名古屋市東部,鳴子丘陵の瀬戸層群矢田川累層

抄録

The Pliocene Yadagawa Formation in the Naruko Hill, east of Nagoya, is composed of fluviatile-lacustrine loose sediments. It is lithologically divided into three members, namely, the Nisshin, Takahari and Idaka Members in asending order. The total thickness attains to 110 m. The Nisshin Member, more than 10 m in thickness, are composed of alternation of sand and mud beds. The Takahari Member, 50 m in thickness, is composed of alternation of gravel, sand, silt, and clay beds. The Idaka Member, more than 50 m in thickness, is characterized by gravelly beds with intercalation of sand, silt and clay beds. The Yadagawa Formation shows a homoclinal structure with N-S strike and gentle dip to the west. Five volcanic ash layers are intercalated in the Yadagawa Formation. They are named the Togo, Nagakute, Kumanomae, Takinomizu I, Takinomizu II volcanic ash layers in ascending order. On the basis of the tephrostratigraphy, the Yadagawa Formation in the Naruko Hill is correlated to the middle and upper parts of the Yadagawa Formation in the Owari Hills. The following plant fossils occur in the lower part of the Idaka Member: Fagus palaeocrenata Okutsu, Quercus serrata -Thunb,, Quercus variabilis Blume, Styrax rugosa Miki, etc.