Chemical Sedimentology of Pelagic Clay Minerals Contained in Pelagic Deep-Sea Cherts

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Geochemical analyses on 172 cherts and associated sedimentary rocks from the Okinawa Islands and Hokkaido reveal some geochemical characteristics for pelagic and hemipelagic cherts. Excluding some local basal cherts above the hyaloclastite, pelagic cherts are characterized by a continuous linear plots with high correlation between Fe and Mg. As well, the correlation between Fe and K is high for pelagic cherts. On the other hand, the hemipelagic cherts are characterized by poor correlations among Fe, Mg, and K.Jurassic to Cretaceous pelagic cherts, both as bedded red cherts in the abyssal floor below the CCD and as nodular flints on the pelagic seamount above the CCD, are exposed in the Ie Island and Hokkaido. The pelagic bedded red cherts occur as monotonous and continuous red cherts in the stratigraphic succession. The stratigrap of these pelagic cherts on the land is well correlated with the stratigraphy of pelagic cherts, both as cherts below the CCD and as above the CCD, in modern deep-se floors.