Potassium-argon ages of volcanic rocks in Nye and Esmeralda counties, Nevada.

Abstract

K-Ar ages are reported for biotite and sandine from 29 specimens of Tertiary flows and welded tuffs. In the Indian Trail Formation and older Miocene volcanics, range is 18 to 26 m.y.; in the Piapi Canyon Group the age is 10.5 to 16 m.y.; and in the Thirsty Canyon Tuff the age is 6.2 to 7.5 m.y. Precision estimated, by duplicate analysis, comparison on mineral pairs and different localities in welded tuffs, indicate that to distinguish between two rocks at 95 percent confidence level, their ages must differ by 3.4 to 8.5 percent if each rock is dated by a mineral pair. In contrast to chemical diversity of the rocks, K concentrations in biotite and sanidine from each pyroclastic unit are remarkably consistent. Inconsistence in other units may be due to wrong age determinations, miscorrelation, or contamination.

34 samples from this reference