付加体深海堆積相における中?古生代微化石研究の最近の進展:放散虫およびコノドン卜研究の現状と将来の展望

摘要

The study of accretionary tectonics in Japan is intrinsically linked to Paleozoic and Mesozoic microfossil research, with advances in one area determining progress in the other. This paper provides a review of biostratigraphic and biological research of radiolarians and conodonts conducted in Japan over the past 25 years. Following 'the Ra- diolarian Revolution' that was a breakthrough of interpretation of accretionary complexes by establishment of radiolarian biostratigra- phy in the late 1970s and early 1980s, our understanding of radiolarian biostratigraphy has advanced significantly. Notably, since the 1990s the resolution of radiolarian biozones has greatly increased, leading to an improved understanding of middle Paleozoic to Mesozoic biostratigraphy. In contrast, the study of conodont biostratigraphy in Japan has been limited over the last 25 years. However, conodonts are increasingly acknowledged internationally as an important index fossil group for the study of Permian and Triassic stratigraphy. Further advances in radiolarian and conodont biostratigraphy will be gained from more accurately calibrating microfossil biozones to one other and to a chronostratigraphic scale. The study of radiolarian biology in Japan has focused on phylogenic analysis and reproduction. Well-preserved Triassic conodont specimens have been identified within pelagic sedimentary rocks in accretionary complexes, facilitating studies of conodont paleontology. The future of radiolarian and conodont research depends on the next generation of researchers. For the further progress of the microfossil study, more effort should be placed on student training and popularizing microfossils.