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1282447 
Journal Article 
Does decreasing paraglacial sediment supply slow knickpoint retreat? 
Jansen, JD; Fabel, D; Bishop, P; Xu, S; Schnabel, C; Codilean, AT 
2011 
Yes 
Geology
ISSN: 0091-7613 
Geological Society of America (GSA) 
United States (USA) 
39 
6 (June 2011) 
543-546 
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 (super 10) Be on strath terraces downstream of headward-retreating knickpoints. Along-channel gradients in (super 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. 
Spean River; strath terraces; erosion rates; Scotland; glaciated terrains; metals; rivers; channels; glaciation; Cenozoic; Coe River; incised valleys; Etive River; fjords; knickpoints; sediment supply; shore features; United Kingdom; erosion; beryllium; Europe; isotopes; terraces; exposure age; water erosion; fluvial features; western Scotland; Great Britain; deglaciation; water-rock interaction; alkaline earth metals; geochronology; Be-10; Loch Linnhe; Leven River; Quaternary; postglacial environment; geomorphology; radioactive isotopes; Western Europe; cycles; landscapes; glacial features; Holocene