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dc.contributor.authorTaylor, Claude B.
dc.date.accessioned2021-02-11T21:46:27Z
dc.date.available2021-02-11T21:46:27Z
dc.date.issued2004-01-01
dc.identifier.citationTaylor, C. B. (2004). Time-dependent factors inherent in the age equation for determining residence times of groundwater using 14C: a procedure to compensate for the past variability of 14C in atmospheric carbon dioxide, with application to the Wairau deep aquifer, Marlborough, New Zealand. Radiocarbon, 46(2), 501-515.
dc.identifier.issn0033-8222
dc.identifier.doi10.1017/S0033822200035566
dc.identifier.urihttp://hdl.handle.net/10150/654977
dc.descriptionFrom the 18th International Radiocarbon Conference held in Wellington, New Zealand, September 1-5, 2003.
dc.description.abstractThe radiocarbon concentration of dissolved inorganic carbon in groundwater is most logically and completely represented as the product of 5 time-variable factors; these are mutually independent, and all must be considered and evaluated to determine a groundwater residence time. In the case of one factor, the 14C/(12C+13C) ratio of atmospheric CO2, its time variability can be side-stepped by assuming it to be constant at the pre-bomb 1950 value, and assigning an apparent half-life in the radioactive decay term. Apparent half-lives are calculated here for 5 separate periods extending back to 24,000 BP, working from the INTCAL98 atmospheric calibration. This approach can be extended further back in time when the necessary atmospheric calibrations are updated with greater certainty. The procedure is applied to the recently-explored Wairau Deep Aquifer, underlying central areas of the coastal Wairau Plain, Marlborough. The evolution of dissolved inorganic carbon concentration for this river-recharged groundwater is apparent from distinct trends in 13C, and is confirmed by hydrochemical modelling. Extension to 14C concentrations yields minimum/maximum limits for groundwater residence times to 3 wells. In all 3 cases, the maximum is uncertain due to present uncertainty of the apparent half-life applicable before 24,000 BP. Residence times for the 2 wells closest to the recharge area are at least 17,400 yr, while that for a well further down the aquifer is at least 38,500 yr. Recharge, therefore, occurred during the Otiran glaciation, while the present-day near-surface fluvioglacial deposits of the Wairau Plain were accumulating. Drawdown-recovery records over 3 yr indicate a permeable connection to compensating recharge, enabling limited exploitation for vineyard irrigation.
dc.language.isoen
dc.publisherDepartment of Geosciences, The University of Arizona
dc.relation.urlhttp://radiocarbon.webhost.uits.arizona.edu/
dc.rightsCopyright © by the Arizona Board of Regents on behalf of the University of Arizona. All rights reserved.
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subjectabsolute age
dc.subjectalluvium aquifers
dc.subjectaquifers
dc.subjectAustralasia
dc.subjectC 13 C 12
dc.subjectC 14
dc.subjectcarbon
dc.subjectcase studies
dc.subjectCenozoic
dc.subjectconcentration
dc.subjectcorrections
dc.subjectdates
dc.subjectgeochemistry
dc.subjectground water
dc.subjecthydrochemistry
dc.subjecthydrogen
dc.subjectisotope ratios
dc.subjectisotopes
dc.subjectMarlborough New Zealand
dc.subjectNew Zealand
dc.subjectO 18 O 16
dc.subjectoxygen
dc.subjectprinciples
dc.subjectQuaternary
dc.subjectradioactive isotopes
dc.subjectrecharge
dc.subjectresidence time
dc.subjectSouth Island
dc.subjectstable isotopes
dc.subjecttritium
dc.subjectupper Quaternary
dc.subjectWairau Plain
dc.titleTime-Dependent Factors Inherent in the Age Equation for Determining Residence Times of Groundwater Using 14C: A procedure to Compensate for the Past Variability of 14C in Atmospheric Carbon Dioxide, with Application to the Wairau Deep Aquifer, Marlborough, New Zealand
dc.typeProceedings
dc.typetext
dc.identifier.journalRadiocarbon
dc.description.collectioninformationThe Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information.
dc.eprint.versionFinal published version
dc.description.admin-noteMigrated from OJS platform February 2021
dc.source.volume46
dc.source.issue2
dc.source.beginpage501
dc.source.endpage515
refterms.dateFOA2021-02-11T21:46:27Z


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