夜久野地域舞鶴テレーンの三畳紀石灰岩の岩相と有孔虫化石

抄録

Triassic limestones of the Yakuno Group in the Maizuru Terrane of the Yakuno area consist mostly of ooid grainstone and ooid packstone with many detrital quartz grains. They are closely similar to those of the Hiraki Formation in the Tatsuno-Aioi area in their lithologies, rare occurrence and small size less than 5 m in thickness. These features are also common to those of the shelf limestone blocks of the Kaizawa and Tanoura Formations in the Kurosegawa Terrane. Presence of Meandrospira dinarica, absence of Pilammina densa and much lower taxonomic diversity in the foraminiferal faunas of the Yakuno Group suggest early Anisian (Middle Triassic) age older than those of the Kaizawa and Tanoura Formations.