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Apatite ^4He/^3He and (U-Th)/He Evidence for an Ancient Grand Canyon

Flowers, R. M. and Farley, K. A. (2012) Apatite ^4He/^3He and (U-Th)/He Evidence for an Ancient Grand Canyon. Science, 338 (6114). pp. 1616-1619. ISSN 0036-8075. doi:10.1126/science.1229390.

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The Grand Canyon is one of the most dramatic features on Earth, yet when and why it was carved have been controversial topics for more than 150 years. Here, we present apatite ^4He/^3He thermochronometry data from the Grand Canyon basement that tightly constrain the near-surface cooling history associated with canyon incision. ^4He/^3He spectra for eastern Grand Canyon apatites of differing He date, radiation damage, and U-Th zonation yield a self-consistent cooling history that substantially validates the He diffusion kinetic model applied here. Similar data for the western Grand Canyon provide evidence that it was excavated to within a few hundred meters of modern depths by ~70 million years ago (Ma), in contrast to the conventional model in which the entire canyon was carved since 5 to 6 Ma.

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Farley, K. A.0000-0002-7846-7546
Additional Information:© 2012 American Association for the Advancement of Science. Received 27 August 2012; accepted 7 November 2012. Published online 29 November 2012. This work was supported by NSF grant EAR-1019896 to K.A.F. The data reported in this paper are tabulated in the supplementary materials. We thank B. Wernicke for discussion.
Issue or Number:6114
Record Number:CaltechAUTHORS:20130118-104945109
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36477
Deposited By: Tony Diaz
Deposited On:22 Jan 2013 23:58
Last Modified:09 Nov 2021 23:22

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