Influence of lithology on hillslope morphology and response to tectonic forcing in the northern Sierra Nevada of California

Hurst, M. D. , Mudd, S. M., Yoo, K., Attal, M. and Walcott, R. (2013) Influence of lithology on hillslope morphology and response to tectonic forcing in the northern Sierra Nevada of California. Journal of Geophysical Research: Earth Surface, 118(2), pp. 832-851. (doi: 10.1002/jgrf.20049)

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Many geomorphic studies assume that bedrock geology is not a first-order control on landscape form in order to isolate drivers of geomorphic change (e.g., climate or tectonics). Yet underlying geology may influence the efficacy of soil production and sediment transport on hillslopes. We performed quantitative analysis of LiDAR digital terrain models to examine the topographic form of hillslopes in two distinct lithologies in the Feather River catchment in northern California, a granodiorite pluton and metamorphosed volcanics. The two sites, separated by <2 km and spanning similar elevations, were assumed to have similar climatic histories and are experiencing a transience in landscape evolution characterized by a propagating incision wave in response to accelerated surface uplift c. 5 Ma. Responding to increased incision rates, hillslopes in granodiorite tend to have morphology similar to model predictions for steady state hillslopes, suggesting that they adjust rapidly to keep pace with the incision wave. By contrast, hillslopes in metavolcanics exhibit high gradients but lower hilltop curvature indicative of ongoing transient adjustment to incision. We used existing erosion rate data and the curvature of hilltops proximal to the main channels (where hillslopes have most likely adjusted to accelerated erosion rates) to demonstrate that the sediment transport coefficient is higher in granodiorite (8.8 m<sub>2</sub> ka<sub>-1</sub>) than in metavolcanics (4.8 m<sub>2</sub> ka<sub>-1</sub>). Hillslopes in both lithologies get shorter (i.e., drainage density increases) with increasing erosion rates.

Item Type:Articles
Additional Information:This work was supported by a NationalEnvironmental Research Council (NERC) Doctoral Training Grant NE/G524128/1 awarded to M. D. Hurst and NERC NE/H001174/1 to S. M. Mudd.Funding for this work was also provided by the National Science FoundationEAR0819064 (Empirical and Theoretical Integration of Geochemical andMorphologic Evolution of Soil-Covered Hillslopes: Responses to ChannelIncision) to K. Yoo and S. M. Mudd for which LiDAR topographic data wereacquired by the National Center for Airborne Laser Mapping.
Glasgow Author(s) Enlighten ID:Hurst, Dr Martin
Authors: Hurst, M. D., Mudd, S. M., Yoo, K., Attal, M., and Walcott, R.
Subjects:G Geography. Anthropology. Recreation > G Geography (General)
G Geography. Anthropology. Recreation > GA Mathematical geography. Cartography
G Geography. Anthropology. Recreation > GB Physical geography
Q Science > QE Geology
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Journal of Geophysical Research: Earth Surface
Published Online:27 February 2013
Copyright Holders:Copyright © 2015 The Authors3
First Published:First published in Journal of Geophysical Research: Earth Surface 118(2): 832-851
Publisher Policy:Reproduced under a Creative Commons License

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