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Regional exhumation history of brittle crust during subduction initiation, Fiordland, southwest New Zealand, and implications for thermochronologic sampling and analysis strategies

Sutherland, Rupert and Gurnis, Michael and Kamp, Peter J. J. and House, Martha A. (2009) Regional exhumation history of brittle crust during subduction initiation, Fiordland, southwest New Zealand, and implications for thermochronologic sampling and analysis strategies. Geosphere, 5 (5). pp. 409-425. ISSN 1553-040X. https://resolver.caltech.edu/CaltechAUTHORS:20091019-120125321

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[img] Video (MPEG) (Animation 1 - Animated best-fitting model of Fiordland rock uplift as a function of time R(t)) - Supplemental Material
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[img] Video (MPEG) (Animation 2 - Animation model of Fiordland rock uplift rate as a function of time, R′(t)) - Supplemental Material
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Abstract

We analyze spatial trends and statistical properties of 410 apatite and zircon fission track and (U-Th)/He ages, and implement a weighted least-squares regression scheme to obtain the regional rock uplift history associated with subduction initiation beneath Fiordland, New Zealand. We observe the onset of rapid exhumation at 25–15 Ma in southwest Fiordland, immediately following a time of significant change in regional plate motions. During the period 15–5 Ma, the locus of rapid exhumation broadened and migrated toward the northeast at ~30% of the plate motion rate, but exhumation remained localized along the northwest margin. Since 5 Ma, the zone of rapid exhumation has become broader, and the present high-amplitude gravity and topographic anomalies are spatially associated with the most tightly folded part of the subducted slab. We suggest that the pattern of exhumation tracks the along-strike and downdip development of the subducted slab, which requires tectonic erosion of mantle lithosphere of the overriding plate. Based upon local patterns of age variability, we hypothesize that brittle faults have displaced and rotated equal-cooling-age surfaces, and that there is short-wavelength (<10 km) spatial correlation between faults and topographic features. Our regression method allows us to simultaneously consider implications of all age data, evaluate “geological noise” introduced by brittle faults, and make cooling age predictions at any point in the region. The residuals from our regression indicate that, on average, mountain tops in Fiordland have undergone slightly greater rock uplift than adjacent valleys, even though our data are too sparse to identify specific faults. We suggest that sampling programs in active tectonic settings such as Fiordland must be sufficiently dense to determine both mean exhumation history and regional geological variability associated with faults.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1130/GES00225.1 DOIArticle
http://geosphere.gsapubs.org/content/5/5/409PublisherArticle
ORCID:
AuthorORCID
Gurnis, Michael0000-0003-1704-597X
Additional Information:© 2009 Geological Society of America. Received 8 January 2009. Revision received 1 July 2009. Accepted 27 July 2009. We thank Lawrence Gaylor, Xu Ganqing, Ian Whitehouse, and Ivan Liddell for fi ssion track sample collection and technical assistance in the University of Waikato Fission Track Laboratory; K. Gallacher and T. Ehlers for providing software that calculated model thermochronologic ages from thermal histories; Simon Cox and Andy Nicol for reviews of an early draft; and Randy Keller, David Shuster, and two anonymous reviewers. This paper is contribution 10,011 of the Division of Geological and Planetary Sciences and 94 of the Tectonics Observatory, Caltech. It was funded by the NZ Marsden Fund and the US National Science Foundation. * Supplemental File 1 - This is a Microsoft Word doc containing Figure S1 and the thermochronologic data table used to compute the regional exhumation history. This can also be accessed by visiting http://dx.doi.org/10.1130/GES00225.S1. * Animation 1 - Animated best-fitting model of Fiordland rock uplift as a function of time R(t). You will need VLC media player, which can be downloaded at www.videolan.org/vlc, or another multimedia player to view the animation. This file can also be reached at http://dx.doi.org/10.1130/GES00225.SA1. * Animation 2 - Animation model of Fiordland rock uplift rate as a function of time, R′(t). You will need VLC media player or another multimedia player to view the animation. This file can also be reached at http://dx.doi.org/10.1130/GES00225.SA2.
Group:Caltech Tectonics Observatory, Seismological Laboratory
Funders:
Funding AgencyGrant Number
New Zealand Marsden FundUNSPECIFIED
NSFUNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Tectonics Observatory77
Caltech Tectonics Observatory94
Issue or Number:5
Record Number:CaltechAUTHORS:20091019-120125321
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20091019-120125321
Official Citation:Rupert Sutherland, Michael Gurnis, Peter J. J. Kamp, and Martha A. House. Regional exhumation history of brittle crust during subduction initiation, Fiordland, southwest New Zealand, and implications for thermochronologic sampling and analysis strategies. Geosphere October 2009, v. 5, p. 409-425, doi:10.1130/GES00225.1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16382
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:26 Oct 2009 19:28
Last Modified:03 Oct 2019 01:11

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