Integrated Upper Triassic Conodont and Radiolarian Biostratigraphies of the Panthalassa Ocean

Abstract

The Late Triassic conodont biostratigraphy of two pelagic chert sections (sections N and Q) in the Inuyama area, central Japan, was investigated to calibrate the Triassic radiolarian zonation proposed by Sugiyama in 1997 with the conodont zones and the standard Triassic timescale. Based on the stratigraphic distributions of marker species, six conodont zones were defined: the Paragondolella? tadpole interval Zone, the Quadralella tuvalica interval Zone, the Epigondolella quadrata interval Zone, the E. triangularis interval Zone, the Mockina postera interval Zone, and the M. bidentata Zone. These conodont zones are comparable to the standard Carnian and Norian conodont zones of North America and the Tethys. The Carnian-Norian boundary in the sections studied is tentatively placed between the last occurrence of a Carnian species (Q. tuvalica) and the first occurrences of Norian species (E. quadrata and E. spatulata). The intercalibrated conodont—radiolarian biostratigraphy from the sections we studied accurately calibrates the radiolarian zones in Japan with standard chronostratigraphic stages and substages.