HR: 15:10h
AN: H43H-07    [Abstracts]
TI: The persistence of plateaus: Sediment-flux driven bedrock incision in the southern Sierra Nevada
AU: * Pelletier, J D
EM: jdpellet@email.arizona.edu
AF: Geosciences Dept., University of Arizona, 1040 E. Fourth St., Tucson, AZ 85749, United States
AB: Hillslope and channel evolution are tightly coupled in sediment-flux-driven models of bedrock channel incision. In this paper I explore the consequences of this coupling for the case of the plateau-dominated landscape of the southern Sierra Nevada, California. I use a sediment-flux-driven incision model to model the fluvial Cenozoic geomorphic evolution and surface uplift history of the range in response to different hypothetical uplift histories. Cosmogenic data for upland erosion and mainstem river incision rates allow the model parameters to be uniquely constrained. Numerical experiments using the sediment-flux-driven model suggest that the modern southern Sierra Nevada was constructed from a ~1.0 km pulse of range-wide surface uplift in the late Cretaceous (~60 Ma) and a ~0.5 km pulse in the late Miocene (~10 Ma). The persistent geomorphic response to late Cretaceous uplift in this model is the result of limited cutting tools supplied from the upland low-relief Boreal Plateau. This uplift history correctly predicts the modern topography of the range, including the approximate elevations and extents of the Chagoopa and Boreal Plateaux and their associated knickpoints. These results indicate that low-relief upland landscapes do not necessarily indicate late Cenozoic surface uplift. Finally, I illustrate some implications of the sediment-flux-driven model for understanding the persistent topography of ancient orogens.
DE: 1824 Geomorphology: general (1625)
DE: 1825 Geomorphology: fluvial (1625)
DE: 1826 Geomorphology: hillslope (1625)
DE: 1849 Numerical approximations and analysis
SC: Hydrology [H]
MN: 2007 Fall Meeting