Growth of South Rough Ridge, Central Otago, New Zealand: using in situ cosmogenic isotopes and geomorphology to study an active, blind reverse fault

Bennett, E. R. and Youngson, J. H. and Jackson, J. A. and Norris, R. J. and Raisbeck, G. M. and Yiou, F. and Fielding, E. (2005) Growth of South Rough Ridge, Central Otago, New Zealand: using in situ cosmogenic isotopes and geomorphology to study an active, blind reverse fault. Journal of Geophysical Research, 110. B02404. DOI 10.1029/2004JB003184

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Official URL: http://dx.doi.org/10.1029/2004JB003184

Abstract

In situ cosmogenic 10Be and 26Al measurements on sedimentary quartzites, together with analysis of abandoned river terraces, can be used to show how drainage responded to the lateral propagation of a late Quaternary anticline forming above a blind reverse fault in Central Otago, New Zealand. A close link between the progression of cosmogenic ages and the tectonic geomorphology allows us to confirm that uplift and propagation rates on the anticline are in the ranges 0.08–0.12 mm yr−1 and 0.8–1.5 mm yr−1, respectively, over the last 550,000 years. The agreement between the isotopic and geomorphological evidence in turn requires that minimum 10Be exposure ages as great as 660 ka are not in steady state with respect to erosion. This is a geochemical result of significance, as it opens the possibility of a more regional analysis of landscape evolution in this region, using the same rocks. On an adjacent anticline, thought to be even older on geomorphological arguments, 10Be concentrations give minimum exposure ages in the range 750–1400 ka. These extremely old minimum ages are rare worldwide, as they are usually limited to smaller values by erosion. They are attributable to the very resistant nature of the quartz-rich boulders in which the measurements were made, which in places are shown to have erosion rates lower than 0.5 mm kyr−1.

Item Type: Article
Additional Information: Copyright 2005 by the American Geophysical Union.
Uncontrolled Keywords: 2005 PUBL; 2005 AREP; IA46; IA47
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
08 - Green Open Access
Journal or Publication Title: Journal of Geophysical Research
Volume: 110
Page Range: B02404
Identification Number: 10.1029/2004JB003184
Depositing User: Sarah Humbert
Date Deposited: 12 Sep 2011 15:03
Last Modified: 10 Jul 2014 12:08
URI: http://eprints.esc.cam.ac.uk/id/eprint/1579

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