Does decreasing paraglacial sediment supply slow knickpoint retreat?

Jansen, J.D., Fabel, D. , Bishop, P., Xu, S., Schnabel, C. and Codilean, A.T. (2011) Does decreasing paraglacial sediment supply slow knickpoint retreat? Geology, 39(6), pp. 543-546. (doi:10.1130/G32018.1)

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Abstract

In four rivers in western Scotland for which there is a well constrained record of relative base-level fall, the rate of postglacial bedrock erosion is quantifi ed by measuring the concentration of in situ cosmogenic 10Be on strath terraces downstream of headward retreating knickpoints. Along-channel gradients in 10Be exposure age show two distinct trends: upstream younging and constant age, which we interpret as diagnostic of knickpoint retreat and diffusive transport-limited incision, respectively. We show that bedrock channel incision and regional formation of strath terraces began shortly after deglaciation (ca. 11.5 ka), and that knickpoint retreat rates peaked in the early to mid-Holocene. Erosion rates have since decreased by two orders of magnitude, converging in the late Holocene to low rates independent of stream power per unit channel area. We infer this regional slowing in postglacial knickpoint retreat to be the result of the depletion of paraglacial sediment supply over the Holocene, leading to a defi ciency in “tools” for bedrock erosion. Our results imply that episodes of major fl uvial erosion may be in tune with glacial cycles, and that sediment depletion following glacial-interglacial transitions may be an important cause of bedrock erosion rate variations in rivers draining glaciated landscapes.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Fabel, Dr Derek and Schnabel, Dr Christoph and Xu, Dr Sheng and Jansen, Dr John and Bishop, Professor Paul
Authors: Jansen, J.D., Fabel, D., Bishop, P., Xu, S., Schnabel, C., and Codilean, A.T.
Subjects:Q Science > QE Geology
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Geology
ISSN:0091-7613
ISSN (Online):1943-2682
Published Online:04 May 2011

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
390921Using the glacioisostatic uplift of N Britain to assess the controls on knickpoint recession in bedrock river channelsPaul BishopNatural Environment Research Council (NERC)NE/C510416/1School of Geographical and Earth Sciences