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Does decreasing paraglacial sediment supply slow knickpoint retreat?
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
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2011 (English)In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 39, no 6, 543-546 p.Article in journal (Refereed) Published
Abstract [en]

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 quantified by measuring the concentration of in situ cosmogenic (10)Be on strath terraces downstream of headward-retreating knickpoints. Along-channel gradients in (10)Be 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 deficiency in tools for bedrock erosion. Our results imply that episodes of major fluvial 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.

Place, publisher, year, edition, pages
2011. Vol. 39, no 6, 543-546 p.
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Earth and Related Environmental Sciences
URN: urn:nbn:se:su:diva-67868DOI: 10.1130/G32018.1ISI: 000291096300008OAI: diva2:471473

authorCount :6

Available from: 2012-01-02 Created: 2012-01-02 Last updated: 2012-09-25Bibliographically approved

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Jansen, John D.
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Department of Physical Geography and Quaternary Geology
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