Deposition of "Ryugaishi" limestones in Upper Triassic bedded cherts of Tanba Terrane, Southwest Japan.

Depositional response to the Late Triassic ascent of calcareous plankton in pelagic mid-oceanic plate deposits of Japan

“…Low to middle latitude (Tamura, 1995) Unreported 10°N and 10°S (Ando et al, 2001) Siliceous micrite occurrence Intercalated with ribbon chert Alternating with ribbon chert (Sato et al, 1982;Ohashi, 1984) Alternating with ribbon chert (Igo and Koike, 1975;Kosaka and Ishiga, 1996) (Sato et al, 1982;Nishizono, 19%) Late Carnian to early Norian (Igo and Koike, 1975;Kosaka and Ishiga, 1996) …”

“…Accumulation of thin-shelled bivalves of Middle-Upper Triassic age are known in several places. These include the carbonate platform of Sicily, Italy (Bellanca et al, 1995), Oman (Hauser et al, 2001), South China (Enos et al, 1998), Timor (Martini et al, 2000), and British Columbia (Carlisle and Susuki, 1974;Desrochers and Orchard, 1991), and from the lower Norian deep-water radiolarian chert of the Mino-Tamba-Ashio terrane in central Japan (Kosaka and Ishiga, 1996;Sano and Kojima, 2000). Considering the wide distribution of thin-shelled bivalves from Tethyan platform carbonate to the Panthalassan deep-water radiolarian chert, we infer that they had a planktonic mode of life during their larval or adult stages and accumulated in an openocean realm as the Panthalassa Ocean.…”