is a Late Cretaceous stratigraphic group found in areas of Colorado, New Mexico, Utah, and Wyoming, in the Western United States. The group is a single regression-transgression sequence in its type location in the San Juan Basin, dividing the older marine Mancos Shale and younger Lewis Shale deposited in the Western Interior Seaway. The Point Lookout Sandstone represents the regression, the Menefee Formation the subsequent fluvial delta deposits, and the Cliff House Sandstone the return of the sea. In other locations, such as along the Book Cliffs, the picture is more complicated, with multiple regression-transgression sequences from tectonic activity along the Sevier mountain front.[13] In the Cody area, the group is a simple regression sequence and remains at formation rank. Here the group is described as interbedded light gray sandstone and gray shale in the upper part; massive, light-buff, ledge-forming sandstone containing thin lenticular coal beds in the lower part.[14]

Formations edit

 
Mesaverde Gas Fields within the Uinta Basin and Piceance Basin

Fossils edit

Dinosaur remains are among the fossils that have been recovered from the group, although none have yet been referred to a specific genus.[20] Deinosuchus has also been reported from Mesaverde outcrops in Wyoming.[21] In 2023, baenid turtle fossils tentatively assignable to Neurankylus sp. from the Mesaverde Formation were described.[22]

See also edit

Footnotes edit

  1. ^ Holmes 1877.
  2. ^ a b Collier 1919.
  3. ^ Fenneman & Gale 1906.
  4. ^ Lee 1909.
  5. ^ Lupton 1916.
  6. ^ Ball 1924.
  7. ^ Sears 1925.
  8. ^ Spieker & Reeside 1925.
  9. ^ Barwin 1959.
  10. ^ Hale 1961.
  11. ^ a b Fox 1993.
  12. ^ Fillmore 2011, p. 224.
  13. ^ Fillmore 2011, pp. 240 et seq..
  14. ^ Pierce 1997.
  15. ^ a b Johnson 1989.
  16. ^ Molenaar 1983.
  17. ^ Nummedal & Molenaar 1995.
  18. ^ Fouch et al. 1992.
  19. ^ Roehler 1987.
  20. ^ Weishampel, Dodson & Osmólska 2004, pp. 517–607, "Dinosaur distribution".
  21. ^ Wahl & Hogbin 2003.
  22. ^ Jarne, Philippe; Lozano del Campo, Ana; Lamy, Thomas; Chapuis, Elodie; Dubart, Maxime; Segard, Adeline; Canard, Elsa; Pointier, Jean-Pierre; David, Patrice (2021-11-25). "Connectivity and selfing drives population genetic structure in a patchy landscape: a comparative approach of four co-occurring freshwater snail species". Peer Community Journal. 1. doi:10.24072/pcjournal.29. hdl:20.500.12210/58455. ISSN 2804-3871. S2CID 244705430.

References edit

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