Persistent Link:
http://hdl.handle.net/10150/296088
Title:
Subsurface Production of Chlorine-36 and Its Impact on Ground Water Dating
Author:
Kuhn, Mark W.; Davis, Stanley N.; Zito, Richard; Bentley, Harold W.
Affiliation:
University of Arizona, Tucson, Arizona
Issue Date:
16-Apr-1983
Rights:
Copyright ©, where appropriate, is held by the author.
Collection Information:
This article is part of the Hydrology and Water Resources in Arizona and the Southwest collections. Digital access to this material is made possible by the Arizona-Nevada Academy of Science and the University of Arizona Libraries. For more information about items in this collection, contact anashydrology@gmail.com.
Publisher:
Arizona-Nevada Academy of Science
Journal:
Hydrology and Water Resources in Arizona and the Southwest
Abstract:
Chlorine-36 is an important radioisotope with which to date old ground water. The initial chlorine-36 in ground water originates in the atmosphere by cosmic ray spallation of argon-40. Following precipitation and infiltration processes, the natural decay of this radioisotope is then used to date ground water. One must consider, however, the production of chlorine-36 in the subsurface. The production reaction of most interest is ³⁵C1 + neutron → ³⁶C1 + gamma. Buildup of chlorine-36 in the subsurface can result from cosmic ray secondary neutrons near the surface and natural radioactivity produced neutrons below the surface. These production mechanisms, if not taken into consideration, will contribute to the error in chlorine-36 age determinations. To predict subsurface production rates, field measurements were made of thermal neutron fluxes for various geologic materials and depths below the surface. Thermal neutron fluxes were found to vary by more than three orders of magnitude. Theoretical calculations of neutron flux were compared to filed measurements. Estimates of chlorine-36 production rates were then calculated and compared to measured values of chlorine-36 in very old ground water, where decay rates have been hypothesized to be equal to production rates.
Keywords:
Hydrology -- Arizona.; Water resources development -- Arizona.; Hydrology -- Southwestern states.; Water resources development -- Southwestern states.
ISSN:
0272-6106

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleSubsurface Production of Chlorine-36 and Its Impact on Ground Water Datingen_US
dc.contributor.authorKuhn, Mark W.en_US
dc.contributor.authorDavis, Stanley N.en_US
dc.contributor.authorZito, Richarden_US
dc.contributor.authorBentley, Harold W.en_US
dc.contributor.departmentUniversity of Arizona, Tucson, Arizonaen_US
dc.date.issued1983-04-16-
dc.rightsCopyright ©, where appropriate, is held by the author.-
dc.description.collectioninformationThis article is part of the Hydrology and Water Resources in Arizona and the Southwest collections. Digital access to this material is made possible by the Arizona-Nevada Academy of Science and the University of Arizona Libraries. For more information about items in this collection, contact anashydrology@gmail.com.en_US
dc.publisherArizona-Nevada Academy of Scienceen_US
dc.identifier.journalHydrology and Water Resources in Arizona and the Southwesten_US
dc.description.abstractChlorine-36 is an important radioisotope with which to date old ground water. The initial chlorine-36 in ground water originates in the atmosphere by cosmic ray spallation of argon-40. Following precipitation and infiltration processes, the natural decay of this radioisotope is then used to date ground water. One must consider, however, the production of chlorine-36 in the subsurface. The production reaction of most interest is ³⁵C1 + neutron → ³⁶C1 + gamma. Buildup of chlorine-36 in the subsurface can result from cosmic ray secondary neutrons near the surface and natural radioactivity produced neutrons below the surface. These production mechanisms, if not taken into consideration, will contribute to the error in chlorine-36 age determinations. To predict subsurface production rates, field measurements were made of thermal neutron fluxes for various geologic materials and depths below the surface. Thermal neutron fluxes were found to vary by more than three orders of magnitude. Theoretical calculations of neutron flux were compared to filed measurements. Estimates of chlorine-36 production rates were then calculated and compared to measured values of chlorine-36 in very old ground water, where decay rates have been hypothesized to be equal to production rates.en_US
dc.subjectHydrology -- Arizona.en_US
dc.subjectWater resources development -- Arizona.en_US
dc.subjectHydrology -- Southwestern states.en_US
dc.subjectWater resources development -- Southwestern states.en_US
dc.identifier.issn0272-6106-
dc.identifier.urihttp://hdl.handle.net/10150/296088-
dc.identifier.journalHydrology and Water Resources in Arizona and the Southwesten_US
dc.typetexten_US
dc.typeProceedingsen_US
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