HR: 17:00h
AN: T14C-05    [Abstracts]
TI: Links between erosion and tectonics in basement-cored uplift provinces: Theory and applications to the central Andes
AU: * Hilley, G E
EM: hilley@stanford.edu
AF: Department of Geological and Environmental Sciences, Department of Geological and Environmental Sciences Stanford University 450 Serra Mall, Stanford, CA 94305, United States
AU: Strecker, M R
EM: strecker@rz.uni-potsdam.de
AF: Institut für Geowissenschaften, Institut für Geowissenschaften Universität Potsdam, Potsdam, 14415, Germany
AB: Recently, modeling and field studies have explored the potential interactions between erosion and tectonics of simple, mechanically homogeneous orogens. In this contribution, we explore the potential influence of pre- existing geologic structures on the development of ranges in basement-cored uplift provinces. These provinces are often characterized by high-angle reverse faulting along preexisting crustal heterogeneities, which may greatly affect the mechanics of deformation and the coupling between erosion and orogenic structure. To understand how deformation and erosion may be coupled in such situations, we model the mechanics and erosion of mountain belts in which the spatial distribution of deformation is largely influenced by the presence of preexisting high-angle faults. In this case, deformation is accommodated along, and topography is built above the weakest of these structures. However, topographic loading increases lithostatic stresses beneath these regions, and as a result, our models indicate that active deformation may migrate to frictionally stronger structures in adjacent regions where lithostatic loading is lower. In cases where erosional processes are more vigorous and may subdue surface slopes, the lower lithostatic loads inhibit the migration of deformation to frictionally stronger structures in adjacent regions. We apply this theory to the development of two basement-cored uplifts in the central Andes where tectonic circumstances are similar, but climate (and presumably erosion rates) are different. In the wetter and more erosive mountain range, deformation appears localized on specific structures over Myr time-scales, but in the dryer, less erosive range, deformation is broadly distributed across several high-angle reverse faults as our model predicts. Our model results and field observations suggest that while pre-existing geologic structures may largely determine the potential loci of deformation in such situations, erosional processes may play a role in determining the longevity and sequence of uplift within such ranges. Thus, in these types of tectonic environments, it is possible that both the long-term geologic history and current erosional processes may play important roles in moderating deformation.
DE: 1824 Geomorphology: general (1625)
DE: 8107 Continental neotectonics (8002)
DE: 8108 Continental tectonics: compressional
DE: 8175 Tectonics and landscape evolution
DE: 8177 Tectonics and climatic interactions
SC: Tectonophysics [T]
MN: 2007 Fall Meeting