scholarly journals Detrital-zircon U-Pb evidence precludes paleo–Colorado River sediment in the exposed Muddy Creek Formation of the Virgin River depression

Geosphere ◽  
2014 ◽  
Vol 10 (6) ◽  
pp. 1123-1138 ◽  
Author(s):  
William R. Dickinson ◽  
Karl E. Karlstrom ◽  
Andrew D. Hanson ◽  
George E. Gehrels ◽  
Mark Pecha ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
River Sediment ◽  
Colorado River ◽  
Virgin River ◽  
Muddy Creek Formation ◽  
Muddy Creek

scholarly journals Detrital zircon U-Pb provenance of the Colorado River: A 5 m.y. record of incision into cover strata overlying the Colorado Plateau and adjacent regions

Geosphere ◽  
2015 ◽  
Vol 11 (6) ◽  
pp. 1719-1748 ◽  
Author(s):  
David L. Kimbrough ◽  
Marty Grove ◽  
George E. Gehrels ◽  
Rebecca J. Dorsey ◽  
Keith A. Howard ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
Colorado River ◽  
Colorado Plateau

scholarly journals A constraint on post–6 Ma timing of western Grand Canyon (Arizona, USA) incision removed: Local derivation indicated by ca. 5.4 Ma fluvial deposits below Shivwits Plateau basalts north of Grand Canyon

Geosphere ◽  
2021 ◽  
Author(s):  
A.T. Steelquist ◽  
G.E. Hilley ◽  
I. Lucchitta ◽  
R.A. Young
Keyword(s):  
United States ◽  
Detrital Zircon ◽  
Colorado River ◽  
Landscape Evolution ◽  
Colorado Plateau ◽  
Grand Canyon ◽  
River System ◽  
Fluvial Deposits ◽  
Western Colorado ◽  
Rule Out

The timing of integration of the Colorado River system is central to understanding the landscape evolution of much of the southwestern United States. However, the time at which the Colorado River started incising the westernmost Grand Canyon (Arizona) is still an unsettled question, with conflicting interpretations of both geologic and thermochronologic data from western Grand Canyon. Fluvial gravels on the Shivwits Plateau, north of the canyon, have been reported to contain clasts derived from south of the modern canyon, suggesting the absence of western Grand Canyon at the time of their deposition. In this study, we reassess these deposits using modern geochronologic measurements to determine the age of the deposits and the presence or absence of clasts from south of the Grand Canyon. We could not identify southerly derived clasts, so cannot rule out the existence of a major topographic barrier such as Grand Canyon prior to the age of deposition of the gravels. 40Ar/39Ar analysis of a basalt clast entrained in the upper deposit (in combination with prior data) supports a maximum age of deposition of ca. 5.4 Ma, limiting deposition to post-Miocene, a period from which very few diagnostic and dated fluvial deposits remain in the western Colorado Plateau. Analysis of detrital zircon composition of the sand matrix supports interpretation of the deposit as being locally derived and not part of a major throughgoing river. We suggest that the published constraint of <6 Ma timing of Grand Canyon incision may be removed, given that no clasts that must be sourced from south of Grand Canyon were found in the only known outcrop of gravels under the Shivwits Plateau basalts at Grassy Mountain north of Grand Canyon.

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