The LA-ICP-MS U-Pb Ages of Detrital Zircons from Sedimentary Rocks of the Komsomolskaya Group (Northern Sikhote-Alin)

A geochronological study of detrital zircons from sedimentary rocks of the Gorinskaya (91 zircons with concordant ages), Pionerskaya (117 zircons with concordant ages), and Pivanskaya (115 zircons with concordant ages) formations of the Komsomolskaya Group has been carried out. It was found that the Pb-206/U-238 age of the youngest zircon population is consistent with the stratigraphic age only for the Pivanskaya Formation. For the other two formations, the youngest zircon populations turned out to be significantly younger than their upper stratigraphic limits. New evidence shows that: (1) the age of the "Berriasian-Valanginian" sediments of the Pionerskaya Formation is not older than the Barremian and (2) the age of the "Tithonian-Berriasian" deposits of the Gorinskaya Formation is not older than the Hauterivian. The subdivision of the Komsomolskaya Group into formations is based primarily on lithological criteria. However, since the composition of the formations is very similar, the identical deposits in other Lower Cretaceous sequences of the region could be assigned to other stratigraphic units. Thus, the above conclusion is valid only for the sections we studied.