Transient fluvial incision in the headwaters of the Yellow River, northeastern Tibet, China

被引:262
作者
Harkins, Nathan [1 ]
Kirby, Eric
Heimsath, Arjun
Robinson, Ruth
Reiser, Uwe
机构
[1] Penn State Univ, Dept Geosci, University Pk, PA 16802 USA
[2] Dartmouth Coll, Dept Earth Sci, Hanover, NH 03755 USA
[3] Univ St Andrews, Sch Geog & Geosci, St Andrews, Fife, Scotland
[4] Victoria Univ Wellington, Sch Earth Sci, Wellington, New Zealand
关键词
D O I
10.1029/2006JF000570
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
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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页数:21
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