A revised Jurassic radiolarian zonation for the South Belt of the Chichibu terrane, western Kyushu, southwestern Japan

Permian, Triassic and Jurassic sedimentary and volcaniclastic rocks are distributed in the South Belt of the Chichibu terrane. Unfortunately, they are not part of a sequence but are disordered masses of mappable units. Several sequences of Jurassic age are found in the Kuma massif on western Kyushu, the western part of the Belt. The radiolarian succession containing the sequences encompasses nearly the entire Jurassic Epoch. Detailed radiolarian successions from seven sections are discussed; six sections consist mainly of bedded cherts and siliceous shales with minor terrigenous black shales. One section consists of terrigenous black shales with oolitic limestone. The radiolarian zonation presented here has been defined by the first and last appearances of age-diagnostic species from stratigraphically coherent intervals. Thirteen radiolarian datum levels have been established defining ten zones and six subzones representing the Lower to Upper Jurassic. These zones are correlated with zones previously established by several workers for coeval strata of the world (western Tethys, Caucasus, Pacific coast of Russia, Japan, western Pacific Ocean and North America).