HR: 09:45h
AN: T51D-08    [Abstracts]
TI: Uplift of the Colorado Plateau and Rocky Mountains during the Laramide Orogeny: a Finite Element Study
AU: * Luo, G
EM: glk82@mizzou.edu
AF: University of Missouri-Columbia, 101 Geology, Columbia, MO 65211 United States
AU: Liu, M
EM: lium@missouri.edu
AF: University of Missouri-Columbia, 101 Geology, Columbia, MO 65211 United States
AB: The Laramide deformation, characterized by basement-cored compression and uplifts in the central and southern Rocky Mountains, has been related to flat subduction of the Farallon plate. Previous modeling has shown that the flat subduction may have peeled away the mantle lithosphere (delamination) under western US, and the associated basal shear could have driven an eastward crustal flow that thickened the crust in the Rocky Mountain region. An alternative hypothesis has emerged in recent years from paleoelevation studies that suggest the existence of an elevated Sevier Plateau in much of the western Cordillera since Late Cretaceous. It has been argued that gravitational potential energy from this plateau could have driven crustal flow to lead to uplift of the Colorado Plateau and the Rocky mountains. We have constructed a 2-D finite element method to test this hypothesis. A series of numerical experiments has been conducted to assess the relative roles of gravitational spreading, plate boundary forces, and basal shear in the Laramide orogeny. Our results indicate that tectonic compression from the plate boundary has little effects on the Laramide deformation, whereas both gravitational buoyancy force and basal shear could have played a major role in the uplift of the Colorado Plateau and the Rocky Mountains. Gravitational spreading of an elevated Sevier Plateau would have caused an eastward propagation of uplifts, whereas basal shear under much of the western Cordillera would have caused faster and earlier uplift in the Rocky Mountains than in the Colorado Plateau. These results provide a framework for further testing of the driving mechanisms of the Laramide orogeny by refined constraints on the deformation history of these regions.
DE: 9350 North America
DE: 9604 Cenozoic
DE: 8102 Continental contractional orogenic belts
DE: 8110 Continental tectonics--general (0905)
DE: 3210 Modeling
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting