FIRST RESULTS OF U−Th/He DATING OF EPIGENETIC PYRITE FROM ROCKS OF THE BAZHENOV FORMATION, WESTERN SIBERIA

U–Th/He method was applied to determine the age of epigenetic pyrite from the oil source rocks of the Bazhenov Formation, Western Siberia. Results indicate the possibility to date the post-sedimentation processes in a sedimentary basin by authigenic pyrite U–Th/He dating. The U–Th/He isochron age of pyrite (n = 7) from the dolomites of the Bazhenov Formation within the Frolovskaya megadepression is much younger than the age of sedimentation and corresponds to the Santonian-Cenomanian stages of the Upper Cretaceous (90 ± 8 Ma).