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Episodic bedrock erosion by gully-head migration, Colorado High Plains, USA

June 30, 2016

This study explores the frequency of bedrock exposure in a soil-mantled low-relief (i.e. non-mountainous) landscape. In the High Plains of eastern Colorado, gully headcuts are among the few erosional features that will incise through the soil mantle to expose bedrock. We measured the last time of bedrock exposure using optically stimulated luminescence dating of alluvial sediment overlying bedrock in gully headcuts. Our dating suggests that headcuts in adjacent gullies expose bedrock asynchronously, and therefore, the headcuts are unlikely to have been triggered by a base-level drop in the trunk stream. This finding supports the hypothesis that headcuts can develop locally in gullies as a result of focused scour in locations where hydraulic stress during a flash flood is sufficiently high, and/or ground cover is sufficiently weak, to generate a scour hole that undermines vegetation. Alluvium dating also reveals that gullies have been a persistent part of this landscape since the early Holocene. 

Publication Year 2016
Title Episodic bedrock erosion by gully-head migration, Colorado High Plains, USA
DOI 10.1002/esp.3929
Authors Francis K. Rengers, G.E. Tucker, Shannon Mahan
Publication Type Article
Publication Subtype Journal Article
Series Title Earth Surface Processes and Landforms
Index ID 70160021
Record Source USGS Publications Warehouse
USGS Organization Geologic Hazards Science Center