長野県諏訪湖北方の新第三系横河川累層の中新世放散虫化石

概要

論文の詳細を見る
The Miocene stratigraphy along the Yokokawa River was revised. The strata formerly included to one formation were divided into the Yokokawagawa and Hachibuseyama Formations in ascending order. The two formations are in fault contact, and their geologic structures are discordant each other. The Yokokawagawa Formation was subdivided into four members, namely, Nakanosawa Sandstone Member, Tanakoba Black Mudstone Member, Yokokawagawa Conglomerate Member and Hikawasawa Greenstones Member in ascending order. Radiolarian fossils such as Cyrtocapsella tetrapera, C. cornuta, Stichocorys wolffii, S. armata and Melittosphaera magnaporulosa, occurred from the Tanakoba Black Mudstone Member of the Yokokawagawa Formation. These radiolarians can be correlated with the Melittosphaera magnaporulosa Zone proposed by Nakaseko and Sugano (1973), or Calocycletta costata Zone by Funayama (1988) and Riedel and Sanfilippo (1978). Then, the Yokokawagawa Formation can be assigned to late Early Miocene to early Middle Miocene (N7 to N8) in age.
信州大学理学部の論文
1990-10-30