Correlation between the bedded chert sequence of southwest Japan and δ13C excursion of carbonate sequence, and its significance to the Permian-Triassic mass extinction

Abstract Stratigraphic productivity variations of radiolarians below the Permian-Triassic boundary are examined with Ishiga Diagrams in bedded chert sequences of southwest Japan. The diagrams of two different outcrops, drawn from the thickness variation of chert beds, show common stratigraphic variation, which indicates the diagram is a useful tool for correlation of bedded chert sequence. The common stratigraphic productivity variation is also well correlated to a compiled δ¹³C excursion of shallow carbonate sequences. Bedded chert records a dramatic extinction event in a shallow surface zone of oceans below the Permian-Triassic boundary. The Permian-Triassic mass extinction is divided into three intervals based on the Ishiga Diagrams, the stratigraphic lithological variation of bedded chert sequences, and the δ¹³C curve. The preceding extinction interval in the late Djulfian stage was not as serious an event and the biosphere soon recovered. The event of the main extinction interval commenced in the Dorashamian stage and caused a serious destruction of the biosphere. An event of the aftermath interval during the Early Triassic caused a delay in the recovery from the main extinction interval.