Constraining The Provenance Of Middle Cenozoic Fluvial Sandstone In The Central Rocky Mountains Using Detrital Zircon U-pb Geochronology And Sandstone Petrography
Mankin, Alex Leigh
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Detrital zircon U-Pb geochronology and sandstone petrography are studied to constrain the provenance of middle Cenozoic fluvial sandstone in the Central Rocky Mountains. Petrographic point counting of 12 sandstone samples show immature compositions, and combined recycled orogen provenance of the proximal Laramide uplifts and magmatic arc provenance of the distal middle Cenozoic magmatism in western and southwestern North America. A total of 670 detrital zircon U-Pb ages show a 17-44 Ma population, derived from the distal middle Cenozoic magmatism, and populations of 45-218 Ma, 220-708 Ma, 948-1326 Ma, 1332-1816 Ma, and 1825-3314 Ma, derived or recycled from the Precambrian basement cores and the Phanerozoic sedimentary rocks on the flanks of the local Laramide uplifts. Detrital zircon U-Pb geochronology also yield maximum depositional ages between 37.8±1.1 Ma and 27.3±1.1 Ma for seven sandstone samples. These ages are generally consistent with the available radiometric ages of tuff beds and magnetostratigraphic ages.