River geomorphology reveals distinct patterns and causes of elevation change between the northern and southern Sierra Nevada, California, USA.
Abstract
The timing, rates, and spatial patterns of elevation change in the Sierra Nevada, California, USA, have been the subject of long, vigorous debate due to their importance in providing constraints to contrasting geodynamic models. Here we combine topographic analysis with landscape evolution modeling to explore the degree to which rivers networks dissecting the range record tectonic forcing. Specifically, we quantify along strike trends in basin shape, stability of drainage divides, and fluvial channel steepness. Despite the presence of deeply incised valleys along the length of the range our analysis reveals striking differences north and south of approximately 37° N. In the north, there are large cross-divide gradients in steady state elevation predicted by the stream power equation, large topographic asymmetry of drainage divides, numerous stream captures, large variability of channel steepness between adjoining basins, and little commonality of knick zones in neighboring basins. In contrast, in the south, drainage divides appear more stable and knick zones are in similar positions in neighboring basins, once scaled by drainage area. River steepness and relief in fluvial valleys generally increases from north to south, but abruptly reaches a peak around 37° N. We suggest that the rivers in the northern Sierras are in a transient state of network incision and reorganization not due to a recent change in tectonic forcing, but rather due to reestablishment of a fluvial network after Tertiary volcanism filled and smoothed preexisting topography. In contrast, it appears that the rivers of the southern Sierras are responding to localized rapid uplift rates.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.T24A..04M
- Keywords:
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- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSESDE: 1815 Erosion;
- HYDROLOGYDE: 8175 Tectonics and landscape evolution;
- TECTONOPHYSICSDE: 8177 Tectonics and climatic interactions;
- TECTONOPHYSICS