Mineral Fork Formation
The Mineral Fork Formation is a mapped Proterozoic bedrock unit in Utah.
| Mineral Fork Formation Stratigraphic range: Proterozoic | |
|---|---|
 Boulder of diamictite of the Mineral Fork Formation, along the Elephant Head Trail, Antelope Island, Utah. | |
| Type | sedimentary |
| Underlies | Mutual Formation (Big Cottonwood Canyon), Tintic Formation (Santaquin-Provo), or Kelly Canyon Formation (Antelope Island)[1] |
| Overlies | Farmington Canyon Complex (Antelope Island), Big Cottonwood Formation (other locations)[1] |
| Thickness | 1000 to 3000 feet |
| Lithology | |
| Primary | Tillite, Shale, Quartzite, Conglomerate |
| Location | |
| Region | Southern Rocky Mountains |
| Extent | Wasatch Mountains, Antelope Island |
| Type section | |
| Named for | Mineral Fork, Salt Lake County, Utah |
| Named by | Granger et al., 1952[2] |
Description
Granger et al. (1952) describe the Mineral Fork Formation as black tillite consisting of boulders, cobbles and pebbles of quartzite, limestone, or granitic rocks in a black sandy matrix, with dark-gray to black varved slate or shale, dark-gray quartzite, and occasional channel fillings of boulder conglomerate.[2]
Exposures
According to Yonkee et al. (2000), the Mineral Fork is exposed at the following locations in Utah:[1]
And also:
Fossils
Abundant microfossils of planktonic alga of Bavlinella faveolata.[3]
Age
The presence of Bavlinella faveolata in the formation indicates a likely age of 750–650 Ma, because this fossil occurs elsewhere where it is well-dated radiometrically. The Mineral Fork Formation is no older than 1,250 Ma and no younger than 540 Ma. Thus it is likely Neoproterozoic but possibly Mesoproterozoic.[3]
References
- Yonkee, W.A, Willis, G.C., and Doelling, H.H., 2000, Proterozoic and Cambrian Sedimentary and Low-grade Metasedimentary Rocks on Antelope Island, in The Geology of Antelope Island, Davis County, Utah, eds. J.K. King and G.C. Willis, Utah Geological Survey, p. 37–47.
- Granger, A.E., Calkins, F.C., Crittenden, M.D., Jr., and Sharp, B.J., 1952, Geology of the Wasatch Mountains east of Salt Lake City, IN Marcel, R.E., ed., Geology of the central Wasatch Mountains, Utah: Utah Geological Society, Guidebook to the geology of Utah, no. 8, p. 1-37.
- Knoll, A.H., Blick, N., and Awramik, S.M., 1981, Stratigraphic and ecologic implications of late Precambrian microfossils from Utah: American Journal of Science, v. 281, no. 3, p. 247-263.