Empirically determined uncertainty in potassium-argon ages for Plio-Pleistocene basalts from Crater Flat, Nye County, Nevada

Six samples of basalt from each of four sites in Crater Flat, Nye County, Nevada, were dated by potassium-argon isotopic methods, by each of three separate geochronology laboratories. The mean ages of the four sites range from about 0.4 my (million years) to 4.0 my. The standard error of an age is 0.16 my, regardless of age. Variation among the reported ages can be attributed to aliquot, sample, and interlaboratory differences, with the latter two being dominant. The standard deviation of an age for a single sample dated by one laboratory is estimated as 0.34 my. Overall, the results indicate that Quaternary basalts with approximately 1.5% potassium content can be assigned an age at 90% confidence to within an interval of about 1 my if multiple samples are dated by several laboratories. If only one sample is dated by a single laboratory, the interval increases to about 1.4 my