UNSATURATED ZONE CALCITE 813C EVIDENCE OF SOUTHERN NEVADA CLIMATES DURING THE PAST 9 MILLION YEARS
Yucca Mountain, Nevada, is presently the object of intense study as a potential permanent repository for the Nation's high-level radioactive wastes. The mountain consists of a thick sequence of volcanic tuffs in which the depth to the water table ranges from 500 to 700 meters below the land surface. This thick unsaturated zone (UZ), which would host the projected repository, coupled with the present-day arid to semi-arid environment, is considered a positive argument for the site. Evaluation of the site includes defining the relationship between climate variability, as the input function or driver of site- and regional-scale ground-water flow, and the possible transport and release of radionuclides. Secondary calcite and opal have been deposited in the UZ by meteoric waters that infiltrated through overlying soils and percolated through the tuffs. The oxygen isotopic composition ({delta}{sup 18}O values) of these minerals reflect contemporaneous meteoric waters and the {delta}{sup 13}C values reflect soil organic matter, and hence the resident plant community, at the time of infiltration (Whelan et al., 1994). Recent U/Pb age determinations of opal in these occurrences allows the {delta}{sup 13}C values of associated calcite to be used to reconstruct general climate variations during the past 9 M.y.
- Research Organization:
- Yucca Mountain Project, Las Vegas, NV (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- DE-AC01-91RW00134
- OSTI ID:
- 776502
- Report Number(s):
- MOL.19990812.0387; TRN: US0702876
- Country of Publication:
- United States
- Language:
- English
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