Journal of Geophysical Research: Earth Surface
© 2014 American Geophysical Union
Impact Factor: 3.44
ISI Journal Citation Reports © Ranking: 2013: 24/173 (Geosciences Multidisciplinary)
Online ISSN: 2169-9011
Associated Title(s): Journal of Geophysical Research
Using cosmogenic nuclides to quantify pebble abrasion in rivers
Sediment transport drives channel erosion and shaping of rivers, so understanding sediment dynamics is a key factor in understanding landscape evolution. Rates of river bedrock erosion depend on the properties of sediment transport, including the grain size distribution of transported sediment and the speed at which sediment moves. However, scientists' knowledge of sediment transport in rivers over long time periods or long distances is limited because there are few methods of observing grain transport over long distances or timescales. Carretier and Regard (2011) show that the concentrations of cosmogenic radionuclides in pebbles vary during river transport. Higher levels of these nuclides can accumulate if the rock is exposed, but concentrations decline as clasts (rock fragments) break and wear down. The authors proposed a model for the downstream evolution of cosmogenic radionuclide concentrations in clasts. They show that in some cases concentrations of these nuclides can be used to determine bounds on clast velocity and abrasion. The model predicts that when clast breakdown (attrition) is high, cosmogenic nuclide concentrations decrease downstream. On the other hand, if attrition is small and river transport slow, cosmogenic nuclide concentrations increase downstream. Therefore, measuring cosmogenic radionuclide concentrations in clasts could help researchers determine the rate of sediment transport or clast attrition in rivers.