New Zealand Journal of Geology and Geophysics abstracts
Combining geomorphic observations with in situ
cosmogenic isotope measurements to study anticline growth and fault
propagation in Central Otago, New Zealand
Eleanor Bennett1
John Youngson2
James Jackson1*
Richard Norris2
Grant Raisbeck3
Françoise Yiou3
1Bullard
Laboratories
Madingley Road
Cambridge CB3 0EZ, United Kingdom
2Department
of Geology
University of Otago
P.O. Box 56
Dunedin, New Zealand
3Centre
de Spectrométrie Nucléaire et
de Spectrométrie
de Masse
IN2P3-CNRS
Bâtiment 108, 91405 Orsay, France
*Corresponding
author: jackson@esc.cam.ac.uk
Abstract Measurements of
10Be concentrations in quartz-rich boulders
exposed by the uplift of anticlinal ranges in Central Otago, New
Zealand, are used to investigate the fault propagation styles and rates
for the underlying blind reverse faults. 10Be
ages along Little Rough Ridge reveal the propagation rate for this
fault to be between zero (i.e., not propagating at all, if the ages
reflect emergence of a fault of fixed length through a sloping surface)
and a maximum of 8.1 mm/yr, if the ages reflect true lateral
growth. Regardless of the propagation rate, Little Rough Ridge has
established its length rapidly compared with the rate at which it has
accumulated displacement. On Raggedy Range, the 10Be
ages, together with structural data, imply that the ridge reached its
current length by the merging of several small fault segments. This
study emphasises the importance of combining 10Be
measurements with geomorphic observations. Without understanding the
geomorphological context, 10Be exposure ages
are difficult to interpret at all; but even with geomorphic data, the
interpretation of these ages can still be ambiguous.
Keywords fault
propagation; 10Be; dating; drainage evolution;
wind gaps; neotectonics
G05022; Received 16 May 2005; accepted 9 February 2006; Online
publication date 12 May 2006
New Zealand Journal of Geology & Geophysics, 2006,
Vol. 49: 217–231
0028–8306/06/4902–0217 ©
The Royal Society of New Zealand 2006
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