Rb-Sr dating on the rocks in Japan (I),

Abstract

Abstract: Geologic age measurements with the Rb-Sr method were made on micas and feldspars separated from granites, granite pegmatites, gneisses and schists of the South Western part of Japan. And the results indicate that the time of the igneous and metamorphic activities represented by these rocks are divided into five geologic periods: 1. Silurian 406-443 my 2. Some uncertain period older than 269 my 3. Early Jurassic 175-196 my 4. Upper Cretaceous 63-114 my 5. Tertiary 12-35 my