Cenomanian-lower Coniacian radiolarian assemblages from the Naiba reference section (Sakhalin)

Reexamination of radiolarians from the Naiba and Bykovo formations of the Naiba reference section (West Sakhalin Mountains) is carried out. Distinguished in the section are the Cromyomma (?) nodosa-Amphipyndax sp. A (terminal early Cenomanian), Cuboctostylus kasinzovae-C. sakhalinensis (Middle Cenomanian), Cuboctostylus trifurcatus-Cassideus yoloensis (terminal middle-late Cenomanian), and Spongodiscus concentricus-Multastrum robustum (late Turonian to early Coniacian probably) assemblages. According to results of comparative analysis for North Pacific regions, concurrent radiolarian assemblages from the Naiba section and California contain up to 40% of species in common, whereas taxonomic similarity with assemblages from Japan is insignifican in contrast.