Dawson Arkose: Difference between revisions
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{{Short description|Geologic formation in the Denver Basin, Colorado, U.S.}} |
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{{Infobox rockunit |
{{Infobox rockunit |
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| name = Dawson Arkose |
| name = Dawson Arkose |
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| type = [[Formation (stratigraphy)|Formation]] |
| type = [[Formation (stratigraphy)|Formation]] |
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| age = Early [[Paleocene]] |
| age = Early [[Paleocene]] |
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| period = Paleocene |
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| prilithology =[[arkose|Arkosic]] [[sandstone]] |
| prilithology =[[arkose|Arkosic]] [[sandstone]] |
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| otherlithology =[[Mudstone]] |
| otherlithology =[[Mudstone]] |
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| namedfor =Dawson Butte |
| namedfor =[[Dawson Butte]] |
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| namedby =Richardson (1915)<ref>Richardson, G.B. 1915. Castle Rock, Colorado. U.S. Geological Survey Atlas Folio 198.</ref> |
| namedby =Richardson (1915)<ref>Richardson, G.B. 1915. Castle Rock, Colorado. U.S. Geological Survey Atlas Folio 198.</ref> |
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| region = [[Colorado]] |
| region = [[Colorado]] |
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}} |
}} |
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The '''Dawson Arkose''' is a [[Formation (geology)|geologic formation]] in the [[Denver Basin]] that underlies the [[Denver]] area in [[Colorado]]. It is characterized by alternating beds of [[arkose|arkosic]] [[sandstone]] and [[mudstone]].<ref name=Raynolds>Raynolds, R.G. 2002. Upper Cretaceous and Tertiary stratigraphy of the Denver Basin, Colorado. Rocky Mountain Geology, vol. 37, no. 2, p. 111-134.</ref> The Dawson Arkose contains plant remains<ref>Johnson, K.R., Reynolds, M.L., Werth, K.W., and Thomasson, J.R. 2003. Overview of the Late Cretaceous, early Paleocene, and early Eocene megafloras of the Denver Basin, Colorado. Rocky Mountain Geology, vol. 38, no. 1, p. 101-120.</ref> and other nonmarine [[fossil]]s, and hosts [[aquifer]]s that are important sources of water for the area.<ref name=Raynolds&Johnson>Raynolds, R.G. and Johnson, K.R. 2003. Synopsis of the stratigraphy and paleontology of the uppermost Cretaceous and lower Tertiary strata in the Denver Basin, Colorado. Rocky Mountain Geology, vol. 38, no. 1, p. 171-181.</ref> |
The '''Dawson Arkose''' is a [[Formation (geology)|geologic formation]] in the [[Denver Basin]] that underlies the [[Denver]] area in [[Colorado]]. It is characterized by alternating beds of [[arkose|arkosic]] [[sandstone]] and [[mudstone]].<ref name=Raynolds>Raynolds, R.G. 2002. Upper Cretaceous and Tertiary stratigraphy of the Denver Basin, Colorado. Rocky Mountain Geology, vol. 37, no. 2, p. 111-134.</ref><ref name=USGS>{{Cite web|url=http://ngmdb.usgs.gov/Geolex/UnitRefs/DawsonRefs_7850.html|title=Geologic Unit: Dawson|author=U.S. Geological Survey| accessdate=2014-12-27}}</ref> The Dawson Arkose contains plant remains<ref>Johnson, K.R., Reynolds, M.L., Werth, K.W., and Thomasson, J.R. 2003. Overview of the Late Cretaceous, early Paleocene, and early Eocene megafloras of the Denver Basin, Colorado. Rocky Mountain Geology, vol. 38, no. 1, p. 101-120.</ref> and other nonmarine [[fossil]]s, and hosts [[aquifer]]s that are important sources of water for the area.<ref name=Raynolds&Johnson>Raynolds, R.G. and Johnson, K.R. 2003. Synopsis of the stratigraphy and paleontology of the uppermost Cretaceous and lower Tertiary strata in the Denver Basin, Colorado. Rocky Mountain Geology, vol. 38, no. 1, p. 171-181.</ref> |
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==Stratigraphy== |
==Stratigraphy== |
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The Dawson Arkose consists of [[alluvial fan]] and [[fluvial]] deposits that accumulated at the foot of the growing Rocky Mountain Front |
