美濃帯味噌川コンプレックスのチャートおよび珪質泥岩から産出したジュラ紀中世および新世の放散虫化石群集

概要

論文の詳細を見る
The Misogawa Complex is a Late Jurassic accretionary complex widely exposed in the eastern part of the Mino Terrane, central Japan. The complex is mainly composed of sandstone, mudstone and chert, and they are generally deformed in various degrees. Among the complex, exceptionally well-continuous sequences are exposed along the Nakazawa-gawa River in the Kisofukushima area, Nagano Prefecture. Pelagic chert is conformably covered by hemipelagic siliceous mudstone in the outcrop. Middle to Late Jurassic radiolarian assemblages corresponding to Tricolocapsa plicarum, T. conexa and Stylocapsa(?) spiralis zones (Matsuoka, 1995) were found in the sequence. The radiolarian biohorizon of the top of the chert is correlative with Stylocapsa(?) spiralis zone that ranges from latest Middle to early Late Jurassic. The age of the stratigraphic boundary is interpreted as the arrival time of the oceanic plate at the outer trench where the terrigenous materials were first deposited in the sequence. The age indicated by the radiolarians from the Nakazawa-gawa River sequence is the youngest evidence in the eastern Mino Terrane.
信州大学の論文