View source for Earth:Sheep Pen Sandstone

{{Short description|Geologic formation in New Mexico}}
{{Infobox rockunit
| name           = Sheep Pen Sandstone
| image          =
| caption        =
| type           = Formation
| age            = {{Geological range|Norian}}
| period         = late Triassic
| prilithology   = [[Earth:Sandstone|Sandstone]]
| otherlithology =
| namedfor       = Sheep Pen Canyon
| namedby        = B.H. Parker
| year_ts        = 1930
| region         = Colorado<br/>New Mexico<br/>Oklahoma
| country        = {{wipe|United States}}
| coordinates    = {{coord|36.9714|N|103.1743|W|display:inline}}
| unitof         = Dockum Group
| subunits       =
| underlies      = Exeter Sandstone
| overlies       = Sloan Canyon Formation
| thickness      = {{convert|33|meters|feet}}
| extent         =
| area           =
| map            = {{Location map+ | United States#New Mexico
| relief = 1
| width   = 250
| float   = center
| places  =
  {{Location map~ | United States#New Mexico
  | lat_deg = 36.9714
  | lon_deg = -103.1743
  | mark = Purple pog.svg
  | marksize = 12
  }}
}}
| map_caption    =
}}

The '''Sheep Pen Sandstone''' is a [[Earth:Late Triassic|late Triassic]] geologic formation exposed in northeastern New Mexico.<ref name="baldwin-muehlberger-1959">{{cite journal |last1=Baldwin |first1=Brewster |last2=Muehlberger |first2=W.R. |year=1959 |title=Geologic studies of Union County, New Mexico |journal=New Mexico Bureau of Mines and Mineral Resources Bulletin |volume=63 |number=2 |url=https://geoinfo.nmt.edu/publications/monographs/bulletins/downloads/63/Bulletin63.pdf |accessdate=1 September 2020}}</ref> Fossil theropod tracks have been reported from the formation.<ref name="dinosaurdistribution">{{cite book |editor1-last=Weishampel |editor1-first=David B. |editor2-last=Dodson |editor2-first=Peter |editor3-last=Osmólska |editor3-first=Halszka |title=The Dinosauria |date=6 November 2004 |edition=2nd |location=Berkeley |publisher=University of California Press |isbn=0-520-24209-2 |chapter=Dinosaur distribution |pages=517-607}}</ref>

==Description==
The formation consists of up to {{convert|33|meters|feet}} of thinly bedded light brown [[Earth:Sandstone|sandstone]]. It with a slight [[Earth:Angular unconformity|angular unconformity]] on the Sloan Canyon Formation and is overlain [[Earth:Unconformity|unconformably]] by the Exeter Sandstone.<ref name="zeigler-etal-2019">{{cite journal |last1=Ziegler |first1=Kate E. |last2=Ramos |first2=Frank C. |last3=Zimmerer |first3=Matthew J. |title=Geology of Northeastern New Mexico, union and Colfax Counties, New Mexico: A Geologic Summary |journal=New Mexico Geological Society Field Conference Series |date=2019 |volume=70 |issue=4 |pages=47–54 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/70/70_p0047_p0054.pdf |accessdate=1 September 2020}}</ref>

The formation is usually assigned to the Dockum Group.<ref name="baldwin-muehlberger-1959"/><ref name="zeigler-etal-2019"/> The proposal of Spencer G. Lucas and his collaborators to abandon the Dockum Group, possibly in favor of the Chinle Group, is highly controversial.<ref name="lehman-1994">{{cite journal |last1=Lehman |first1=T.M. |year=1994 |title=The saga of the Dockum Group and the case of the Texas/New Mexico boundary fault |journal=New Mexico Bureau of Mines & Mineral Resources Bulletin |volume=150 |pages=37–51 |url=https://geoinfo.nmt.edu/publications/monographs/bulletins/downloads/150/B150.pdf |accessdate=1 September 2020}}</ref>

==Fossils==
Ichnofossils (track fossils) have been found in thee different locations {{convert|10|km|miles}} north of Kenton, Oklahoma. The lower site includes the invertebrates ''Scoyenia'' and the dinosauroid ''Grallator'' on a scour surface. The traces are numerous but of low diversity. The middle site has at least ten distinct trackways, eight of ''Grallator'' and two of ''[[Biology:Brachychirotherium|Brachychirotherium]]''. The upper site has well-preserved tracks of ''Grallator'' and some poorly preserved tracks, possibly of ''Brachychirotherium''. The tracks suggest a stable [[Earth:Ecosystem|ecosystem]] with low diversity, which may be typical of the middle Norian.<ref name="conrad-etal-1987">{{cite journal |last1=Conrad |first1=Kelly |last2=Lockley |first2=Martin G. |last3=Prince |first3=Nancy K. |year=1987 |pages=127–138 |title=Triassic and Jurassic vertebrate-dominated trace fossil assemblages of the Cimarron Valley region--Implications for paleoecology and biostratigraphy |journal=New Mexico Geological Society Field Conference Series |volume=38 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/38/38_p0127_p0138.pdf |accessdate=1 September 2020}}</ref>

==Economic geology==
The formation has some [[Chemistry:Copper|copper]] mineralization around the western Oklahoma panhandle. Some 200 mines were in operation from 1884 to 1925. but these likely produced less than 10,000 tons of ore. The ore took the form of [[Chemistry:Chalcocite|chalcocite]], [[Chemistry:Malachite|malachite]], and [[Chemistry:Azurite|azurite]], deposited both in lenticular beds and in [[Earth:Clastic dike|clastic plug]]s.<ref name="fay-1983">{{cite journal |last1=Fay |first1=Robert O. |title=Copper Deposits in Sheep Pen Sandstone (Triassic) in Cimarron County, Oklahoma, and Adjacent Parts of Colorado and New Mexico |journal=Oklahoma Geological Survey Circular |date=1983 |volume=86 |url=http://www.ogs.ou.edu/pubsscanned/Circulars/circular86mm.pdf}}</ref>

==History of investigation==
The formation was first named by B.H. Parker in 1930.<ref name="parker-1930">{{cite journal |last1=Parker |first1=B.H. |title=Note on occurrence of clastic plugs and dikes in the Cimarron Valley area of Union County, New Mexico |journal=Kansas Geological Society Guidebook for the Annual Field Conference |date=September 1–6, 1930 |volume=4 |pages=131–136}}</ref>

==See also==
* List of fossiliferous stratigraphic units in Colorado
* Paleontology in Colorado

==References==
{{Reflist}}


[[Category:Sandstone formations of the United States]]

{{Sourceattribution|Sheep Pen Sandstone}}