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.

scholarly journals Evaluating the Shinumo-Sespe drainage connection: Arguments against the “old” (70–17 Ma) Grand Canyon models for Colorado Plateau drainage evolution

Geosphere ◽  
2020 ◽  
Vol 16 (6) ◽  
pp. 1425-1456
Author(s):  
Karl E. Karlstrom ◽  
Carl E. Jacobson ◽  
Kurt E. Sundell ◽  
Athena Eyster ◽  
Ron Blakey ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
Gulf Of California ◽  
Colorado Plateau ◽  
Grand Canyon ◽  
River System ◽  
Death Valley ◽  
Transverse Ranges ◽  
Drainage Connection ◽  
The Pacific ◽  
History Of

Abstract The provocative hypothesis that the Shinumo Sandstone in the depths of Grand Canyon was the source for clasts of orthoquartzite in conglomerate of the Sespe Formation of coastal California, if verified, would indicate that a major river system flowed southwest from the Colorado Plateau to the Pacific Ocean prior to opening of the Gulf of California, and would imply that Grand Canyon had been carved to within a few hundred meters of its modern depth at the time of this drainage connection. The proposed Eocene Shinumo-Sespe connection, however, is not supported by detrital zircon nor paleomagnetic-inclination data and is refuted by thermochronology that shows that the Shinumo Sandstone of eastern Grand Canyon was >60 °C (∼1.8 km deep) and hence not incised at this time. A proposed 20 Ma (Miocene) Shinumo-Sespe drainage connection based on clasts in the Sespe Formation is also refuted. We point out numerous caveats and non-unique interpretations of paleomagnetic data from clasts. Further, our detrital zircon analysis requires diverse sources for Sespe clasts, with better statistical matches for the four “most-Shinumo-like” Sespe clasts with quartzites of the Big Bear Group and Ontario Ridge metasedimentary succession of the Transverse Ranges, Horse Thief Springs Formation from Death Valley, and Troy Quartzite of central Arizona. Diverse thermochronologic and geologic data also refute a Miocene river pathway through western Grand Canyon and Grand Wash trough. Thus, Sespe clasts do not require a drainage connection from Grand Canyon or the Colorado Plateau and provide no constraints for the history of carving of Grand Canyon. Instead, abundant evidence refutes the “old” (70–17 Ma) Grand Canyon models and supports a <6 Ma Grand Canyon.

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 Supplemental Material: Evaluating the Shinumo-Sespe drainage connection: Arguments against the “old” (70–17 Ma) Grand Canyon models for Colorado Plateau drainage evolution

2020 ◽  
Author(s):  
K.E. Karlstrom ◽  
et al.
Keyword(s):  
Detrital Zircon ◽  
Colorado Plateau ◽  
Grand Canyon ◽  
Quantitative Comparison ◽  
Cross Bedding ◽  
Drainage Connection ◽  
Comparison Results

Table S1: Rotations of measured paleomagnetic paleopoles to test the error introduced by measuring inclinations relative to cross bedding of different orientations instead of horizontal bedding. Table S2: Detrital zircon data used in this study. Table S3: Quantitative comparison results from DZstats.

scholarly journals Supplemental Material: Evaluating the Shinumo-Sespe drainage connection: Arguments against the “old” (70–17 Ma) Grand Canyon models for Colorado Plateau drainage evolution

2020 ◽  
Author(s):  
K.E. Karlstrom ◽  
et al.
Keyword(s):  
Detrital Zircon ◽  
Colorado Plateau ◽  
Grand Canyon ◽  
Quantitative Comparison ◽  
Cross Bedding ◽  
Drainage Connection ◽  
Comparison Results

Table S1: Rotations of measured paleomagnetic paleopoles to test the error introduced by measuring inclinations relative to cross bedding of different orientations instead of horizontal bedding. Table S2: Detrital zircon data used in this study. Table S3: Quantitative comparison results from DZstats.

scholarly journals Cenozoic incision history of the Little Colorado River: Its role in carving Grand Canyon and onset of rapid incision in the past ca. 2 Ma in the Colorado River System

