Permalink : http://hdl.handle.net/2115/36766

Radiolarian fossils of early Cretaceous (middle Barremian-early Aptian) were obtained from the country rock (bedded red chert) of the manganese deposit of the Hinode mine in the Tokoro Belt. By this discovery of radiolarians the geological age of the formation of the manganese deposit of the Hinode mine was determined for the first time to be formed during a short period of ca. 110-120 Ma. Radiolarian fossils of early Cretaceous in age were also extracted from bedded cherts of the Wakasa, Koryu, Syotosibetu, and Hokkaido mines which were similar manganese deposits to the Hinode mine. This fact suggests that manganese deposits in the Tokoro Belt were formed almost simultaneously during late early Cretaceous time.