Local topography and erosion rate control regolith thickness along a ridgeline in the Sierra Nevada, California

Gabet, E. J., Mudd, S. M., Milodowski, D. T., Yoo, K., Hurst, M. D. and Dosseto, A. (2015) Local topography and erosion rate control regolith thickness along a ridgeline in the Sierra Nevada, California. Earth Surface Processes and Landforms, 40(13), pp. 1779-1790. (doi: 10.1002/esp.3754)

Abstract

The ridgelines of mountain ranges are a source of geomorphic information unadulterated by the arrival of sedimentfrom upslope. Studies along ridgecrests, therefore, can help identify and isolate the controls on important regolith properties suchas thickness and texture. A 1.5 km section of ridgeline in the Sierra Nevada (CA) with a tenfold decrease in erosion rate (inferred fromridgetop convexity) provided an opportunity to conduct a high-resolution survey of regolith properties and investigate their controls.We found that regolith along the most quickly eroding section of the ridge was the rockiest and had the lowest clay concentrations.Furthermore, a general increase in regolith thickness with a slowing of erosion rate was accompanied by an increase in biomass,changes in vegetation community, broader ridgeline profiles, and an apparent increase in total available moisture. The greatest sourceof variation in regolith thickness at the 10–100 m scale, however, was the local topography along the ridgeline, with the deepest reg-olith in the saddles and the thinnest on the knobs. Because regolith in the saddles had higher surface soil moisture than the knobs, weconclude that the hydrological conditions primarily driven by local topography (i.e. rapid vs. slow drainage and water-storage poten-tial) provide the fundamental controls on regolith thickness through feedbacks incorporating physical weathering by the biota andchemical weathering. Moreover, because the ridgeline saddles are the uppermost extensions of first-order valleys, we propose thatthe fluvial network affects regolith properties in the furthest reaches of the watershed.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Hurst, Dr Martin
• Authors: Gabet, E. J., Mudd, S. M., Milodowski, D. T., Yoo, K., Hurst, M. D., and Dosseto, A.
• Subjects: 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: Earth Surface Processes and Landforms
• Publisher: John Wiley and Sons
• ISSN: 0197-9337
• ISSN (Online): 1096-9837
• Published Online: 28 June 2015