Geologic map of the Grayback Hills quadrangle, Tooele County, Utah (M-166)

By: H. H. Doelling, B. J. Solomon, and S. F. Davies

The Grayback Hills quadrangle lies along the eastern margin of the Great Salt Lake Desert in northwestern Utah about 80 miles west of Salt Lake City. Exposed rocks are Permian and Triassic strata, Tertiary lava and volcaniclastic rocks, and Quaternary deposits of late Pleistocene and Holocene age. Permian rocks are assigned to the Grandeur? Formation, Murdock Mountain Formation, and Gerster Formation. Exposed Triassic rocks are assigned to the Dinwoody? Formation and Thaynes Formation. Upper Early Triassic (Smithian and Spathian) conodonts and ammonites have been identified in the Thaynes Formation. Tertiary rocks consist of a unit of tuffaceous sandstone, conglomerate, dacite, and a trachyandesite unit. The trachyandesite lava is above the volcaniclastic rocks, but may also be interlayered with them.

Other Information:
Published: 1995
Pages: 22 p.
Plates: 2 pl.
Scale: 1:24,000
Location: Tooele County
Media Type: Paper Map