View source for Mancos Shale

{{Short description|Late Cretaceous geologic formation of the Western United States}}
{{Infobox rockunit
| name           = Mancos Shale
| image          = Mancos Shale at type.jpg
| caption        = Mancos Shale at its type location just north of Mancos, Colorado
| type           = [[Geologic formation]]
| age            = [[Albian|Mid Albian]]-[[Campanian]]<br />~{{Fossil range|110|80}}
| period         = Turonian
| prilithology   = [[Shale]]
| otherlithology =
| namedfor       = [[Mancos, Colorado]]
| namedby        =
| region         = [[Arizona]], [[Colorado]], [[New Mexico]], [[Utah]], [[Wyoming]]
| country        = {{USA}}
| coordinates    = {{coord|37.353|N|108.297|W|display:inline}}
| unitof         =
| subunits       = [[Mancos Shale#Subunits|See text]]
| underlies      = [[Mesaverde Formation]]
| overlies       = [[Dakota Group]]
| thickness      =
| extent         = [[Basin and Range Province|Basin and Range]], [[Colorado Plateau]] & [[San Juan Mountains|San Juan Mountains Province]]s
| area           =
| map            ={{Location map+ | United States#Colorado
| relief = 1
| width   = 250
| float   = center
| places  =
  {{Location map~ | United States#Colorado
  | lat_deg = 37.353
  | lon_deg = -108.297
  | mark = Lightgreen pog.svg
  | marksize = 12
  }}
}}
| map_caption    =
}}
The '''Mancos Shale''' or '''Mancos Group''' is a [[Late Cretaceous]] (Upper Cretaceous) [[Formation (stratigraphy)|geologic formation]] of the [[Western United States]].

The Mancos Shale was first described by Cross and Purington in 1899<ref name=CrossPurington>{{cite book |last1=Cross |first1=C.W. |author-link1=Charles Whitman Cross |last2=Purington |first2=C. W. |year=1899 |chapter=Description of the Telluride quadrangle, Colorado |title=United States Geological Survey Atlas |volume=57}}</ref> and was named for exposures near the town of [[Mancos, Colorado]].

==Geology==
[[File:Uinta Piceance Basin stratigraphic column.gif|thumb|left|upright=1.2|[[Stratigraphic column]] showing the relationship of the Mancos and Mowry shales]]
The unit is dominated by [[mudrock]] that accumulated in offshore and marine environments of the Cretaceous [[Western Interior Seaway|North American Inland Sea]].  The Mancos was deposited during the [[Cenomanian]] (locally [[Albian]]) through [[Campanian]] [[Age (geology)|ages]], approximately from 95 million years ago ([[Ma (unit)|Ma]]) to 80 Ma.

[[Stratigraphy|Stratigraphically]] the Mancos Shale fills the interval between the [[Dakota Group|Dakota]] and the [[Mesaverde Formation|Mesaverde]] Group.<ref>{{cite journal |last1=Weimar |first1=R.J. |title=Upper Cretaceous Stratigraphy, Rocky Mountain Area |journal=AAPG Bulletin |date=1960 |volume=44 |pages=1–20 |doi=10.1306/0BDA5F6F-16BD-11D7-8645000102C1865D}}</ref>

The lower marine Mancos Shale conformably [[intertongues]] with terrestrial [[sandstone]]s and mudstones of the Dakota and in its upper part grades into and intertongues with the Mesaverde Group. The shale tongues typically have sharp basal contacts and gradational upper contacts. Whereas in the plains east of the Rocky Mountains certain mappable marine shales are identified as formations (e.g., [[Skull Creek Shale|Skull Creek]], [[Graneros Shale|Graneros]]), correlated deposits within the distribution of the Mancos are named as tongues of the greater Mancos Formation.

Thus, the classification broadly corresponds with the [[Colorado Group]] classification of the [[Great Plains]] region. As such, various units of the Colorado Group are recognized within the Mancos in those areas where their distinct facies can be recognized.<ref name=Rankin>{{cite journal |first1= Charles H. |last1=Rankin |year=1944 |title= Stratigraphy of the Colorado Group, Upper Cretaceous, in Northern New Mexico |journal= New Mexico Bureau of Mines and Mineral Resources Bulletins |issue= 20 |publisher= New Mexico School of Mines |url= https://geoinfo.nmt.edu/publications/monographs/bulletins/downloads/20/Bulletin020.pdf |page= 5 |access-date= 2018-08-13 |quote= ...that all divisions of the Colorado group (Mancos shale) as described in southern Colorado, except the Fort Hays limestone and the Apishapa shale, can be recognized in northern New Mexico. }}</ref>
{{clear left}}
==Occurrences==
[[File:Mancos Mowry shale oil gas fields.png|thumb|right|Mancos Shale and [[Mowry Shale]] oil and gas fields within the [[Uinta Basin]] and [[Piceance Basin]]]]
[[File:Mancos Shale badlands in Capitol Reef NP.jpg|thumb|Mancos Shale badlands in [[Capitol Reef National Park]], southern Utah.]]
The Mancos occurs in the [[Basin and Range Province]], the [[Colorado Plateau|Colorado Plateau Province]], and the [[San Juan Mountains|San Juan Mountains Province]].

