Fluvial bedrock incision in the active mountain belt of Taiwan from in situ-produced cosmogenic nuclides.

Schaller, M. and Hovius, N. and Willett, S. D. and Ivy-Ochs, S. and Synal, H. A. and Chen, M. C. (2005) Fluvial bedrock incision in the active mountain belt of Taiwan from in situ-produced cosmogenic nuclides. Earth Surface Processes and Landforms, 30. pp. 955-971. DOI 10.1002/esp.1256

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Abstract

The concentration of cosmogenic nuclides in rocks exposed at the Earth’s surface is proportional to the total duration of their exposure. This is the basis for bedrock surface exposure dating and has been used to constrain valley lowering rates in the Taroko gorge, eastern Central Range, Taiwan. Taroko gorge contains a uniquely complete geomorphic record of fluvial valley lowering: continuous, fluvially sculpted surfaces are present in the lower 200 m of this marble gorge. Assuming no post-fluvial erosion of the gorge wall, the concentration of in situ-produced cosmogenic 36Cl measured in gorge wall marbles reveals exposure ages from 0·2 ka in the active channel to 6·5 ka at 165 m above the present river. These ages imply an average fluvial incision rate of 26 ± 3 mm a−1 throughout the middle and late Holocene. Taking into account lateral gorge wall retreat after initial thalweg lowering would give rise to calculated older exposure ages. Without considering gorge wall retreat, our estimates therefore represent maximum incision rates. Estimated maximum Holocene incision rates are higher than the long-term exhumation rates derived from fission track dating. The longterm gorge development governed by tectonic uplift is superimposed by short-term variations in incision rates caused by climatic or regional tectonic changes.

Item Type: Article
Uncontrolled Keywords: 2005 AREP 2005 P IA49
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title: Earth Surface Processes and Landforms
Volume: 30
Page Range: pp. 955-971
Identification Number: 10.1002/esp.1256
Depositing User: Sarah Humbert
Date Deposited: 18 Aug 2010 15:15
Last Modified: 23 Jul 2013 09:59
URI: http://eprints.esc.cam.ac.uk/id/eprint/1812

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