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Deformation of continental crust along a transform boundary, Coast Mountains, British Columbia

Rusmore, Margaret E. and Bogue, Scott W. and Dodson, Karen and Farley, Kenneth A. and Woodsworth, Glenn J. (2010) Deformation of continental crust along a transform boundary, Coast Mountains, British Columbia. Tectonics, 29 . Art. No. TC4007 . ISSN 0278-7407.

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New structural, paleomagnetic, and apatite (U-Th)/He results from the continental margin inboard of the Queen Charlotte fault (~54°N) delineate patterns of brittle faulting linked to transform development since ~50 Ma. In the core of the orogen, ~250 km from the transform, north striking, dip-slip brittle faults and vertical axis rotation of large crustal domains occurred after ~50 Ma and before intrusion of mafic dikes at 20 Ma. By 20 Ma, dextral faulting was active in the core of the orogen, but extension had migrated toward the transform, continuing there until <9 Ma. Local tilting in the core of the orogen is associated with glacially driven, post-4 Ma exhumation. Integration with previous results shows that post-50 Ma dextral and normal faulting affected a region ~250 km inboard of the transform and ~300 km along strike. Initially widespread, the zone of active extension narrowed and migrated toward the transform ~25 Ma after initiation of the transform, while dextral faulting continued throughout the region. Differential amounts of post-50 Ma extension created oroclines at the southern and northern boundaries of the deformed region. This region approximately corresponds to continental crust that was highly extended just prior to transform initiation. Variation in Neogene crustal tilts weakens interpretations relying on uniform tilting to explain anomalous paleomagnetic inclinations of mid-Cretaceous plutons. Similarities to the Gulf of California suggest that development of a transform in continental crust is aided by previous crustal extension and that initially widespread extension narrows and moves toward the transform as the margin develops.

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Farley, Kenneth A.0000-0002-7846-7546
Additional Information:© 2010 by the American Geophysical Union. Received 23 March 2009; accepted 2 March 2010; published 17 July 2010. This research was supported by NSF awards EAR 0310011, 9805124, and 9807740. We are grateful to all who helped us in the field: Bill Robinson provided excellent logistical support, and help from our field assistants Shannon Shula, Juliet Robinson, and Ron Karpilo was invaluable. Discussions with Carol Evenchick, George Gehrels, Lincoln Hollister, James Haggart, and Paul Umhoefer have shaped our thoughts on this topic over the years. Reviews by Associate Editor Paul Kapp and Michael Oskin greatly improved the manuscript.
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NSFEAR 0310011
Record Number:CaltechAUTHORS:20100809-094819405
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Official Citation:Rusmore, M. E., S. W. Bogue, K. Dodson, K. A. Farley, and G. J. Woodsworth (2010), Deformation of continental crust along a transform boundary, Coast Mountains, British Columbia, Tectonics, 29, TC4007, doi:10.1029/2009TC002502.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19336
Deposited By: Tony Diaz
Deposited On:09 Aug 2010 21:12
Last Modified:03 Mar 2020 13:01

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