===Structural basins===
The Mancos is a diverse unit, with dozens of named subunits in different [[structural basin]]s that often [[Intertongues|intertongue]] with other formations.<ref name="USGS-Strat">[http://3dparks.wr.usgs.gov/coloradoplateau/lexicon/mancos.htm "Colorado River Basin Stratigraphy: Mancos Shale"] United States Geological Survey</ref> The subunits and intertonguing formations (in italics) in each basin, in stratigraphic order, are:

{|
|- style="vertical-align: top;"
|
* Black Mesa Basin<ref>{{cite journal |last1=Kirkland |first1=J.I. |year=1991 |title=Lithostratigraphic and biostratigraphic framework for the Mancos Shale (Late Cenomanian to Middle Turonian) |journal=Geological Society of America Special Paper |volume=260 |page=88 |isbn=978-0-8137-2260-3 |url=https://books.google.com/books?id=Ymn0oyhfBmwC&q=mancos+%22black+mesa+basin%22&pg=PA88 |access-date=16 September 2021}}</ref>
::Upper shale member
::Hopi Sandy Member
::Middle shale member
::Lower shale member
* [[Chama Basin]]<ref>{{cite journal |last1=Landis |first1=E.R. |last2=Dane |first2=C.H. |year=1967 |title=Geologic map of the Tierra Amarilla quadrangle, Rio Arriba County, New Mexico, with description |journal=New Mexico Bureau of Mines and Mineral Resources Geologic Map |volume=19 |url=https://ngmdb.usgs.gov/Prodesc/proddesc_73099.htm |access-date=17 September 2021}}</ref>
::Upper shale unite
::El Vado Sandstone Member
::Middle shale unit
::Cooper Arroyo Sandstone Member
::[[Juana Lopez Member]]
::Lower shale unit
::[[Greenhorn Limestone]]
::[[Graneros Shale]]
* [[Estancia Basin]] (Mancos Group)<ref>{{cite journal |last1=Lisenbee |first1=Alvis |last2=Maynard |first2=Steve |title=Geologic Map of the Captain Davis Mountain Quadrangle, Santa Fe County, New Mexico |journal=New Mexico Bureau of Geology and Mineral Resources Open-file Digital Geologic Map |date=May 2001 |volume=OF-GM 48 |url=https://geoinfo.nmt.edu/publications/maps/geologic/ofgm/downloads/48/OFGM-48_CaptainDavisMountainReport.pdf |access-date=16 September 2021}}</ref>
::[[Niobrara Formation]]
::[[Carlile Shale]]
::Greenhorn Limestone
|
* [[Paradox Basin]]<ref name=NuccioCondon>{{cite journal |last1=Nuccio |first1=Vito F. |last2=Condon |first2=Stephen M. |title=Burial and thermal history of the Paradox Basin, Utah and Colorado, and petroleum potential of the Middle Pennsylvanian Paradox Basin |journal=United States Geological Survey Bulletin |date=1996 |volume=2000-O |doi=10.3133/b00O |page=O6|url=https://digital.library.unt.edu/ark:/67531/metadc304484/ }}</ref>
:: West and northwest
:::[[Masuk Formation|Masuk Member]]
:::Emery Sandstone
:::Blue Gate Shale
:::[[Ferron Sandstone]]
:::Tununk Shale
:: North
:::Buck Tongue
:::''[[Castlegate Sandstone]]''
:::Juana Lopez Member
:: Northeast and east
:::Juana Lopez Member
:::Greenhorn Limestone
* [[Piceance Basin]]
::Buck Tongue<ref name=FisherEtal>{{cite journal |last1=Fisher |first1=D.J. |last2=Erdmann |first2=C.E. |last3=Reeside |first3=J.B. Jr. |title=Cretaceous and Tertiary formations of the Book Cliffs, Carbon, Emery, and Grand Counties, Utah, and Garfield and Mesa Counties, Colorado |journal=United States Geological Survey Professional Paper |series=Professional Paper |date=1960 |volume=332 |doi=10.3133/pp332|doi-access=free }}</ref><ref>{{cite journal |last1= Johnson |first1=S.Y. |last2=Johnson |first2=R.C. |year=1991 |title=Stratigraphic and time-stratigraphic cross sections of Phanerozoic rocks along line A-A', Uinta and Piceance basin area-Eagle basin, Colorado, to eastern Basin-and-Range area, Utah |journal=U.S. Geological Survey Miscellaneous Investigations Series Map |volume=I-2184-A |url=https://ngmdb.usgs.gov/Prodesc/proddesc_10174.htm |access-date=15 September 2021}}</ref>
