The geology of Utah, in the western United States, includes rocks formed at the edge of the proto-North American continent during the Precambrian.
A shallow marine sedimentary environment covered the region for much of the Paleozoic and Mesozoic, followed by dryland conditions, volcanism, and the formation of the basin and range terrain in the Cenozoic.
Prior to the 1960s, geologists inferred the Vishnu and Farmington Canyon gneiss and schist as Archean in age, but subsequent research indicated a formation between 1.6 and 1.5 billion years ago in the Proterozoic.
Marine deposition was continuous, with numerous fossils in an unbroken record, such as the crinoid stems, brachiopods, and corals in the Chainman-Manning Canyon Shale.
A major marine transgression generated the Kaibab Limestone (the rimrock of the Grand Canyon), represented by the Park City and Phosphoria groups in Utah.
The early-Triassic Moenkopi Formation is a mudstone with thin layers of limestone formed as the sea spread out across mud flats and hosts the Canyonlands in southern Utah.
The thickest Jurassic sediments are between Devil's Slide, east of Ogden and Marysvale, which include gypsum and other evaporites, mined from the Arapien Shale.
In the Wasatch Plateau, the Ferron Sandstone represents a brief marine regression to the east and serves as an important natural gas horizon.
Paleocene Lake Flagstaff left algal limestone in the Southern Wasatch Mountains, along with marl-mudstone in Bryce Canyon, Cedar Breaks, and Richfield.
An abrupt shift to volcanic activity in the Needle Range and at Marysvale, Crystal Peak, Tintic, and Bingham took place in the Oligocene, erupting with thick ash flow tuff and producing welded ignimbrite.
The Needle Range ash flow tuff is the most extensive, covering 13,000 square miles in southwest Utah and eastern Nevada.
Volcanism was related to the subducting Farallon Plate and took place from 35 to 19 million years ago, predating the block faulting of the Basin and Range Province, making tuff useful for stratigraphic comparisons.
Volcanic activity lessened from 19 to 16 million years ago, followed by basalt flows, cinder cones, and the Topaz-Spor Mountain rhyolite into the Miocene, Pliocene, and Quaternary.
This mountain belt formed from 50–160– million years ago due to subduction of the Farallon oceanic crust under the North American Plate.