Model for tectonically driven incision of the younger than 6 Ma Grand Canyon

Accurate models for the incision of the Grand Canyon must include characterization of tectonic influences on incision dynamics such as active faulting and mantle to surface fluid interconnections. These young tectonic features support other geologic data that indicate that the Grand Canyon has been...

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Bibliographic Details
Published in:Geology (Boulder) 2008-11, Vol.36 (11), p.835-838
Main Authors: Karlstrom, Karl E, Crow, Ryan, Crossey, L. J, Coblentz, D, van Wijk, J. W
Format: Article
Language:English
Subjects:
active faults
age
aquifers
Arizona
Basin and Range Province
canyons
carbonate rocks
Cenozoic
Coconino County Arizona
Colorado Plateau
erosion features
erosion rates
faults
geodynamics
Geomorphology
Grand Canyon
Hurricane Fault
incised valleys
karst
Neogene
neotectonics
North America
Plate tectonics
sedimentary rocks
speleothems
Structural geology
tectonics
Tertiary
Tomography
travertine
U/Pb
United States
uplifts
water table
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Summary:Accurate models for the incision of the Grand Canyon must include characterization of tectonic influences on incision dynamics such as active faulting and mantle to surface fluid interconnections. These young tectonic features support other geologic data that indicate that the Grand Canyon has been carved in the past 6 Ma. New U-Pb dates on speleothems are reinterpreted here in terms of improved geologic constraints and understanding of the modern aquifer. The combined data suggest that Grand Canyon incision rates have been relatively steady since 3-4 Ma. Differences in rates in the eastern (175-250 m/Ma) and western (50-80 m/Ma) Grand Canyon are explained by Neogene fault block uplift across the Toroweap-Hurricane system. Mantle tomography shows an abrupt step in mantle velocities near the Colorado Plateau edge, and geodynamic modeling suggests that upwelling asthenosphere is driving uplift of the Colorado Plateau margin relative to the Basin and Range. Our model for dynamic surface uplift in the past 6 Ma contrasts with the notion of passive incision of the Grand Canyon due solely to river integration and geomorphic response to base-level fall.
ISSN:0091-7613
1943-2682
DOI:10.1130/G25032A.1