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Does decreasing paraglacial sediment supply slow knickpoint retreat?

Journal Article


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 quantified 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 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.

Authors


  •   Jansen, John D. (external author)
  •   Fabel, Derek (external author)
  •   Bishop, Paul (external author)
  •   Xu, Sheng (external author)
  •   Schnabel, Christoph (external author)
  •   Codilean, Alexandru Tiberiu.

Publication Date


  • 2011

Citation


  • Jansen, J. D., Fabel, D., Bishop, P., Xu, S., Schnabel, C. & Codilean, A. T. (2011). Does decreasing paraglacial sediment supply slow knickpoint retreat?. Geology (Boulder), 39 (6), 543-546.

Scopus Eid


  • 2-s2.0-79959315785

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/352

Number Of Pages


  • 3

Start Page


  • 543

End Page


  • 546

Volume


  • 39

Issue


  • 6

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 quantified 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 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.

Authors


  •   Jansen, John D. (external author)
  •   Fabel, Derek (external author)
  •   Bishop, Paul (external author)
  •   Xu, Sheng (external author)
  •   Schnabel, Christoph (external author)
  •   Codilean, Alexandru Tiberiu.

Publication Date


  • 2011

Citation


  • Jansen, J. D., Fabel, D., Bishop, P., Xu, S., Schnabel, C. & Codilean, A. T. (2011). Does decreasing paraglacial sediment supply slow knickpoint retreat?. Geology (Boulder), 39 (6), 543-546.

Scopus Eid


  • 2-s2.0-79959315785

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/352

Number Of Pages


  • 3

Start Page


  • 543

End Page


  • 546

Volume


  • 39

Issue


  • 6