GEOLOGIC MAP OF THE PROVO 30' X 60' QUADRANGLE, UTAH, WASATCH, AND SALT LAKE COUNTIES, UTAH

The Provo 30' x 60' quadrangle lies along the populous Wasatch Front in north-central Utah and covers parts of the eastern Great Basin, Middle Rocky Mountains, and western Uinta Basin. This geologic map (1:62,500 scale) updates interim work from 2011. Precambrian basement rocks are not exposed but overlying strata include Neoproterozoic to Tertiary cover rocks. A package of relatively thicker Neoproterozoic, Paleozoic, and Mesozoic sedimentary rocks was translated eastward as part of the Charleston-Nebo (Provo) salient of the Sevier fold-thrust belt (Early Cretaceous to Eocene contractional tectonism). A thinner package of similar age includes footwall rocks east and north of the thrust system. Key structural features include multiple thrust sheets, the Santaquin culmination, the Charleston transverse zone, and a salient-frontal triangle zone. The welt of Sevier belt rocks later underwent extensional collapse from about 36 to 20 Ma. This extension occurred via reactivation of the sole thrust, preexisting thrusts that cut the Charleston-Nebo hanging wall, and bedding plane detachments. Local basin infilling and accompanying calc-alkaline volcanism (~38 to 30 Ma) were synchronous with the late Eocene to Oligocene extension. Much of the eastern part of the map area is covered by Tertiary strata (Green River, Uinta, and associated formations) deposited in the Laramide Uinta Basin. Later extensional tectonism created the basin-and-range topography of the western area from about 20 Ma to the present; Utah Valley contains up to 4500 m of basin fill. Quaternary deposits are from lacustrine and deltaic (Lake Bonneville), glacial, alluvial, spring, mass-movement, and mixed environments. Continued extension creates seismic risk on the Provo segment of the Wasatch fault zone, East Cedar Valley fault zone, Utah Lake faults, and Strawberry Valley faults. We compiled and obtained new data on subsurface materials, geochronology, paleontology, and geochemistry. This map provides insights into the complex geologic history, as well as the geologic hazards and resources of this area.