Dakota Formation

Dakota Formation / Group
Stratigraphic range:
Cenomanian,
around 100–95 Ma
↓
Road cut into the lower Dakota Group at crest of Dinosaur Ridge, near Golden, Colorado
TypeGeological formation or group
Sub-unitsType Location: Formation (Nebraska/Iowa):[1]

Woodbury
Nishnabotna

Formation (Kansas):
D/Johnson Clay Member
J/Terra Cotta Clay Member

Formation (San Juan Basin, etc.):[2]
Twowells Tongue
Paguate Tongue
Cubero Tongue

Formation (sw Utah):
(undivided conglomerate)

Group (Dinosaur Ridge):
South Platte Formation
Lytle Formation

Group (Denver Basin):
Muddy Formation
Skull Creek Shale
Plainview Sandstone
Lytle Formation

Group (Williston Basin):[3]
Mowry Shale
Newcastle Formation
Skull Creek Shale
Inyan Kara

Group (Colorado Plateau):[4]
Naturita Formation
Cedar Mountain Formation

Group (Dry Cimarron):[4]
Romeroville Sandstone
Pajarito Formation
Mesa Rica Sandstone
UnderliesGraneros Shale (sometimes included in the Colorado Group of the Great Plains or the Mancos Shale of the Southwest)
OverliesPrecambrian (Sioux Quartzite), Permian, Early Cretaceous (Lytle), and Jurassic (Morrison Formation)
Lithology
Primaryvarying proportions of terrestrial sandstone, mudstone, and clay, with beds of shallow marine mud [5]
Othermarine shale, lignite, coal
Location
Coordinates42°18′25″N 96°27′14″W / 42.307°N 96.454°W / 42.307; -96.454
Approximate paleocoordinates38°54′N 66°24′W / 38.9°N 66.4°W / 38.9; -66.4
RegionGreat Plains, Rocky Mountains, Colorado Plateau, Rio Grande rift valley
Country United States
 Canada
Type section
Named forDakota City, Nebraska
Named byMeek and Hayden
Year defined1862[6]
Dakota Formation is located in the United States
Dakota Formation
Dakota Formation (the United States)
Dakota Formation is located in Nebraska
Dakota Formation
Dakota Formation (Nebraska)

The Dakota is a sedimentary geologic unit name of formation and group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and shales deposited in the Mid-Cretaceous opening of the Western Interior Seaway.[7] The usage of the name Dakota for this particular Albian-Cenomanian strata is exceptionally widespread; from British Columbia and Alberta to Montana and Wisconsin to Colorado and Kansas to Utah and Arizona. It is famous for producing massive colorful rock formations in the Rocky Mountains and the Great Plains of the United States, and for preserving both dinosaur footprints and early deciduous tree leaves.

Owing to extensive weathering of older rocks during the Jurassic and Triassic, the Dakota strata lie unconformably atop many different formations ranging in age from Precambrian to Early Cretaceous. With a few local exceptions, it is the oldest Cretaceous unit exposed in the northern Great Plains, including Kansas, Nebraska, Iowa, Minnesota, and Wisconsin, as well as the Desert Southwest. It generally consists of sandy, shallow marine or beach deposits with marine-influenced mudflat sediments, and occasional stream deposits.[8][9]

  1. ^ "Geologic Unit: Woodbury". National Geologic Database. Geolex — Significant Publications. United States Geological Survey. Retrieved November 27, 2020.
  2. ^ Cite error: The named reference AZtoOK was invoked but never defined (see the help page).
  3. ^ Edward Murphy, editor, North Dakota Stratigraphic Column, North Dakota Geological Surve.
  4. ^ a b Cite error: The named reference GeolexDakota was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Ludvigson2010 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference meekandhayden1862 was invoked but never defined (see the help page).
  7. ^ Monroe, James S. and Wicander, Reed (1997) The Changing Earth: Exploring Geology and Evolution (2nd edition) Wadsworth Publishing Company, Belmont, California, page 610, ISBN 0-314-09577-2
  8. ^ "Geology of the Quarry: Dakota Sandstone" Dinosaur National Monument, National Park Service
  9. ^ McLaughlin, Thad G. (1942) "Water-bearing Formations, continued: Cretaceous System: Dakota Group" Geology and Ground-Water Resources of Morton County, Kansas