HR: 1340h
AN: T23C-0577    [Abstracts]
TI: Reconstructing Paleoelevation of the Cenozoic North American Cordillera- The Stable Isotope Record of Coupled Basin-Detachment Systems
AU: * Teyssier, C
EM: teyssier@umn.edu
AF: University of Minnesota, Geology and Geophysics 310 Pillsbury Drive SE, Minneapolis, MN 55455 United States
AU: Mulch, A
EM: mulch@pangea.stanford.edu
AF: Stanford University, Earth And Environmental Sciences 450 Serra Mall, Bldg. 320 (GeoCorner), Stanford, CA 94305 United States
AU: Chamberlain, C P
EM: chamb@pangea.stanford.edu
AF: Stanford University, Earth And Environmental Sciences 450 Serra Mall, Bldg. 320 (GeoCorner), Stanford, CA 94305 United States
AB: Commonly, stable isotope-based paleoelevation studies exploit changes in meteoric water composition in the near-surface record. We extend this approach by combining multi-proxy, multi-isotope data from extensional mylonite zones and kinematically linked syntectonic basins that record paleotopographic and climatic changes during Cenozoic extension of the North American Cordillera. Combined stable isotope and geochronological data from Eocene and Oligocene/Miocene extensional detachments of the Shuswap/Kettle/Pioneer (British Columbia/Washington/Idaho) and Raft River/Ruby Mountains core complexes (Utah/Nevada) indicate temporal and spatial variations in Cordilleran topography. Hydrogen, oxygen isotope data from Eocene detachments of the Shuswap/Kettle core complexes suggest mean elevations of ca. 4000 m immediately preceding extensional deformation at 49.0 - 47.0 Ma and indicate that crustal thickening prior to detachment faulting resulted in high mean elevations for the Cordillera north of the Snake River. In contrast, stable isotope data from detachment mylonites of the Raft River and Ruby Mountains core complexes indicate high elevations still present in the Miocene (18-16 Ma). Very similar topographic patterns arise from the stable isotope analysis of the freshwater record in Cenozoic intermontane basins. Our comprehensive dataset traces prominent isotopic shifts in space and time and we interpret these shifts to be the result of spatially varying topographic development of Western North America. Determining the isotopic composition of meteoric water in both low- and high-temperature environments over a wide range of time scales and with variable temporal resolution eliminates some of the problems (e.g. climate vs. topographic forcing) associated with paleoelevation reconstructions based on a single proxy.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 8109 Continental tectonics: extensional (0905)
DE: 8175 Tectonics and landscape evolution
SC: Tectonophysics [T]
MN: Fall Meeting 2005