11:15 AM - 11:30 AM
[MIS20-03] Integrated biostratigraphy and magnetostratigraphy of the Upper Triassic to Lower Jurassic bedded chert sequences from Inuyama area, central Japan
Keywords:Late Triassic, magnetostratigraphy, biostratigraphy, bedded chert, Mino belt, Panthalassa
Based on recent conodont taxonomy and the stratigraphic distribution of marker species, eight conodont zones were defined: Paragondolella? tadpole interval Zone, Quadralella tuvalica interval Zone, Epigondolella quadrata interval Zone, E. triangularis interval Zone, Mockina postera interval Zone, Mockina bidentata interval Zone, Misikella hernsteini interval Zone, and Misikella posthernsteini interval Zone. These were correlated with the coeval radiolarian zonation established by Sugiyama in 1997, and comparable to that in British Columbia, the Pizzo Mondello section, the Steinbergkogel section, and other sections in southwest Japan.
Magnetostratigraphic results delineate 20 substantive normal and reverse magnetozones, defined by measurement of 357 samples. Although the magnetostratigraphic data in the vicinity of the early-late Carnian boundary is the first record from the marine section, the magnetostratigraphy of samples in Carnian-Rhaetian interval was well correlatable with that of Tethyan marine sections. This correlation implies that the bedded chert of Inuyama area was deposited in the Northern Hemisphere, assuming that the rocks in the Tethyan marine sections were deposited in the Northern Hemisphere. The correlation of the magnetostratigraphic data also suggests that loss of the stratigraphic record at the Triassic-Jurassic boundary (TJB) in the study sections, possibly due to structural erosion or hiatus. The intercalibrated conodont–radiolarian biostratigraphy and magnetostratigraphy from the studied sections accurately calibrates the radiolarian zones in Japan with standard chronostratigraphic stages and substages.