Lowland river responses to intraplate tectonism and climate forcing quantified with luminescence and cosmogenic 10Be

Jansen, J.D. et al. (2013) Lowland river responses to intraplate tectonism and climate forcing quantified with luminescence and cosmogenic 10Be. Earth and Planetary Science Letters, 366, pp. 49-58. (doi: 10.1016/j.epsl.2013.02.007)

Abstract

Intraplate tectonism has produced large-scale folding that steers regional drainage systems, such as the 1600 km-long Cooper Ck, en route to Australia’s continental depocentre at Lake Eyre. We apply cosmogenic 10Be exposure dating in bedrock, and luminescence dating in sediment, to quantify the erosional and depositional response of Cooper Ck where it incises the rising Innamincka Dome. The detachment of bedrock joint-blocks during extreme floods governs the minimum rate of incision (17.4±6.5 mm/ky) estimated using a numerical model of episodic erosion calibrated with our 10Be measurements. The last big-flood phase occurred no earlier than ~112–121ka. Upstream of the Innamincka Dome long-term rates of alluvial deposition, partly reflecting synclinal-basin subsidence, are estimated from 47 luminescence dates in sediments accumulated since ~270 ka. Sequestration of sediment in subsiding basins such as these may account for the lack of Quaternary accumulation in Lake Eyre, and moreover suggests that notions of a single primary depocentre at base-level may poorly represent lowland, arid-zone rivers. Over the period ~75–55 ka Cooper Ck changed from a bedload- dominant, laterally-active meandering river to a muddy anabranching channel network up to 60 km wide. We propose that this shift in river pattern was a product of base-level rise linked with the slowly deforming syncline–anticline structure, coupled with a climate-forced reduction in discharge. The uniform valley slope along this subsiding alluvial and rising bedrock system represents an adjustment between the relative rates of deformation and the ability of greatly enhanced flows at times during the Quaternary to incise the rising anticline. Hence, tectonic and climate controls are balanced in the long term.

• Item Type: Articles
• Additional Information: NOTICE: this is the author’s version of a work that was accepted for publication in Earth and Planetary Science Letters. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Earth and Planetary Science Letters, 366, 2013. http://dx.doi.org/10.1016/j.epsl.2013.02.007
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Fabel, Dr Derek
• Authors: Jansen, J.D., Nanson, G.C., Cohen, T.J., Fulioka, T., Fabel, D., Larsen, J.R., Codilean, A.T., Price, D.M., Bowman, H.H., May, J.-H., and Gliganic, L.A.
• Subjects: G Geography. Anthropology. Recreation > GB Physical geography; Q Science > QE Geology
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences
• Research Group: Earth Surface Processes
• Journal Name: Earth and Planetary Science Letters
• Journal Abbr.: EPSL
• Publisher: Elsevier
• ISSN: 0012-821X
• ISSN (Online): 1385-013X
• Copyright Holders: Copyright © 2013 Elsevier Ltd.
• First Published: First published in Earth and Planetary Science Letters 366:49-58
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher