Spearfish Formation
| Spearfish Formation | |
|---|---|
Piper Formation | |
| Overlies | Minnekahta Limestone |
| Thickness | 350–800 feet (110–240 m)[1] |
| Lithology | |
| Primary | Siltstone, sandstone |
| Other | Shale |
| Location | |
| Region | Black Hills and nearby states |
| Country | United States |
| Type section | |
| Named for | Spearfish, South Dakota |
| Named by | Darton, 1899 |
The Spearfish Formation is a geologic
claystone, conglomerate, dolomite, and oil shale.[4] It is typically regarded as Permian–Triassic in age,[4] although its original description[5] included Jurassic rocks.[6]
The Spearfish Formation is interpreted as representing shallow marine to coastal terrestrial deposition, like the modern
hypersaline waters (limestone), hypersaline microbial mats (oil shale), and sabkhas (dolomite). The marine waters of the shallow continental sea retreated during the deposition of the formation, reflected in a change from dominantly nearshore marine to coastal terrestrial deposition over time.[4]
The Spearfish Formation is sparsely fossiliferous. So far, only
bivalves, and trace fossils have been found.[4]
References
- ^ Driscoll, D.G.; Cater J.M.; Williamson J.E.; Putnam L.D. (2002). "Hydrology of the Black Hills Area, South Dakota" (PDF). USGS. pp. 11–15. Retrieved 29 December 2012.
- ^ United States Geological Survey. "Geologic Unit: Spearfish". GEOLEX database. USGS. Retrieved 29 December 2012.
- ^ Karner, F. R. and R. L. Patelke. 1989. General geology of the Black Hills and Bear Lodge Mountains. Pages 7-20 in Karner, F. R., editor. Volcanism and plutonism of Western North America: Devils Tower-Black Hills alkalic igneous rocks and general geology. Field trip T131 in Hanshaw, P. M., editor. Field trips for the 28th international geological congress. American Geophysical Union, Washington, DC.
- ^ a b c d Sabel, J. M. 1984. Sedimentology and depositional history of the Permo-Triassic Spearfish Formation, southwestern Black Hills, South Dakota. Pages 295-307 in Goolsby, J. and D. Morton, editors. The Permian and Pennsylvanian geology of Wyoming. Wyoming Geological Association, Casper, WY. Guidebook 35.
- ^ Darton, N. H. 1899. Jurassic formations of the Black Hills of South Dakota. Geological Society of America Bulletin 10:383-396.
- ^ Richardson, G. B. 1903. The upper red beds of the Black Hills. Journal of Geology 11:365-393.
- ^ Sabel, J. M. 1983. Sedimentology of Spearfish Formation. AAPG Bulletin 67(3):543-544.