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Krypton-81 dating constrains timing of deep groundwater flow activation
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  • Ji-Hyun Kim,
  • Grant Ferguson,
  • Mark Austin Person,
  • Wei Jiang,
  • Zheng-Tian Lu,
  • Florian Ritterbusch,
  • Guo-Min Yang,
  • Rebecca Louise Tyne,
  • Lydia Bailey,
  • Chris J Ballentine,
  • Peter W Reiners,
  • Jennifer C. McIntosh
Ji-Hyun Kim
University of Arizona

Corresponding Author:[email protected]

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Grant Ferguson
University of Saskatchewan
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Mark Austin Person
New Mexico Tech
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Wei Jiang
University of Science and Technology of China
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Zheng-Tian Lu
University of Science and Technology of China
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Florian Ritterbusch
University of Science and Technology of China
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Guo-Min Yang
University of Science and Technology of China
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Rebecca Louise Tyne
University of Oxford
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Lydia Bailey
University of Arizona
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Chris J Ballentine
University of Oxford
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Peter W Reiners
University of Arizona
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Jennifer C. McIntosh
Department of Hydrology and Atmospheric Sciences, University of Arizona
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Abstract

Krypton-81 dating provides new insights into the timing, mechanisms, and extent of meteoric flushing versus retention of saline fluids in the subsurface in response to changes in geologic and/or climatic forcings over 50 ka to 1.2 Ma year timescales. Remnant Paleozoic seawater-derived brines (2-2.5 km depth) associated with evaporites in the Paradox Basin, Colorado Plateau, are beyond the 81Kr dating range (>1.2 Ma) and have likely been preserved due to negative fluid buoyancy and low permeability. 81Kr dating of formation waters above the evaporites indicates topographically-driven meteoric recharge (0.03-0.8 Ma) and salt dissolution since the Late Pleistocene. Formation waters below the evaporites, in basal aquifers, contain relatively young meteoric water components (0.4-1.1 Ma based on 81Kr) that partially flushed remnant brines and dissolved evaporites. We demonstrate that recent, rapid denudation of the Colorado Plateau (<4-10 Ma) activated deep, basinal-scale flow systems as recorded in 81Kr groundwater age distributions.