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Abrasion regimes in fluvial bedrock incision

Beer, Alexander R. and Lamb, Michael P. (2021) Abrasion regimes in fluvial bedrock incision. Geology, 49 (6). pp. 682-686. ISSN 0091-7613. doi:10.1130/g48466.1.

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River incision into bedrock drives landscape evolution and couples surface changes to climate and tectonics in uplands. Mechanistic bedrock erosion modeling has focused on plucking—the hydraulic removal of large loosened rock fragments—and on abrasion—the slower fracturing-driven removal of rock due to impacts of transported sediment—which produces sand- or silt-sized fragments at the mineral grain scale (i.e., wear). An abrasion subregime (macro-abrasion) has been hypothesized to exist under high impact energies typical of cobble or boulder transport in mountain rivers, in which larger bedrock fragments can be generated. We conducted dry impact abrasion experiments across a wide range of impact energies and found that gravel-sized fragments were generated when the impact energy divided by squared impactor diameter exceeded 1 kJ/m². However, the total abraded volume followed the same kinetic-energy scaling regardless of fragment size, holding over 13 orders of magnitude in impact energy and supporting a general abrasion law. Application to natural bedrock rivers shows that many of them likely can generate large fragments, especially in steep mountain streams and during large floods, transporting boulders in excess of 0.6 m diameter. In this regime, even single impacts can cause changes in riverbed topography that may drive morphodynamic feedbacks.

Item Type:Article
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URLURL TypeDescription
Beer, Alexander R.0000-0001-7538-6727
Lamb, Michael P.0000-0002-5701-0504
Additional Information:© 2021 Geological Society of America. Manuscript received 3 March 2020; Revised manuscript received 1 October 2020; Manuscript accepted 16 December 2020. We thank Tom Ulizio and Brian Fuller for help with the experimental setup; Owen Kingstedt for tensile strength measurements; and Joel Scheingross for assistance with coding. Leonard Sklar, Norihiro Izumi, and an anonymous reviewer greatly helped improve a former version of the manuscript. This study was supported by Swiss National Science Foundation (SNSF) grants IZK0Z2_168552/1 and P2EZP2_172109 to Beer, and by NASA grant 80NSSC19K1269 to Lamb.
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)IZK0Z2_168552/1
Swiss National Science Foundation (SNSF)P2EZP2_172109
Issue or Number:6
Record Number:CaltechAUTHORS:20210225-153527227
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Official Citation:Beer, A.R., and Lamb, M.P., 2021, Abrasion regimes in fluvial bedrock incision: Geology, v. 49, p. 682–686,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108224
Deposited By: Tony Diaz
Deposited On:25 Feb 2021 23:58
Last Modified:03 Jun 2021 18:59

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