Study on evolution of Carboniferous-Permian-Triassic reef-building organisms and paleoenvironment of Panthalassan Ocean

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Special interest of this research project is in the significant rock-forming role of calci-microbes mainly of cyanobacteria and sessile foraminifers, both of which are usually small-sized and inconspicuous in the field and under the microscope. Microbialites and related organosedimentary structures were described as well as the paleontological characters and stratigraphic distribution of the calci-microbes. Chosen for study are Carboniferous-Permian Akiyoshi and Omi Limestones, Permian Funabuseyama Limestone, Triassic Konose Limestone, and a few other limestone-units. All the examined limestone units were formed as oceanic sediments of seamount top-capping buildups in an open-ocean setting of the Panthalassan Ocean. Rocks are at present exposed as large-sized isolated masses within Permian and Jurassic accretionary complexes of southwest Japan. More than 300 pieces of thin-sections, including extra-sized ones, were prepared from rock-samples, most of which are biostratigraphically cont … More rolledThe careful microscopic examination leads the author to a conclusion that calci-microbes greatly contributed to the Carboniferous, Permian, and Triassic shallow-marine carbonate sedimentation at the top of Panthalassan seamounts. Through this research project, diverse types of microbialites and related organosedimentary structures were recognized in all the examined limestone units. As well, several problematic microbes of uncertain taxonomic affinity were found out in several limestone units. The sedimentological properties of the microbialites and related structures and paleontological characters of calci-microbes were in separate described.Among many important results of the project, to be stressed is the occurrence of diverse microbialites in Lower-Middle Carboniferous and Upper Triassic rocks. This was unexpected, for the rocks of these ages are know to be characterized by the predominance of reef limestones formed by large-sized metazoans. This finding implies that calci-microbes acted as stratigraphically widespread and significant rock-forming biotas. Less