Tectonic uplift, threshold hillslopes, and denudation rates in a developing mountain range

Steven A. Binnie*, William M. Phillips, Michael A. Summerfield, L. Keith Fifield

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    174 Citations (Scopus)

    Abstract

    Studies across a broad range of drainage basins have established a positive correlation between mean slope gradient and denudation rates. It has been suggested, however, that this relationship breaks down for catchments where slopes are at their threshold angle of stability because, in such cases, denudation is controlled by the rate of tectonic uplift through the rate of channel incision and frequency of slope failure. This mechanism is evaluated for the San Bernardino Mountains, California, a nascent range that incorporates both threshold hill-slopes and remnants of pre-uplift topography. Concentrations of in situ-produced cosmogenic 10Be in alluvial sediments are used to quantify catchment-wide denudation rates and show a broadly linear relationship with mean slope gradient up to ∼30°: above this value denudation rates vary substantially for similar mean slope gradients. We propose that this decoupling in the slope gradient-denudation rate relationship marks the emergence of threshold topography and coincides with the transition from transport-limited to detachment-limited denudation. The survival in the San Bernardino Mountains of surfaces formed prior to uplift provides information on the topographic evolution of the range, in particular the transition from slope-gradient-dependent rates of denudation to a regime where denudation rates are controlled by rates of tectonic uplift. This type of transition may represent a general model for the denudational response to orogenic uplift and topographic evolution during the early stages of mountain building.

    Original languageEnglish
    Pages (from-to)743-746
    Number of pages4
    JournalGeology
    Volume35
    Issue number8
    DOIs
    Publication statusPublished - Aug 2007

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