Abstract
This paper describes petrographic properties and radiolarian ages of clastic rocks interbedded with Triassic bedded chert in the Ozaki-Amaike and Hisuikyo areas of the southern Mino terrane, central Japan.The clastic rocks in the Ozaki-Amaike area are 2.5 to 7 cm thick, and consist of angular, silt- to granule-sized clasts of chert, siliceous shale, basic or intermediate volcanic rocks, volcanic glass, polycrystalline quartz and radiolarians. Rarely found clasts include dolomite-bearing rocks, plagioclase, apatite and lutecite. Clastic rocks in the Hisuikyo area are contained in chert beds as laminae and scattered particles. Fourteen chert formations with the clastic materials occur in 4 fault-bounded zones, and apparently 25 clastic rocks-bearing chert beds can be observed in this area. Clast composition of the rocks is similar to that of the Ozaki-Amaike area, but they characteristically include glauconite-like minerals with or without siderite. Permian and Triassic conodonts are concentrated in the clastic rocks.Radiolarian fossils extracted from chert beds which occur above and below the clastic rocks indicate that the ages of clastic beds are early Carnian in Ozaki, middle Ladinian and early Carnian in Amaike, and late Anisian to early Ladinian in Hisuikyo ; although the ages are concentrated in the interval between late Anisian to early Carnian, they are not on the same horizon.Possible provenance of the clasts are oceanic island, island arc, continental shelf, and older accretionary complex.
