EGU21-1955
https://doi.org/10.5194/egusphere-egu21-1955
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Novel method for determining 234U-238U ages of Devils Hole 2 cave calcite (Nevada)

Xianglei Li1, Kathleen A. Wendt1,2, Yuri Dublyansky2, Gina E. Moseley2, Christoph Spötl2, and R. Lawrence Edwards1
Xianglei Li et al.
  • 1Department of Earth Sciences, University of Minnesota, 116 Church Street SE, Minneapolis 55455, USA
  • 2Institute of Geology, University of Innsbruck, Innrain 52, Innsbruck, Austria

Uranium-uranium (234U-238U) disequilibrium dating can determine the age of secondary carbonates over greater time intervals than the well-established 230Th-234U dating method. Yet it is rarely applied due to unknowns in the initial d234U (d234Ui) value, which result in significant age uncertainties. In order to understand the d234Ui in Devils Hole 2 cave, Nevada, we have determined 110 d234Ui values from phreatic calcite using 230Th-234U disequilibrium dating. The sampled calcite was deposited in Devils Hole 2 between 4 and 590 ka, providing a long-term look at d234Ui variability over time. We then performed multi-linear regression among the d234Ui values and correlative d18O and d13C values. The regression can be used to estimate the d234Ui value of Devils Hole calcite based upon its measured d18O and d13C values. Using this approach and the measured present-day d234U values of Devils Hole 2 calcite, we calculated 110 independent 234U-238U ages. In addition, we used newly measured d18O, d13C, and present-day d234U values to calculate 10 234U-238U ages that range between 676 and 731 ka, thus allowing us to extend the Devils Hole chronology beyond the 230Th-234U-dated chronology while maintaining an age precision of ~2 %. Our results indicate that calcite deposition at Devils Hole 2 cave began no later than 736 ± 11 kyr ago. The novel method presented here may be applied to future speleothem studies in similar hydrogeological settings, given appropriate calibration studies.

How to cite: Li, X., Wendt, K. A., Dublyansky, Y., Moseley, G. E., Spötl, C., and Edwards, R. L.: Novel method for determining 234U-238U ages of Devils Hole 2 cave calcite (Nevada), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1955, https://doi.org/10.5194/egusphere-egu21-1955, 2021.

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