On the Pliensbachian/Toarcian boundary in the Lower Jurassic Toyora Group in southwest Japan

• Autorzy: Nakada K. , Matsuoka A.
• Języki publikacji: EN

Abstrakty

EN

The Toyora Group, consisting of continental shelf sediments, is exposed in southwest Japan. It is divided into three formations, the Higashinagano, the Nishinakayama, and the Utano formations in ascending order. The Nm Member, the lower part of the Nishinakayama Formation, has yielded abundant ammonites, indicating successive ages of Early Toarcian. The ammonite zonation was established on these materials, but the Pliensbachian/Toarcian (P/T) boundary was not defined clearly in previous studies. A total of 99 ammonite specimens including 11 genera and 16 species were collected along the Sakuraguchi-dani Valley. The first occurrence of Dactylioceras helianthoides is the most suitable candidate for drawing the P/T boundary in the Toyora Group, the boundary being drawn at least 35.5 m lower than the previously indicated.

Słowa kluczowe

EN

Jurassic; Pliensbachian-Toarcian boundary; Toyora Group; southwest Japan; ammonites

• Wydawca: Państwowy Instytut Geologiczny - Państwowy Instytut Badawczy
• Czasopismo: Volumina Jurassica
• Rocznik: 2009
• Tom: Vol. 7, no. 1
• Strony: 47--54
• Opis fizyczny: Bibliogr. 23 poz.

Twórcy

autor

Nakada K.

autor

Matsuoka A.

• Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan,

Bibliografia

• 1. Arkell W. J. 1956. Jurassic geology of the World. Oliver and Boyd Ltd: 806p.
• 2. Dean W. T., Donovan D. T. and Howarth M. K. 1961. The Liassic ammonite zones and subzones of the North-West Europe Province. Bulletin of the British Museum (Natural History), Geology, 4: 435-505.
• 3. Elmi S., Rulleau L., Gabilly J. and Mouterde R. 1997. Toarcien. In: E. Cariou, P. Hantzpergue (Coord.), Groupe Fran~ais d'Etude du Jurassique. Biostratigraphie du Jurassique ouesteuropeen et mediterraneen: zonations parall les et distribution des invertebres et microfossiles. Bulletin du Centre de Recherches. Elf Exploration Production Mémoires, 17: 120-125.
• 4. Gabilly J. 1976. Le Toarcien Thouars et dans le Centre-Ouest de la France, evolution de la fauna? Harpoceratinae, Hildoceratinae. Éditions du Centre National de la Recherches Scientifiques. Les Stratotypes fran~ais, 3: 1-217.
• 5. Guex J. 1973. Apercu biostratigraphique des ammonites du Toarcien inferieur du Moyen-Atlas morocain et discussion sur la zonation de ces sous-etages dans les series mediterraneennes. Eclogae Geologicae Helvetiae, 66: 493-523.
• 6. Hayami I. 1959. Lower Liassic lamellibranch fauna of the Higashinagano Formation in West Japan. Journal of Faculty of Science, University of Tokyo, Section 2, 12: 31-84.
• 7. Hirano H. 1971. Biostratigraphic study of the Jurassic Toyora Group, Part 1. Memoirs of Faculty of Science, Kyushu University, Series D, 21, 1: 93-128.
• 8. Hirano H. 1973a. Biostratigraphic study of the Jurassic Toyora Group, Part 2. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, 89: 1-14.
• 9. Hirano H. 1973b. Biostratigraphic study of the Jurassic Toyora Group, Pt. 3. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, 90: 45-71.
• 10. Howarth M. K. 1973. The stratigraphy and ammonite fauna of the Upper Liassic Grey Shales of the Yorkshire Coast. Bulletin of the British Museum (Natural History), Geology,24, 4: 235-277.
• 11. Jenkyns H. C. 1988. The Early Toarcian (Jurassic) Anoxic Event: stratigraphic, sedimentary, and geochemical evidence. American Journal of Science, 288: 101-151.
• 12. Kobayashi T. 1926. Note on the Mesozoic Formation in Province Nagato, Chugoku, Japan. Journal of the Geological Society of Japan, 33: 1-9.
• 13. Matsumoto T. and Ono A. 1947. A biostratigraphic study of the Jurassic Toyora Group, with special reference to ammonites. Science Reports of the Faculty of Science, Kyushu University, Geology, 2, 1: 20-31.
• 14. Oppel A. 1856-1858. Die Juraformations Englands, Frankreichs und des sudwestlichen Deutschlands. 1-438 (1856); 439-586 (1857); 587-857 (1858).
• 15. Sato T. 1956. Correlation du Jurassique inferieur japonais en basant sur les ammonites fossiles. The Journal of the Geological Society of Japan, 62, 732: 490-503.
• 16. Sato T. 1960. A propos des courants oceaniques froids prouves par l'existence des ammonites d'origine arctique dans le Jurassique japonais. International Geological Congress Report of the 21st Session Norden, 12: 165-169.
• 17. Sato T. 1962. Etudes biostratigraphiques des ammonites du Jurassique du Japon. Mémoires de la Société Géologique de France, 94: 1-122.
• 18. Schlatter R. 1982. Zur Grenze Pliensbachian-Toarcian im Klettgau (Kanton Schaffhausen, Schweiz). Eclogae Geologicae Helvetiae, 75:759-771.
• 19. Schlatter R. 1985. Eine bemerkenswerte Ammoniten- fauna aus dem Grenzbereich Pliensbachium/ Toarcium der Baar (Baden/ Wurttemberg). Stuttgarter Beiträge zur Naturkunde, B, 112: 27p.
• 20. Tanabe K. 1991. Early Jurassic macrofauna of the oxygen-depleted epicontinental marine basin in the Toyora Area, West Japan. Proceedings of Shallow Tethys, 3: 147-157.
• 21. Yabe H. and Eguchi M. 1933. Anabachia cyclolitoides sp. nov. from Japan with remarks of the genus Anabachia. Japanese Journal of Geology and Geography, 10, 3-4: 119-124.
• 22. Yokoyama M. 1904. Jurassic ammonites from Echizen and Nagato. Journal of the College of Science, Imperial University of Tokyo, 19: 1-17.
• 23. Wiedenmayer F. 1980. Die Ammoniten der Mediterranen Provinz im Pliensbachian und unteren Toarcian auf grund neuer Untersuchungen im Generoso-Becken (Lombardische Alpen). Denkschriften der Schweizerischen Naturforschenden Gesellschaft, 93: 1-260.