Journal of the Faculty of Science, Hokkaido University. Series 4, Geology and mineralogy;Vol.XXII, No.3


Jurassic and Cretaceous Radiolarians from the pre-Tertiary System in the Hidaka Belt, Maruseppu Region, Northeast Hokkaido

Iwata, Keiji;Tajika, Jun

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We have made a study of the pre-Tertiary Hidaka Supergroup (the Kanayama Formation), which is distributed at the most easterly portion of the Hidaka Belt, in order to ascertain the age of accumulation of this supergroup. The Kanayama Formation consists mainly of broken formations in which clastic rocks of terrigenous origin predominate and many exotic blocks are included in the scaly shale matrix. The tuffaceous shale of this format ion yielded Amphipyndax tylotus―Clathrocyclas diceros radiolarian assemblage which indicates late Campanian to early Maastrichtian age. And a late Jurassic Stylocapsa (?) spiralis and early Cretaceous Sethocapsa trachyostraca―Staurosphaera sepremporatus assemblages were obtained from chert block within the melange facies of the Kanayama Formation. This formation may represent a part of accretionary complex formed by subduction process during the late Cretaceous.