Radiolarian Biostratigraphy at the Triassic / Jurassic Period Boundary in Bedded Cherts from the Inuyama AreaCentral Japan

Abstract

Vertical distributions of microfossils such as radiolarians and conodonts across the Triassic/Jurassic (T/J) boundary were clarified through the biostratigraphic study of two continuous sequences of bedded cherts in the Inuyama area, central Japan. Three types of taxons were recognized around the T/J boundary, 1) Upper Triassic type such as Squinabolella, 2) Upper TriassicLower Jurassic type such as Canoptum, and 3) Transition type (possibly earliest Jurassic type) such as Parahsuum and Bipedis....