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Topography and subduction geometry in the central Andes: Clues to the mechanics of a noncollisional orogenThe central Andeean orogen between 12 deg and 32 deg S latitude exhibits a high degree of spatial order: principally an extraordinary bilateral symmetry that is common to the Earth's surface, the underlying Wadati-Benioff zone, and the Nazca/South America plate kinematics, which has been stable since the mid-Tertiary. This spatial order must reflect the physical mechanisms of mountain building in this noncollisional orogen. The shapes of the topography and subduction zone can be reduced to symmetric and antisummeric components relative to any verical symmetry plane; the particular plaen which minimizes the antisymmetry (and maximizes the symmetry) is well resolved and is essentially coincident with the stable Euler equator of Nacza/South America relative motion since the mid-Tertiary. That the topography, subduction geometry, and persistent mid-Tertiary plate kinematics share common spatial and geometric elements suggests that he distribution of topography in this orogen depends strongly on the dynamics of subduction. Other factors that might affect the topography and underlying tectonics, such as climate and inherited strutura fabric, which have different spatial characterisitcs, must be of less significance at a continental scale. Furthermore, the small components of asymmetry among the various elements of the orogen appear to be mutually relate in a simple way; it is possible that this coupled asymmetry is associated with a late Teriary change in plate kinematics. These observations suggest that there is a close connection between plate tectonics and the form of the Earth's surface in this noncollisional setting. It follows hta the distribution of topography near convergent plate boundaries may provide a powerful constraing for understanding the dynamics of subduction.
Document ID
19950057699
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Gephart, John W.
(Cornell University Ithaca, New York, United States)
Date Acquired
August 16, 2013
Publication Date
June 10, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: B6
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
95A89298
Funding Number(s)
CONTRACT_GRANT: NAGW-3338
CONTRACT_GRANT: NSF EAR-88-16287
CONTRACT_GRANT: NSF EAR-88-16630
Distribution Limits
Public
Copyright
Other

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