Depositional response to the Late Triassic ascent of calcareous plankton in pelagic mid-oceanic plate deposits of Japan

Calcareous nannofossils occur in Upper Carnian to Middle Norian siliceous micrites of the Sambosan accretionary complex, the origin of which is the Panthalassan Ocean. The siliceous micrite consists of presumably calcareous nannofossil derived lime–mud and locally yields abundant radiolarians and filaments (thin-shelled bivalves). This type of accumulation of siliceous micrite represents a significant change in oceanic sedimentation since Late Triassic times, which appears as a depositional response to the simultaneous Late Triassic rise of calcareous nannoplankton in the world-ocean.