Uranium-thorium dating of quaternary carbonate accumulations in the Nevada Test Site region, southern Nevada
A useful way to approach the problem of tectonic activity in an arid region is through study of the history of movement of faults and fractures and of the young alluvial material they displace. Easily datable materials are scarce in these deposits, but carbonates such as caliche, calcrete, travertine, calcite vein, and tufa are common. Several types of these carbonates from the Nevada Test Site area in the southern Great Basin have been collected and dated by the uranium-series method. A variety of geologic settings are represented. The carbonate samples were subjected to a complex treatment process, and the resulting preparations were counted on an alpha spectrometer. Some of the samples from obviously closed systems yielded reasonable ages; others gave only a minimum age for a material or event. Many of the ages obtained agree well with estimates of age determined from dated volcanic units, fault-scarp morphology, and displaced alluvial units. Among the significant ages obtained were three dates of greater than 400,000 years on calcite-filling fractures above and below the water table in an exploratory drill hole for a possible candidate nuclear waste repository site at Yucca Mountain. Another date on calcrete from immediately below the youngest basalt in the region gave an age of 345,000 years, which agrees extremely well with the K-Ar age determined for the basalt of about 300,000 years. Undisturbed travertine that fills faults in several areas gave ages from about 75,000 years to greater than 700,000 years. Soil caliche and calcretes slightly displaced or broken by repeated movement on faults gave minimum ages in the range from more than 5000 to more than about 25,000 years.
- Research Organization:
- Geological Survey, Denver, CO (United States); Denver Univ., CO (United States)
- DOE Contract Number:
- AI08-78ET44802
- OSTI ID:
- 59633
- Report Number(s):
- USGS-OFR--81-119
- Country of Publication:
- United States
- Language:
- English
Similar Records
Uranium-series dating of secondary carbonate and silica precipitates relating to fault movements in the Nevada Test Site region and of caliche and travertine samples from the Amargosa Desert
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Related Subjects
58 GEOSCIENCES
AGE ESTIMATION
ALPHA SPECTROSCOPY
CALCITE
CALCRETES
CARBONATES
EXPERIMENTAL DATA
GEOLOGY
ISOTOPE DATING
ISOTOPE RATIO
NEVADA TEST SITE
RADIOACTIVE WASTE DISPOSAL
TECTONICS
THORIUM 230
THORIUM 232
THORIUM ISOTOPES
TRAVERTINE
TUFF
UNDERGROUND DISPOSAL
URANIUM 234
URANIUM 238
URANIUM ISOTOPES
Yucca Mountain Project