:: Anchor Mine Tongue<ref name=Franczyk>{{cite journal |last1=Franczyk |first1=Karen J. |title=Depositional controls on the late Campanian Sego Sandstone and implications for associated coal-forming environments in the Uinta and Piceance basins |journal=United States Geological Survey Bulletin |date=1989 |volume=1787-F |doi=10.3133/b1787F|doi-access=free }}</ref>
:: Main body
|
* [[San Juan Basin]]<ref>{{cite journal |last1=Dane |first1=C.H. |year=1948 |title=Geology and oil possibilites of the eastern side of the San Juan basin, Rio Arriba County, New Mexico |journal=U.S. Geological Survey Oil and Gas Investigations Map |volume=OM-78 |url=https://ngmdb.usgs.gov/Prodesc/proddesc_5439.htm |access-date=16 September 2021}}</ref><ref name=newmex>{{cite journal |last1=Owen |first1=Donald E. |last2=Forgas |first2=Angelique M. |last3=Miller |first3=Shawn A. |last4=Stelly |first4=Ryan J. |last5=Owen |first5=Donald E. Jr. |title=Surface and subsurface stratigraphy of the Burro Canyon Formation, Dakota Sandstone, and intertongued Mancos Shale of the Chama Basin, New Mexico |year=2005 |journal=New Mexico Geological Society Field Conference Series |volume=56 |pages=218–226 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/56/56_p0218_p0226.pdf |access-date=15 September 2021}}</ref>
::Mulatto Tongue<ref>{{cite journal |last1=O'Sullivan |first1=R.B. |last2=Repenning |first2=C.A. |last3=Beaumont |first3=E.C. |last4=Page |first4=H.G. |title=Stratigraphy of the Cretaceous rocks and the Tertiary Ojo Alamo Sandstone, Navajo and Hopi Indian Reservations, Arizona, New Mexico, and Utah |journal=United States Geological Survey Professional Paper |series=Professional Paper |date=1972 |volume=521-E |doi=10.3133/pp521E|doi-access=free }}</ref>
::''Dilco Coal Member of [[Crevasse Canyon Formation]]''
::Niobrara Calcareous Shale
::Carlile Shale
::Greenhorn Limestone
::[[Graneros Shale]]<ref name=Rankin/>
:: ''Paguate Tongue of Dakota Formation''
:: Clay Mesa Tongue<ref>{{cite journal |last1=Landis |first1=Edwin R. |last2=Dane |first2=C.H. |last3=Cobban |first3=William Aubrey |title=Stratigraphic terminology of the Dakota Sandstone and Mancos Shale, west-central New Mexico |journal=United States Geological Survey Bulletin |date=1973 |volume=1372-J |doi=10.3133/b1372J|doi-access=free }}</ref>
* Socorro Basin<ref>{{cite journal |last1=Hook |first1=Steven C. |title=Contributions to mid-Cretaceous paleontology and stratigraphy of New Mexico — part II |journal=New Mexico Bureau of Mines & Mineral Resources Circular |date=1983 |volume=185 |pages=15–16 |url=https://geoinfo.nmt.edu/publications/monographs/circulars/downloads/185/Circular-185.pdf |access-date=17 September 2021}}</ref>
:: D-Cross Tongue
:: ''[[Gallup Sandstone]]''
:: Pescado Tongue
:: ''[[Tres Hermanos Formation]]''
:: Rio Salado Tongue
:: ''Twowells Tongue of Dakota Formation''
:: Whitewater Arroyo Tongue
|
* [[Uintah Basin]]<ref>{{cite journal |last1=Walton |first1=P.T. |year=1944 |title=Geology of the Cretaceous of the Uinta basin, Utah |journal=Bulletin of the Geological Society of America |volume=55 |number=1 |pages=91–130|doi=10.1130/GSAB-55-91 |bibcode=1944GSAB...55...91W }}</ref>
:: Anchor Mine Tongue<ref name=Franczyk/>
:: ''[[Sego Sandstone]]''
:: Upper shale member
:: [[Frontier Sandstone]]
:: Middle shale member
:: [[Aspen Shale]]
:: Lower shale member
:: [[Mowry Shale]]<ref>{{cite journal |last1=Molenaar |first1=Cornelius M. |last2=Wilson |first2=B.W. |title=The Frontier Formation and associated rocks of northeastern Utah and northwestern Colorado |journal=United States Geological Survey Bulletin |date=1990 |volume=1787-M |doi=10.3133/b1787M|url=https://digital.library.unt.edu/ark:/67531/metadc304453/ |doi-access=free }}</ref>
|}

