Affiliation:
1. Institute of Geology, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria
2. Department of Earth Sciences, University of Minnesota, 116 Church St. SE, Minneapolis, Minnesota 55455, USA
Abstract
Abstract
Subaqueous calcite deposited on the walls of Devils Hole 2 cave (Nevada, USA) represents a unique archive for geochemical variations within the regional aquifer. Here, we present a 475,000-year record of initial 234U/238U activity ratios in delta notation (δ234U0). Results show a range in values from 1851–1616‰. Variations in δ234U0 coincide with interglacial-glacial cycles over the past 475,000 years. Maximum δ234U0 values correspond to the last five glacial intervals, during which southwest Nevada experienced cool, pluvial conditions. Minimum δ234U0 values correspond to interglacial intervals, during which this region experienced warm, arid conditions. We propose that an elevated water table during glacial periods inundated previously dry bedrock and basin sediments, thereby leaching excess 234U accumulated in these materials. We interpret Devils Hole 2 cave δ234U0 as a proxy for water-rock interactions in this regional aquifer, which is ultimately tied to the surface moisture conditions at recharge zones. The mechanism proposed here serves as a testable hypothesis and possible analogue for future subaqueous speleothem studies in similar hydrogeologic settings. Due to its unprecedented duration, the Devils Hole 2 cave δ234U0 record provides the first paleo-moisture record in southwest Nevada for marine isotope stages 10–12. In addition, high-precision δ234U measurements of modern groundwaters sampled from Devils Hole 2 cave are presented.
Publisher
Geological Society of America
Reference73 articles.
1. 234U/238U activity ratios of dissolved uranium in groundwaters from some Triassic sandstones in England;Andrews;Chemical Geology,1982
2. Petrography, strontium, barium and uranium concentrations, and strontium and uranium isotope ratios in speleothems as paleoclimate proxies: Soreq Cave, Israel;Ayalon;The Holocene,1999
3. Last glacial maximum Holocene lake levels of Owens Lake, eastern California, USA;Bacon;Quaternary Science Reviews,2006
4. Death Valley regional groundwater flow system, Nevada and California: Hydrogeologic framework and transient groundwater flow model;Belcher;U.S. Geological Survey Professional Paper,2010
5. Insights from a synthesis of old and new climate-proxy data from the Pyramid and Winnemucca lake basins for the period 48 to 11.5 cal ka;Benson;Quaternary International,2013
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