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Post–10 Ma uplift and exhumation of the northern Coast Mountains, British Columbia

Farley, K. A. and Rusmore, M. E. and Bogue, S. W. (2001) Post–10 Ma uplift and exhumation of the northern Coast Mountains, British Columbia. Geology, 29 (2). pp. 99-102. ISSN 0091-7613. doi:10.1130/0091-7613(2001)029<0099:PMUAEO>2.0.CO;2.

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Apatite (U-Th)/He ages reveal three distinct periods in the exhumation history of the northern Coast Mountains (∼54°N). A well-developed helium partial retention zone indicates little or no exhumation between ca. 30 and 10 Ma. Beginning at 10 Ma and extending to at least 4 Ma the range underwent steady but slow exhumation of ∼0.22 mm/yr, after which the exhumation rate increased by at least 70%. An 85-km-long He age traverse across the orogen at sea level shows that vertical offsets on post-10 Ma faults are minor. Furthermore, the sea-level He ages (14–2.8 Ma) inversely correlate with local mean elevation along the traverse. These data suggest that the Coast Mountains first appeared as a significant topographic feature only within the past few million years. This history is not consistent with suggestions that uplift of the range resulted from formation of the Queen Charlotte basin in early-middle Miocene time. We speculate that intense erosion by alpine and continental glaciation after 2.5 Ma triggered isostatic uplift and creation of the modern topography of the Coast Mountains.

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Farley, K. A.0000-0002-7846-7546
Additional Information:© 2001 Geological Society of America. Manuscript received May 26, 2000. Revised manuscript received October 12, 2000. Manuscript accepted October 26, 2000. We thank P. Molnar and P. Umhoefer for helpful reviews, R.S. Anderson, M. House, G. Woodsworth, and P. O’Sullivan for discussions, L. Hedges for careful analytical work, and K. Dodson, R. Karpilo, and J. Robinson for field assistance. G. Woodsworth led sample collection on Mount Elizabeth. This work was supported by National Science Foundation grants EAR-9805124 and EAR-9807740.
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Subject Keywords:uplift, Coast Mountains, helium age, exhumation, apatite
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Data Repository item 200115
Issue or Number:2
Record Number:CaltechAUTHORS:20130212-141652973
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Official Citation: K.A. Farley, M.E. Rusmore, and S.W. Bogue Post–10 Ma uplift and exhumation of the northern Coast Mountains, British Columbia Geology, February, 2001, v. 29, p. 99-102, doi:10.1130/0091-7613(2001)029<0099:PMUAEO>2.0.CO;2
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36884
Deposited By: Tony Diaz
Deposited On:27 Feb 2013 22:49
Last Modified:09 Nov 2021 23:25

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