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Published October 1997 | public
Journal Article

Cenozoic thermal evolution of the central Sierra Nevada, California, from (U-Th)/He thermochronometry

Abstract

Apatite(U-Th)/He cooling ages are reported for igneous apatite samples from the central Sierra Nevada and compared to published apatite fission track ages and track length data from the same mineral separates. Helium ages are youngest at low elevations and increase systematically toward higher elevations, ranging from 43 to 84 Ma at Yosemite Valley, 32 to 74 Ma at Kings River Canyon, and 23 to 75 Ma at Mt. Whitney. Helium ages from high elevation samples are generally concordant with corresponding fission track ages, while lower elevation helium ages are substantially younger. Cooling histories inferred from present laboratory derived fission track annealing and helium diffusion models do not match well, suggesting that either helium diffusion rates or fission track annealing rates are miscalibrated at temperatures below about 60°C for geologic exposure periods. Unlike the fission track results, the helium data do not indicate a very low geothermal gradient in the Sierra Nevada during early to middle Tertiary time.

Additional Information

© 1997 Elsevier Science B.V. Received 28 March 1997; revised 10 July 1997; accepted 10 July 1997. This study was supported by National Science Foundation grants EAR-9526895, awarded to B. Wernicke, K. Farley, and J. Saleeby and EAR-9417939 to T. Dumitru. Constructive criticism by S. Peacock. C. Naeser, and an anonymous reviewer substantially improved the presentation of this manuscript. [MK]

Additional details

Created:
August 22, 2023
Modified:
October 20, 2023