Reconstruction of Topography and Lithosphere Dynamics Within the Basin and Range of Western North America Since 36 Ma
Abstract
The complex deformation history of the western U.S. since 36 Ma involved a dramatic transition from a subduction-dominated to a transform-dominated margin, with widespread extension within the interior Basin and Range region. This deformation history altered the topography and drainage patterns and basins throughout the southwest. We perform a comprehensive analysis of the dynamics of the plate boundary zone in the western U.S. since 36 Ma, focusing on the U.S. Basin and Range region, with the goal of understanding the link between mantle dynamics, crustal deformation history, and topography evolution. Using position estimates from McQuarrie and Wernicke [2005], we determine lithospheric strain rates through time and integrate these to determine estimates of crustal thickness evolution. We generate dynamic models to test a number of paleotopographic models (which produce effective body forces) that, together with the mantle contribution, produce compatible directions and magnitudes of extension and shear strain rate through time in the lithosphere. The mantle coupling input is determined using adjoint solutions to move tomography-constrained convection simulations backward. We simultaneously calculate the dynamics of subducting oceanic lithosphere and tomography-driven mantle buoyancy anomalies. These convection simulations provide the lower boundary conditions in the dynamic models. Topography estimates not only incorporate crustal thickness estimates over time, they also include time-dependent dynamic topography estimates from the convection simulations. Our effort on the dynamics will be combined with other independent geochemical constraints provided by the dating of fluorite deposits within fault-associated veins. These fluorite deposits are proposed to be used as a timing constraint for mantle fluid input. Furthermore, our topography, stress, and strain rate models are being used to test the hypothesis that topographic roughness has provided a major control on mammal diversity evolution within the U.S. Basin and Range region since 36 Ma.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.T52C..03H
- Keywords:
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- 3909 Elasticity and anelasticity;
- MINERAL PHYSICSDE: 8164 Stresses: crust and lithosphere;
- TECTONOPHYSICSDE: 8168 Stresses: general;
- TECTONOPHYSICS