--> Tectonic Uplift of the Wet Mountains and Southern Front Range in the Mesozoic Inferred From Detrital Zircon U-Pb Geochronology of Middle to Upper Jurassic Strata in the Paradox Basin, Western Colorado

AAPG ACE 2018

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Tectonic Uplift of the Wet Mountains and Southern Front Range in the Mesozoic Inferred From Detrital Zircon U-Pb Geochronology of Middle to Upper Jurassic Strata in the Paradox Basin, Western Colorado

Abstract

The Middle to Late Jurassic in the western United States marked a period of active deposition of eolian and fluvio-lacustrine sediments in the Paradox Basin. Provenance from terranes in the southern and eastern Appalachian highlands into Mesozoic sedimentary basins of the western continental interior are well constrained, and the shift from eolian to hypersaline lacustrine ~160Ma is typically attributed to the northern movement of Laurentia during this time accompanied by a more temperate climate. However, new evidence suggests that drainage reorganization played a major part in the shifting depositional environments.

In this study, we present a dataset of 7,887 detrital zircon U-Pb ages from 31 sandstone samples collected from three successive Middle to Late Jurassic units within the Paradox Basin: Entrada Sandstone, Wanakah Formation, and Morrison Formation. Diagnostic detrital zircon age peaks that occur at 516–529 Ma, 1440–1448 Ma, and 1690–1708 Ma correspond to established ages of the Precambrian basement rocks and suites of granitic plutons associated with the southern Front Range and Wet Mountains Complex in central Colorado. The Wet Mountains Complex is an unusual and major contribution to the typical Mesozoic sediment sources on the Colorado Plateau. The unusually high fractional intensity of sediments derived from these Cambrian and Proterozoic sources suggests a drainage basin reorganization occurred in the local highlands that essentially flooded the Central Colorado Trough with sediments and caused a shift from eolian to lacustrine environment, as Laurentia moved northward.