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Project Summary
Personnel:
Will Ouimet (Ph.D.) Leigh Royden (Ph.D.) Kip Hodges (Ph.D.)
Using low-temperature thermochronology we
have focused on trying to better constrain the initiation of major
river incision along the eastern margin by analyzing three
age-elevation transects, one collected in the Dadu river gorge, one in
the Yalong, and the final one in the Yangtze. Previous interpretations
published in Geology (Clark et al., 2005, “Late Cenozoic uplift of
southeastern Tibet”) identified a two-step erosion history of
accelerated incision into slowly eroding, relict landscape. However,
none of Clark et al.'s transects captured the onset of accelerated
incision. New data confirms the acceleration of erosion at ~10 Ma in a
single transect within the Dadu River gorge. Data from the Yalong and
Yangtze River gorges indicate the same long-term exhumation rates
(0.3-0.4 mm/yr) as the Dadu, but slightly different timing for the
onset of major river incision.
Our landscape evolution studies have focused
on the processes, rates and forms of erosion and river incision in
Eastern Tibet. We use an integration of remote sensing and digital
analysis of topographic data and satellite imagery along with
geomorphic observations and measurements from field work, together with
cosmogenic and luminescence dating techniques. We recently completed
the systematic measurement of short-term (102-105 yr) erosion rates at
the basin scale throughout the eastern margin of the Tibetan Plateau.
We use these data to: (1) complement long-term rates (i.e., from
low-temperature thermochronology); (2) characterize the transient
morphology of the eastern Tibet landscape; and (3) address fundamental
relationships between erosion and topography.
We have also studied how landslides exert
control on river profile form in eastern Tibet. Large landslides are a
prominent feature of hillslope erosion in steep, actively incising
landscapes, yet few models of bedrock river incision and landscape
evolution allow for dynamic feedbacks between river incision and the
influence of large landslides. Examples from the eastern margin of the
Tibetan plateau highlight the interaction between landslide dams,
channel morphology, longitudinal river profiles, and river incision. We
use these examples to motivate and formulate a simple, probabilistic,
numerical model which provides a quantitative framework for evaluating
how landslides influence long-term river incision and landscapes in
general.
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