HR: 09:00h
AN: T31E-05    [Abstracts]
TI: The Cenozoic Rise and Fall of the Western United States
AU: * Chamberlain, C P
EM: chamb@pangea.stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 United States
AU: Mulch, A
EM: mulch@pangea.Stanford.EDU
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 United States
AU: Horton, T W
EM: thorton@ups.edu
AF: Geology Department, University of Puget Sound, Tacoma, WA 98416 United States
AU: Kent-Corson, M L
EM: malkc@stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 United States
AU: Sherman, L S
EM: sherman3@stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 United States
AU: Davis, S
EM: sjdavis@stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 United States
AU: Hren, M
EM: hren@stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 United States
AU: Teyssier, C
EM: teyssier@tc.umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455 United States
AB: Stable isotopic records collected from intermontane basins throughout Western North United States record regional climate change in response to surface uplift of major mountain ranges, as well as global climate change. We observe an approximately 5 to 10 per mil decrease in d18O of lacustrine, palustrine and paleosol carbonate and chert that occurs at ~47 Ma in southwestern Montana, at ~40 Ma in northeastern Nevada and central Utah, and at ~20 Ma in southern Nevada. These shifts are not observed in the Wind River Basin sections east of the Rocky Mountains, which suggest that the isotopic shifts are the result of regional rather than global climate changes. We interpret these isotopic shifts to be the result of spatially varying topographic development of Western North America with topography migrating southwestward with time. This pattern of surface uplift is roughly consistent with the timing of onset of magmatism in these areas. Moreover, the spatially and temporally varying shift is also observed in neocrystallized white mica found within detachment faults of the core complexes adjacent to these basins. These data, taken together, support tectonic models that link magmatism, crustal extension and topographic development of a large orogenic plateau. From the mid-Miocene to the Pleistocene there is an ~2 per mil increase in d18O values of authigenic minerals in sections throughout the Great Basin, from eastern Oregon and northern Nevada south to Arizona. This increase is not observed east of the Rocky Mountains or in southwestern Montana. We suggest that this decrease is the result of collapse of the uplifted plateau and reorganization of regional climate patterns as southerly-sourced precipitation is drawn into the Great Basin.
DE: 4870 Stable isotopes (0454, 1041)
DE: 4914 Continental climate records
DE: 8177 Tectonics and climatic interactions
DE: 9604 Cenozoic
SC: Tectonophysics [T]
MN: Fall Meeting 2005