HR: 0800h
AN: T51D-1364    [Abstracts]
TI: Computational Modeling of Ductile Folding in Sedimentary Rocks of the Sheep Mountain Anticline, Wyoming
AU: * Borja, R I
EM: borja@stanford.edu
AF: Stanford University, Department of Civil and Environmental Engineering, Stanford, CA 94305 United States
AU: Sanz, P F
EM: pfsanz@stanford.edu
AF: Stanford University, Department of Civil and Environmental Engineering, Stanford, CA 94305 United States
AU: Fiore, P E
EM: pfiore@pangea.stanford.edu
AF: Stanford Univeristy, Department of Geological and Environmental Sciences, Stanford, CA 94305 United States
AU: Pollard, D D
EM: dpollard@pangea.stanford.edu
AF: Stanford Univeristy, Department of Geological and Environmental Sciences, Stanford, CA 94305 United States
AB: Folding of sedimentary rocks occurs at depths in Earth's crust where some layers respond by brittle deformation while others respond by ductile deformation. Folding results from a number of mechanisms including buckling due to lateral tectonic compression and/or slip on thrust faults in the underlying strata. Movements experienced by folded strata are typically very large (tens to hundreds of meters or more) and may include significant rigid body translation and rotation, in addition to the straining of the folded layers. More specific types of straining could include any one or a combination of the following: plate-like bending, in-plane extension, in-plane contraction, and either in-plane or out-of-plane shearing. The stress state resulting from the overburden load, slip on underlying faults, and the associated folding could induce strain localization even as the layer continues to deform plastically. In this paper we present a mathematical model for capturing isothermal ductile folding processes and the accompanying strain localization in sedimentary rocks using nonlinear continuum mechanics and finite element modeling. We use a fully Lagrangian approach along with multiplicative plasticity theory for finite deformations, considering the effects of all three invariants of the stress tensor in the constitutive description. We also simulate the rigid body translation, finite rotation, and subsequent rupturing of preexisting faults using finite deformation kinematics and stick-slip contact mechanics. We apply the technique to simulate the three-dimensional folding of selected Paleozoic and Mesozoic formations located above the Madison limestone in the Sheep Mountain anticline, formed during the Laramide orogeny in the Bighorn Basin, Wyoming. Supported by U.S. Department of Energy, Grant No. DE-FG02-03ER15454, and U.S. National Science Foundation, Grant No. CMG-0417521.
DE: 8000 STRUCTURAL GEOLOGY
DE: 8005 Folds and folding
DE: 8012 High strain deformation zones
DE: 8020 Mechanics, theory, and modeling
SC: Tectonophysics [T]
MN: Fall Meeting 2005