New finds of middle and late jurassic radiolarians in the siliceous-clayey and clastic rocks of the Nadan’khada-Bikin terrane (Jurassic accretionary wedge, western Sikhote Alin) and their geological significance

Abstract

The lithostratigraphic analysis of the paleooceanic sediments in the Bikin segment of the Nadan'khada-Bikin terrane of the Jurassic accretionary wedge revealed late Bajocian and early to middle Bathonian radiolarians in the siliceous-clayey rocks constituting its southern part in the Perepelinaya-Cher� emshanka and Kedrovka areas. Siltstones from the central part of the Bikin segment in the upper reaches of the Vasil'eka River contain radiolarians of the terminal late Tithonian age. Combined with the known dates available for siliceous-clayey rocks from the western part of the Nadan'khada Alin Range and the Ulitka- Zolotoi Klyuch area, these data made it possible to define three stages in the formation of the Bikin segment of the Nadan'khada-Bikin terrane of the accretionary wedge: the terminal Middle Jurassic, the late Titho� nian, and the Berriasian. The formation of this segment lasted approximately 25 Ma.