|Sheep Pen Sandstone|
Stratigraphic range: late Triassic
|Unit of||Dockum Group|
|Overlies||Sloan Canyon Formation|
|Thickness||33 meters (108 ft)|
|Named for||Sheep Pen Canyon|
|Named by||B.H. Parker|
The formation consists of up to 33 meters (108 ft) of thinly bedded light brown sandstone. It with a slight angular unconformity on the Sloan Canyon Formation and is overlain unconformably by the Exeter Sandstone.
The formation is usually assigned to the Dockum Group. The proposal of Spencer G. Lucas and his collaborators to abandon the Dockum Group, possibly in favor of the Chinle Group, is highly controversial.
Ichnofossils (track fossils) have been found in thee different locations 10 kilometres (6.2 mi) 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 Brachychirotherium. The upper site has well-preserved tracks of Grallator and some poorly preserved tracks, possibly of Brachychirotherium. The tracks suggest a stable ecosystem with low diversity, which may be typical of the middle Norian.
The formation has some 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 chalcocite, malachite, and azurite, deposited both in lenticular beds and in clastic plugs.
History of investigation
The formation was first named by B.H. Parker in 1930.
- Baldwin and Muehlberger 1959
- Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
- Ziegler et al. 2019
- Lehman 1994
- Conrad et al. 1987
- Fay 1983
- Parker 1930
- Baldwin, Brewster; Muehlberger, W.R. (1959). "Geologic studies of Union County, New Mexico" (PDF). New Mexico Bureau of Mines and Mineral Resources Bulletin. 63 (2). Retrieved 1 September 2020. CS1 maint: discouraged parameter (link)
- Conrad, Kelly; Lockley, Martin G.; Prince, Nancy K. (1987). "Triassic and Jurassic vertebrate-dominated trace fossil assemblages of the Cimarron Valley region--Implications for paleoecology and biostratigraphy" (PDF). New Mexico Geological Society Field Conference Series. 38: 127–138. Retrieved 1 September 2020. CS1 maint: discouraged parameter (link)
- Fay, Robert O. (1983). "Copper Deposits in Sheep Pen Sandstone (Triassic) in Cimarron County, Oklahoma, and Adjacent Parts of Colorado and New Mexico" (PDF). Oklahoma Geological Survey Circular. 86.
- Lehman, T.M. (1994). "The saga of the Dockum Group and the case of the Texas/New Mexico boundary fault" (PDF). New Mexico Bureau of Mines & Mineral Resources Bulletin. 150: 37–51. Retrieved 1 September 2020. CS1 maint: discouraged parameter (link)
- Parker, B.H. (September 1–6, 1930). "Note on occurrence of clastic plugs and dikes in the Cimarron Valley area of Union County, New Mexico". Kansas Geological Society Guidebook for the Annual Field Conference. 4: 131–136.
- Weishampel, David B.; Dodson, Peter; Osmólska, Halszka, eds. (6 November 2004). The Dinosauria (2nd ed.). Berkeley: University of California Press. ISBN 0-520-24209-2.
- Ziegler, Kate E.; Ramos, Frank C.; Zimmerer, Matthew J. (2019). "Geology of Northeastern New Mexico, union and Colfax Counties, New Mexico: A Geologic Summary" (PDF). New Mexico Geological Society Field Conference Series. 70 (4): 47–54. Retrieved 1 September 2020. CS1 maint: discouraged parameter (link)