TY - JOUR
T1 - Transient fluvial incision in the headwaters of the Yellow River, northeastern Tibet, China
AU - Harkins, Nathan
AU - Kirby, Eric
AU - Heimsath, Arjun
AU - Robinson, Ruth
AU - Reiser, Uwe
PY - 2007/9/24
Y1 - 2007/9/24
N2 - We utilize topographic analysis of channel profiles combined with field measurements of erosion rates to explore the distribution of channel incision in the Anyemaqen Shan, a broad mountainous region in the northeastern Tibetan plateau. Tributary channels to the Yellow River display systematic downstream increases in channel gradient associated with convex upward longitudinal profiles. Steep lower reaches of channels are associated with rapid (>1 m/ka) incision rates along the Yellow River, while upstream reaches are associated with relatively slow (0.05-0.1 m/ka) erosion of soil-mantled uplands. Covariance between erosion rates and channel steepness indices suggest that channels are adjusted to match long-wavelength differential rock uplift across the range. Geologic constraints indicate that rapid incision downstream of the range is associated with excavation of basin fill driven by changes in relative base level farther downstream. The upstream limit of this wave of transient incision is marked by a series of knickpoints that are found at nearly the same elevation throughout the watershed, consistent with knickpoint migration as a kinematic, rather than diffusional, wave. Tributary channel gradients downstream of knickpoints, however, display a progressive adjustment to increased incision rates that may reflect the influence of increased sediment flux. Comparison of observed channel profiles to a stream power model of fluvial behavior reveals that the rate of knickpoint propagation can only be explained if the erosional efficiency coefficient (K) increases during incision. Our results thus highlight the utility of channel profile analysis to reconstruct the fluvial response to both active tectonism and external changes in base level.
AB - We utilize topographic analysis of channel profiles combined with field measurements of erosion rates to explore the distribution of channel incision in the Anyemaqen Shan, a broad mountainous region in the northeastern Tibetan plateau. Tributary channels to the Yellow River display systematic downstream increases in channel gradient associated with convex upward longitudinal profiles. Steep lower reaches of channels are associated with rapid (>1 m/ka) incision rates along the Yellow River, while upstream reaches are associated with relatively slow (0.05-0.1 m/ka) erosion of soil-mantled uplands. Covariance between erosion rates and channel steepness indices suggest that channels are adjusted to match long-wavelength differential rock uplift across the range. Geologic constraints indicate that rapid incision downstream of the range is associated with excavation of basin fill driven by changes in relative base level farther downstream. The upstream limit of this wave of transient incision is marked by a series of knickpoints that are found at nearly the same elevation throughout the watershed, consistent with knickpoint migration as a kinematic, rather than diffusional, wave. Tributary channel gradients downstream of knickpoints, however, display a progressive adjustment to increased incision rates that may reflect the influence of increased sediment flux. Comparison of observed channel profiles to a stream power model of fluvial behavior reveals that the rate of knickpoint propagation can only be explained if the erosional efficiency coefficient (K) increases during incision. Our results thus highlight the utility of channel profile analysis to reconstruct the fluvial response to both active tectonism and external changes in base level.
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U2 - 10.1029/2006JF000570
DO - 10.1029/2006JF000570
M3 - Article
AN - SCOPUS:36248937667
SN - 2169-9003
VL - 112
JO - Journal of Geophysical Research: Earth Surface
JF - Journal of Geophysical Research: Earth Surface
IS - 3
M1 - F03S04
ER -