Uranium-trend dating of Quaternary deposits in the Nevada Test Site area, Nevada and California

摘要: The uranium-trend dating method has been used to estimate the ages of alluvium, colluvium, altered volcanic ash, and eolian deposits in Nevada Test Site area. For 5000 800,000 years age, open-system technique consists determining a linear trend from analyses four ten channel samples collected at different depths depositional unit, or soil profile formed unit. concentrations {sup 238}U, 234}U, 230}Th, 232}Th are accurately determined for each sample where made on subsamples less-than-2-mm-size fraction. Isotopic by alpha spectrometry utilizing radioisotope dilution techniques. Analyses 36 suites included this report; U-trend dates were 31 these establishing age ranges deposition stratigraphic units Site. Median indicate 40 +- 15 Ka Q2a sediments, 170 Q2b 270 50 younger Q2c unit 440 60 older Q2s range about 200 500 Ka. Uranium-trend agesmore » laminar carbonate time strong calcium development rather than their host sediments. 19 refs., 35 figs., 5 tabs.« less