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Uniform-sense normal simple shear of the continental lithosphere

Wernicke, Brian (1985) Uniform-sense normal simple shear of the continental lithosphere. Canadian Journal of Earth Sciences, 22 (1). pp. 108-125. ISSN 1480-3313. doi:10.1139/e85-009.

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Geophysical studies suggest that the thin crust characteristic of the Basin and Range Province extends eastward beneath the west margin of the Colorado Plateau and Rocky Mountain regions. In Arizona and Utah, zones perhaps over 100 km wide may be defined, bounded on the west by the east limit of upper crustal normal faults that account for more that 10% extension and on the east by the east limit of thinning beneath the Colorado Plateau. A discrepancy exists within these zones between the negligible extension measurable in the upper crust and the substantial extension apparent from crustal thinning, assuming the "discrepant zone" crust was as thick as or thicker than the Colorado Plateau – Rocky Mountain crust prior to extensional tectonism.If various theories appealing to crustal erosion are dismissed, mass balance problems evident in the discrepant zones are most easily resolved by down-to-the-east normal simple shear of the crust, moving lower and middle crustal rocks that initially were within the zones up-and-to-the-west to where they now are locally exposed in the Basin and Range Province. West of the discrepant zones in both Arizona and Utah, east-directed extensional allochthons with large displacement are exposed. These geophysical and geological observations complement one another if it is accepted that the entire crust in both Arizona and Utah failed during extension on gently east-dipping, east-directed, low-angle normal faults and shear zones over a region several hundred kilometres wide.Large-scale, uniform-sense normal simple shear of the crust suggests the entire lithosphere may do the same. Such a hypothesis predicts major lithospheric thinning without crustal thinning will occur in plateau areas in the direction of crustal shear. In the case of the Arizona, Utah, and Red Sea extensional systems, and possibly the Death Valley extensional terrain, a broad topographic arch, typically 1500–2000 m higher than the extended terrain, is present, suggesting lithospheric thinning in areas predicted by the hypothesis.

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Wernicke, Brian0000-0002-7659-8358
Additional Information:© 1985 NRC Research Press. Received February 7, 1984; Revision accepted July 12, 1984. Research leading to this report has been funded by National Science Foundation grants EAR 7713637 to B. C. Burchfiel. EAR 7926346 to B. C. Burchfiel and P. Molnar, and EAR 8219034 to B. P. Wernicke. Discussions with J. M. Bartley and R. J. O'Connell have greatly clarified for me some of the concepts upon which this paper is based. I thank P. C. England and J. M. Bartley for reviewing an early draft of this manuscript and R. A. Price and K. R. McClay for helpful, critical reviews of the penultimate draft.
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Official Citation:Uniform-sense normal simple shear of the continental lithosphere. Brian Wernicke. Canadian Journal of Earth Sciences, 1985, 22:108-125,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98818
Deposited By: Tony Diaz
Deposited On:24 Sep 2019 16:14
Last Modified:16 Nov 2021 17:41

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