北部フォッサ・マグナ地域,別所層からのArgonautinae化石の発見とその地史学的意義

概要

論文の詳細を見る
Fossils of the Argonautinae were discovered from the Middle Miocene Bessho Formation of the central Northern Fossa Magna. The occurrence of the Argonauts from the Middle Miocene has never been reported, though the Upper Miocene examples had long been known from several localities in the San'in and Hokuriku areas both of which are on the Japan Sea coast. Some of the fossils obtained this time were found to be Argonauta tokunagai YOKOYAMA. The discovery of Argonauts in the Bessho Formation and the occurrence of Miogypsina sp. from the Moriya Formation (MATSUMARU et al., 1982) reveal the following interpretations. 1) The Moriya Formation which had been regarded as the oldest sediments in the central Fossa Magna and of the earliest Miocene age and also the Bessho Formation which had been considered to be of the Middle Miocene age are the sediments of an age ranging from the late Early Miocene to the early Middle Miocene. It corresponds to certain horizons from N. 8 to N. 9 of BLOW'S zones by planctonic foraminifera. 2) In the central part of the Fossa Magna area, the seas were connected with each other both from the north and the south iust at the stage of the "Nishikurosawa Transgression."
地学団体研究会の論文
1983-07-25