Biostratigraphic and lithostratigraphic studies of strata near the Permian–Triassic (P–T) boundary, especially in carbonate and terrigenous facies, have been conducted for the Tethys, peri-Gondwana, and Boreal regions. Recently, environmental conditions near the P–T boundary, including those that caused the mass extinction, have received special attention through biostratigraphic, geochemical, and sedimentologic approaches (e.g., Sweet et al., 1992; Erwin, 1993).
Permian and Triassic marine successions are known to have been widely deposited, not only in near-shore situations but also in open-marine, pelagic environments (e.g., Ishiga and Imoto, 1980; Yao, Matsuda, and Isozaki, 1980). The P–T boundary is found in a sequence of pelagic sediments now incorporated into the Jurassic accretionary complexes in southwest Japan (e.g., Yamakita, 1987; Ishida, Yomashita, and Ishiga, 1992).
The bedded chert in the Mino-Tamba Terrane was deposited in a pelagic environment, with little continental influence, and the strata range from Upper Carboniferous to Middle Jurassic (Imoto, 1984a). Near the P–T boundary, the section is characterized by intergradings of bedded chert, siliceous claystone, black mudstone, and dolostone. Coarse-grained terrigenous components transported by currents are not included in those rocks. That pelagic sequence records secular and widespread oceanic changes in the Panthalassan Ocean near the P–T boundary.
In this chapter we attempt to clarify the Upper Permian–Lower Triassic successions in the Mino-Tamba Terrane. The palaeoceanographic implications of the pelagic sediments are considered in terms of P–T depositional and habitual fluctuations in the Panthalassan Ocean.