==History of investigation==
{{wide image|Mancos Shale at Mesa Butte.jpg|x160px|Tununk Member of the Mancos Shale below the capping Ferron Sandstone Member. West side of the San Rafael Swell, Emery County, Utah.|33%}}
The Mancos Shale was first named by [[Charles Whitman Cross]] and C.W. Purington in 1899, for outcrops near the town of [[Mancos, Colorado]] and along the [[Mancos River]] nearby. The two geologists also traced the unit into the [[Telluride, Colorado]] area.<ref name=CrossPurington/> W.T. Lee had traced the unit north into the [[Grand Mesa]] area, defining it as all marine shale between the Dakota and the Mesaverde.<ref>{{cite journal |last1=Lee |first1=Willis Thomson |title=Coal fields of Grand Mesa and the West Elk Mountains, Colorado |journal=United States Geological Survey Bulletin |date=1912 |volume=510 |doi=10.3133/b510|hdl=2346/65145 |hdl-access=free }}</ref> It was subsequently traced into Utah<ref>{{cite journal |last1=Lupton |first1=C.T. |title=Oil and gas near Green River, Grand County, Utah |journal=United States Geological Survey Bulletin |date=1914 |volume=541-D |doi=10.3133/b541D|doi-access=free }}</ref> and New Mexico.<ref>{{cite journal |last1=Reeside |first1=John B. Jr. |last2=Knowlton |first2=F.H. |title=Professional Paper |journal=United States Geological Survey Professional Paper |date=1924 |volume=134 |doi=10.3133/pp134|doi-access=free }}</ref>

During their work in New Mexico in 1924, J.B. Reeside, Jr., and F.H. Knowlton found that the Mancos Shale could be divided into [[biostratigraphic]] layers corresponding closely to formations of the [[Colorado Group]] further east. By 1944, Rankin had concluded that most of the formations of the Colorado Group could be identified as [[lithostratigraphic]] members of the Mancos Shale as well.<ref name=Rankin/> The unit was raised to [[Group (stratigraphy)|group rank]] by C.E. Jamison in 1911,<ref>{{cite journal |last1=Jamison |first1=C.E. |year=1911 |title=Geology and Mineral Resources of a Portion of Fremont County, Wyo |journal=Wyoming Geological Survey Bulletin|volume=2B |url=https://books.google.com/books?id=Zz0QAAAAIAAJ&q=%22mancos+group%22&pg=PP7 |access-date=21 September 2021}}</ref> and is sometimes given group rank in New Mexico<ref>{{cite book |last1=Zakis |first1=William |chapter=Table Mesa Oil Field San Juan County, New Mexico |title= Geological Symposium of the Four Corners Region |year=1952 |url=https://archives.datapages.com/data/fcgs/data/001/001001/86_four-corners010086.htm |access-date=21 September 2021}}</ref> and Utah<ref>{{cite journal |last1=Roberto |first1=Sarmiento |title=Microfossil Zonation of Mancos Group |journal=AAPG Bulletin |date=1957 |volume=41 |doi=10.1306/0BDA5927-16BD-11D7-8645000102C1865D}}</ref> as well.

==See also==
{{Portal|Paleontology|Earth sciences}}
* [[List of fossiliferous stratigraphic units in Arizona]]
* [[List of fossiliferous stratigraphic units in Colorado]]
* [[List of fossiliferous stratigraphic units in New Mexico]]
* [[List of fossiliferous stratigraphic units in Utah]]
* [[List of fossiliferous stratigraphic units in Wyoming]]

==References==
{{reflist|22em}}

{{Chronostratigraphy of Colorado|Mesozoic state=expanded}}

[[Category:Shale formations of the United States]]
[[Category:Upper Cretaceous Series of North America]]
[[Category:Cretaceous United States]]
[[Category:Campanian Stage]]
[[Category:Cenomanian Stage]]
[[Category:Coniacian Stage]]
[[Category:Santonian Stage]]
[[Category:Turonian Stage]]
[[Category:Cretaceous Arizona]]
[[Category:Cretaceous Colorado]]
[[Category:Cretaceous formations of New Mexico]]
[[Category:Cretaceous geology of Texas]]
[[Category:Cretaceous geology of Utah]]
[[Category:Cretaceous geology of Wyoming]]
[[Category:Geology of the Rocky Mountains]]