New constraints on sediment-flux-dependent river incision: Implications for extracting tectonic signals from river profiles
Abstract
We present new field data from rivers draining across activenormal faults that incise across the same lithology at the fault,have been subjected to similar climatic regimes and tectonicsettings, and were perturbed by a well-documented increase infault slip rate ca. 1 Ma. In spite of these similarities, therivers exhibit markedly different long profiles and patternsof catchment incision. We use channel slope and hydraulic geometrydata for each river to calculate bed shear stresses (<IMG SRC="/math/tau.gif" ALT="{tau}" BORDER="0">b), andshow that there is no simple relationship between peak <IMG SRC="/math/tau.gif" ALT="{tau}" BORDER="0">b andthe relative uplift rates across the faults, U, which differby a factor of four. The long-term average sediment supply toeach channel (Qs), estimated from time-averaged catchment erosionrates, can explain the <IMG SRC="/math/tau.gif" ALT="{tau}" BORDER="0">b versus U data if bedload modulatesbedrock incision rate, E, in a strongly nonlinear way. Togetherthese field data allow us, for the first time, to evaluate theoreticalpredictions of the role of sediment on river profile evolutionand to quantify the magnitude of the effect in natural systems.
- Publication:
-
Geology
- Pub Date:
- July 2008
- DOI:
- 10.1130/G24681A.1
- Bibcode:
- 2008Geo....36..535C