Microfossil Assemblages from the Late Jurassic to Early Cretaceous Nikoro Pelagic Sediments, Tokoro Belt, Hokkaido, Japan

Abstract

The Tokoro 13elt in Hokkaido collstitutes one of the major ophiolitic belts in the Japanese Islands In order to clarify the origin of the Tokoro ophiolitic rocks which are represented by the Nikoro Group new micropaleoIItologic data of the Nikoro pelagic sedimellts are presellted in this paper as regards radio-1arians caleareous nannofossils and foraminifers The results show tllat(1)the age of the Nikoro Group ranges from the Kimmeridgian to the early Albian and(2)the Nikoro pelagic rocks were deposited in a seamount environment near an oceanic ridge in the paleoequatorial productive region where the paleodepth was about 1000 m and above the CCD