熊本県天草下島の姫浦層群上部亜層群の地質の再検討

概要

論文の詳細を見る
The Upper Himenoura Subgroup is distributed in Amakusa-Shimojima Island, Kyushu, Japan. The subgroup is divided into four formations, namely, Units I, II, III and IV in ascending order. These formations are further divided into a, b and c members, respectively. These formations have been assigned to the Middle Campanian, Upper Campanian, Uppermost Campanian or Maastrichtian, Maastrichtian-Paleocene by megafossils. Recently, we found fossil molluscs and Nummulites from the subgroup at some localities and also carried out fission-track age determinations on three pyroclastic rock samples of the group. We re-examined these megafossils and revised the geological map (Tashiro and Otsuka, 1978) of this area. Ages obtained by a grain-by-grain method and an external detector method, using zircon crystals separated from the samples, are shown in Table 1.
日本古生物学会の論文
1985-06-11