Geosphere ◽  
2016 ◽  
Vol 13 (1) ◽  
pp. 49-81 ◽  
Author(s):  
K.E. Karlstrom ◽  
L.J. Crossey ◽  
E. Embid ◽  
R. Crow ◽  
M. Heizler ◽  
...  
Keyword(s):  
Colorado River ◽  
Grand Canyon ◽  
River System ◽  
The Past ◽  
History Of

Redefining the age of the lower Colorado River, southwestern United States

Geology ◽  
2021 ◽  
Author(s):  
R.S. Crow ◽  
J. Schwing ◽  
K.E. Karlstrom ◽  
M. Heizler ◽  
P.A. Pearthree ◽  
...  
Keyword(s):  
United States ◽  
Gulf Of California ◽  
Colorado River ◽  
Grand Canyon ◽  
Plate Motion ◽  
Southwestern United States ◽  
Northern Mexico ◽  
Base Level ◽  
Salton Trough ◽  
Lower Colorado River

Sanidine dating and magnetostratigraphy constrain the timing of integration of the lower Colorado River (southwestern United States and northern Mexico) with the evolving Gulf of California. The Colorado River arrived at Cottonwood Valley (Nevada and Arizona) after 5.24 Ma (during or after the Thvera subchron). The river reached the proto–Gulf of California once between 4.80 and 4.63 Ma (during the C3n.2r subchron), not at 5.3 Ma and 5.0 Ma as previously proposed. Duplication of section across newly identified strands of the Earthquake Valley fault zone (California) probably explains the discrepancy. The data also imply the start of focused plate motion and basin development in the Salton Trough (California) at 6–6.5 Ma and relative tectonic stability of the southernmost part of the lower Colorado River corridor after its integration. After integration, the Colorado River quickly incised through sediment-filled basins and divides between them as it also likely excavated Grand Canyon (Arizona). The liberated sediment from throughout the system led to deposition of hundreds of meters of Bullhead Alluvium downstream of Grand Canyon after 4.6 Ma as the river adjusted to its lower base level.

Eocene–Recent drainage evolution of the Colorado River and its precursor: an integrated provenance perspective from SW California

2018 ◽  
Vol 488 (1) ◽  
pp. 47-72 ◽  
Author(s):  
Uisdean Nicholson ◽  
Andrew Carter ◽  
Paula Robinson ◽  
David I. M. Macdonald
Keyword(s):  
Colorado River ◽  
Colorado Plateau ◽  
River System ◽  
Large River ◽  
Detrital Zircons ◽  
Heavy Mineral ◽  
Continental Scale ◽  
The North ◽  
Sediment Routing ◽  
The Usa

AbstractThe Colorado River in the SW of the USA is one of Earth's few continental-scale rivers with an active margin delta. Deformation along this transform margin, as well as associated intra-plate strain, has resulted in significant changes in sediment routing from the continental interior and post-depositional translation of older deltaic units. The oldest candidate deposits, fluvial sandstones of the Eocene Sespe Group, are now exposed in the Santa Monica Mountains, 300 km to the north of the Colorado River. Heavy mineral data from this basin indicate that sediment was sourced by a large river system, with some affinity to the early Pliocene Colorado River, but was unlikely to have been integrated across the Colorado Plateau. Sedimentological and mineralogical evidence from the earliest (c. 5.3 Ma) unequivocal Colorado River-derived sediments in the Salton Trough provide evidence for a rapid transition from locally derived sedimentation. Lack of evidence for a precursor phase of suspended-load sediment suggests that drainage capture took place in a proximal position, favouring a ‘top-down’ process of lake spillover. Following drainage integration, significant changes in heavy mineral assemblages of fluvio-deltaic sediments, particularly evident from apatite–tourmaline and garnet–zircon indices, as well as U–Pb ages of detrital zircons, document the integration of the fluvial system to its present form and progressive incision of the Colorado Plateau from the Miocene to the present.

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