Radiolarian Biostratigraphy and its International Correlation

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Main results obtained by present co-operative research are summarized as follows :1. Jurassic radiolarian zones in Japan was correlated with those in North America and Europe by means of cross-check using fossil individuals. Although the perfect international radiolarian zonation has not yet been established, these studies clarified the problems in correlation : matching and misma tching among the zones.2. Ages of some Jurassic to Cretaceous radiolarian assemblages were calibrated with newly found ammonite fossils in Shikoku.3. Paleozoic to Mesozoic Radiolaria-bearing siliceous rocks were collected from outside Japan, such as USA, Mexico, New Zealand, Australia, China, USSR, Filippines and Indonesia, and biogeographic, latitudinal and ecological characteristics of the faunas from these specimens were examined. Some of the results are :(1) Middle Triassic to early Jurassic bedded cherts and middle to late Jurassic clastic rocks are the key lithology diagnostic to the late Mesozoic accretionary complex distributed along the eastern continental margin of Asia.(2) In New Zealand, juxtaposition of Tethyan and non-Tethyan faunas was recognized by using radiolarian fossils.4. Oeanic sediments containing well-preserved and not-disturbed radiolarian remains from the Indian and Pacific Oceans were examined. Jurassic to Cenozoic on-land radiolarian zonations were reinforced by these drilling data.5. Phylogenic studies on some genus, such as Jurassic Eucyrtidiellum and Tricolocapsa, made it easy to correlate radiolarian zonations established in Japan with those in other regions, and gave a paleontological basis to the zonations.