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

Li, Xianglei; Wendt, Kathleen A.; Dublyansky, Yuri; Moseley, Gina E.; Spötl, Christoph; Edwards, R. Lawrence

Uranium–uranium (inline-formula234U–inline-formula238U) disequilibrium dating can determine the age of secondary carbonates over greater time intervals than the well-established inline-formula230Th–inline-formula234U dating method. Yet it is rarely applied due to unknowns in the initial inline-formulaδ234U (inline-formulaδ234Uinline-formulai) value, which result in significant age uncertainties. In order to understand the inline-formulaδ234Uinline-formulai in Devils Hole 2 cave, Nevada, we have determined 110 inline-formulaδ234Uinline-formulai values from phreatic calcite using inline-formula230Th–inline-formula234U disequilibrium dating. The sampled calcite was deposited in Devils Hole 2 between 4 and 590 ka, providing a long-term look at inline-formulaδ234Uinline-formulai variability over time. We then performed multi-linear regression among the inline-formulaδ234Uinline-formulai values and correlative inline-formulaδ18O and inline-formulaδ13C values. The regression can be used to estimate the inline-formulaδ234Uinline-formulai value of Devils Hole calcite based upon its measured inline-formulaδ18O and inline-formulaδ13C values. Using this approach and the measured present-day inline-formulaδ234U values of Devils Hole 2 calcite, we calculated 110 independent inline-formula234U–inline-formula238U ages. In addition, we used newly measured inline-formulaδ18O, inline-formulaδ13C, and present-day inline-formulaδ234U values to calculate 10 inline-formula234U–inline-formula238U ages that range between 676 and 731 ka, thus allowing us to extend the Devils Hole chronology beyond the inline-formula230Th–inline-formula234U-dated chronology while maintaining an age precision of inline-formula∼ 2 %. Our results indicate that calcite deposition at Devils Hole 2 cave began no later than 736 inline-formula± 11 kyr ago. The novel method presented here may be applied to future speleothem studies in similar hydrogeological settings, given appropriate calibration studies.

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Li, Xianglei / Wendt, Kathleen A. / Dublyansky, Yuri / et al: Novel method for determining 234U–238U ages of Devils Hole 2 cave calcite (Nevada). 2021. Copernicus Publications.

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