The Dawson Arkose consists of [[alluvial fan]] and [[fluvial]] deposits that accumulated at the foot of the growing [[Rocky Mountain Front]] ranges. It overlies and interfingers with the [[Denver Formation]] which spans the [[Cretaceous-Paleogene boundary]], and is of early [[Paleocene]] ([[Puercan]]) age.<ref>Barclay, R.S., Johnson, K.R., Betterton, W.J., and Dilcher, D.L., 2003. Stratigraphy and megaflora of a K-T boundary section in the eastern Denver Basin, Colorado. Rocky Mountain Geology vol. 38, no. 1, p. 45-71.</ref> In 2002 the Dawson Arkose was included as part of a larger unconformity-bounded unit named the D1 Sequence, in order to facilitate basin-wide studies and avoid confusion arising from the lateral and vertical [[facies]] changes that occur within the Denver Basin. The base of the D1 is marked by the abrupt facies change at the top of the [[Laramie Formation]], and its top is placed at the base of a regional [[paleosol]] series. The [[Arapahoe Formation]] and the Denver Formation are also included in the D1 Sequence.<ref name=Raynolds /> |
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==References== |
==References== |
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==See also== |
==See also== |
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{{Portal|Earth sciences|Colorado|Paleontology |
{{Portal|Earth sciences|Colorado|Paleontology}} |
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* [[List of fossiliferous stratigraphic units in Colorado]] |
* [[List of fossiliferous stratigraphic units in Colorado]] |
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* [[Paleontology in Colorado]] |
* [[Paleontology in Colorado]] |
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{{Chronostratigraphy of Colorado|Cenozoic state=expanded}} |
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[[Category:Paleogene stratigraphic units of North America]] |
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[[Category:Geologic formations of Colorado]] |
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[[Category:Geology of the Rocky Mountains]] |
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Latest revision as of 21:17, 28 July 2024
| Dawson Arkose | |
|---|---|
| Stratigraphic range: Early Paleocene | |
| Type | Formation |
| Unit of | D1 Sequence[1] |
| Lithology | |
| Primary | Arkosic sandstone |
| Other | Mudstone |
| Location | |
| Region | Colorado |
| Country | United States |
| Type section | |
| Named for | Dawson Butte |
| Named by | Richardson (1915)[2] |
The Dawson Arkose is a geologic formation in the Denver Basin that underlies the Denver area in Colorado. It is characterized by alternating beds of arkosic sandstone and mudstone.[1][3] The Dawson Arkose contains plant remains[4] and other nonmarine fossils, and hosts aquifers that are important sources of water for the area.[5]
Stratigraphy
[edit]The Dawson Arkose consists of alluvial fan and fluvial deposits that accumulated at the foot of the growing Rocky Mountain Front ranges. It overlies and interfingers with the Denver Formation which spans the Cretaceous-Paleogene boundary, and is of early Paleocene (Puercan) age.[6] In 2002 the Dawson Arkose was included as part of a larger unconformity-bounded unit named the D1 Sequence, in order to facilitate basin-wide studies and avoid confusion arising from the lateral and vertical facies changes that occur within the Denver Basin. The base of the D1 is marked by the abrupt facies change at the top of the Laramie Formation, and its top is placed at the base of a regional paleosol series. The Arapahoe Formation and the Denver Formation are also included in the D1 Sequence.[1]
References
[edit]- ^ a b c Raynolds, R.G. 2002. Upper Cretaceous and Tertiary stratigraphy of the Denver Basin, Colorado. Rocky Mountain Geology, vol. 37, no. 2, p. 111-134.
- ^ Richardson, G.B. 1915. Castle Rock, Colorado. U.S. Geological Survey Atlas Folio 198.
- ^ U.S. Geological Survey. "Geologic Unit: Dawson". Retrieved 2014-12-27.
- ^ Johnson, K.R., Reynolds, M.L., Werth, K.W., and Thomasson, J.R. 2003. Overview of the Late Cretaceous, early Paleocene, and early Eocene megafloras of the Denver Basin, Colorado. Rocky Mountain Geology, vol. 38, no. 1, p. 101-120.
- ^ Raynolds, R.G. and Johnson, K.R. 2003. Synopsis of the stratigraphy and paleontology of the uppermost Cretaceous and lower Tertiary strata in the Denver Basin, Colorado. Rocky Mountain Geology, vol. 38, no. 1, p. 171-181.
- ^ Barclay, R.S., Johnson, K.R., Betterton, W.J., and Dilcher, D.L., 2003. Stratigraphy and megaflora of a K-T boundary section in the eastern Denver Basin, Colorado. Rocky Mountain Geology vol. 38, no. 1, p. 45-71.
