Six untreated whole-rock samples of the Stearns Shale with low Sr87/Sr86 and Rb87/Sr86 ratios define a least squares isochron of 371 ± 15 m.y., with an initial Sr87/Sr86 ratio of 0.7091 ± 0.0015, using a 50 b.y. half-life for Rb87. Treatment of the samples with 2N HC1 with constant agitation for 15 minutes produced the following results: 6 samples of insoluble residue with much higher Sr87/Sr86 and Rb87/Sr86 ratios and a Rb-free leach of low Sr87/ Sr86. Least squares analysis of the insoluble residue samples yields a 276 ± 10 m.y. isochron with initial Sr87/Sr86 of 0.7195 ± 0.0005. This age is close to the presumed age of the Lower Permian and suggests that this method may allow the accurate dating of some predominantly allogenic calcareous shales.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.