A Rb-Sr whole rock isochron based on six samples of Nordagutu granite defines a Permian age of 284 ± 7 (2?) m.y. and an initial 87Sr/86Sr ratio of 0.7044 ± 2 (2?). This granite, intruding Precambrian rocks just outside the southwestern corner of the Oslo Region, is interpreted as cogenetic with the main plutonic series of the Oslo Region.
Rb-Sr whole rock dating of the Nordagutu granite, Oslo Region, Norway