14C Groundwater Age and the Importance of Chemical Fluxes Across Aquifer Boundaries in Confined Cretaceous Aquifers of North Carolina, USA
dc.contributor.author | Kennedy, Casey D. | |
dc.contributor.author | Genereux, David P. | |
dc.date.accessioned | 2021-02-11T20:58:49Z | |
dc.date.available | 2021-02-11T20:58:49Z | |
dc.date.issued | 2007-01-01 | |
dc.identifier.citation | Kennedy, C. D., & Genereux, D. P. (2007). 14C groundwater age and the importance of chemical fluxes across aquifer boundaries in confined Cretaceous aquifers of North Carolina, USA. Radiocarbon, 49(3), 1181-1203. | |
dc.identifier.issn | 0033-8222 | |
dc.identifier.doi | 10.1017/S0033822200043101 | |
dc.identifier.uri | http://hdl.handle.net/10150/653791 | |
dc.description.abstract | Radiocarbon activity, He concentrations, and other geochemical parameters were measured in groundwater from the confined Black Creek (BC) and Upper Cape Fear (UCF) aquifers in the Coastal Plain of North Carolina. 14C ages adjusted for geochemical and diffusion effects ranged from 400 to 21,900 BP in the BC, and 13,400 to 26,000 BP in the underlying UCF; ages increased coastward in both aquifers. Long-term average linear groundwater velocity is about 2.5 m/yr for the BC, and somewhat larger for the UCF. Aquifer-aquitard exchange is an important influence on the DIC concentration, 14C activity, and estimated age of aquifer groundwater. Accounting for this exchange in 14C age calculations places the groundwater samples with the lowest estimated recharge temperatures nearest in time to the last glacial maximum. Traditional geochemical correction models that do not account for aquifer-aquitard exchange significantly overestimate groundwater age. He concentration in groundwater varies with both age and stratigraphic position. Dissolved He data provide strong evidence of upward vertical He transport through the study aquifers; data from the UCF are broadly consistent with the pattern expected for a confined aquifer receiving a concentrated, localized He flux from below (based on a previously published model for this situation), in this case most likely from crystalline bedrock. He has potential as an indicator of groundwater age in the study aquifers, if interpreted within an appropriate analytical framework that includes the observed strong vertical transport. delta-18O in the oldest groundwater is enriched (relative to modern groundwater) by 1 to 1.2, the opposite of the delta-18O depletion found in many old groundwaters but consistent with the enrichment found in groundwater in this age range in Georgia and Florida. | |
dc.language.iso | en | |
dc.publisher | Department of Geosciences, The University of Arizona | |
dc.relation.url | http://radiocarbon.webhost.uits.arizona.edu/ | |
dc.rights | Copyright © by the Arizona Board of Regents on behalf of the University of Arizona. All rights reserved. | |
dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | |
dc.title | 14C Groundwater Age and the Importance of Chemical Fluxes Across Aquifer Boundaries in Confined Cretaceous Aquifers of North Carolina, USA | |
dc.type | Article | |
dc.type | text | |
dc.identifier.journal | Radiocarbon | |
dc.description.collectioninformation | The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information. | |
dc.eprint.version | Final published version | |
dc.description.admin-note | Migrated from OJS platform February 2021 | |
dc.source.volume | 49 | |
dc.source.issue | 3 | |
dc.source.beginpage | 1181 | |
dc.source.endpage | 1203 | |
refterms.dateFOA | 2021-02-11T20:58:49Z |