The Mineral Fork Formation is a mapped Proterozoic bedrock unit in Utah.
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.
Exposures According to Yonkee et al. (2000), the Mineral Fork is exposed at the following locations in Utah: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. Antelope Island Big Cottonwood Canyon Santaquin-Provo
And also: Little Cottonwood Canyon
Fossils Abundant microfossils of planktonic alga of Bavlinella faveolata.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.
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.
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