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Late quaternary history and uranium isotopic compositions of ground water discharge deposits, Crater Flat, Nevada

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Abstract

Three carbonate-rich spring deposits are present near the southern end of Crater Flat, NV, approximately 18 km southwest of the potential high-level waste repository at Yucca Mountain. We have analyzed five samples of carbonate-rich material from two of the deposits for U and Th isotopic compositions. Resulting U-series disequilibrium ages indicate that springs were active at 18 ?? 1, 30 ?? 3, 45 ?? 4 and >70 ka. These ages are consistent with a crude internal stratigraphy at one site. Identical ages for two samples at two separate sites suggest that springs were contemporaneous, at least in part, and were most likely part of the same hydrodynamic system. In addition, initial U isotopic compositions range from 2.8 to 3.8 and strongly suggest that ground water from the regional Tertiary-volcanic aquifer provided the source for these hydrogenic deposits. This interpretation, along with water level data from near-by wells suggest that the water table rose approximately 80 to 115 m above present levels during the late Quaternary and may have fluctuated repeatedly. Current data are insufficient to allow reconstruction of a detailed depositional history, however geochronological data are in good agreement with other paleoclimatic proxy records preserved throughout the region. Since these deposits are down gradient from the potential repository site, the possibility of higher ground water levels in the future dramatically shortens both vertical and lateral ground water pathways and reduces travel times of transported radionuclides to potential discharge sites.

Additional Publication Details

Publication type:
Conference Paper
Publication Subtype:
Conference Paper
Title:
Late quaternary history and uranium isotopic compositions of ground water discharge deposits, Crater Flat, Nevada
ISBN:
0872629503
Year Published:
1993
Language:
English
Publisher:
Publ by ASCE
Publisher location:
New York, NY, United States
Larger Work Title:
High Level Radioactive Waste Management
First page:
1573
Last page:
1580
Number of Pages:
8
Conference Title:
Proceedings of the 4th Annual International Conference on High Level Radioactive Waste Management
Conference Location:
Las Vegas, NV, USA
Conference Date:
26 April 1993 through 30 April 1993