抄録
The Udo Hills consist of the Pleistocene clastic deposits, which are, from the bese upwards, Negoya, Kunozan, Kusanagi, Oshika, Kuniyoshida Formations. In this study, the Kusanagi and Kunozan Formations are discussed on the basis of their facies. The Kusanagi Formation characterized by shallow muddy deposits which are divided into five members, the I, II, III, IV and V. The I and II Members contain mud bed, alternating beds of sand and mud and sand in ascending order. The overlying III and IV Members consist of mud bed and alternating beds of sand and mud, with intercalated gravel beds in the north-western of the area. The uppermost member(V) where it is found in the southwest of the area comprises sand and gravel beds. The Kusanagi Formation unconformably overlies the Kunozan Formation. The Kusanagi Formation was deposited in an embayment open to the northeast, which was formed on the elevated Kunozan Formation. Divided by two peninsulas, this embayment is separated into three areas which are the east of Oshika, Hirasawa to Kusanagi and Mabase to Utozaka. The Kusanagi Formation was formed by four transgressions. The transgression of the IV Member is thought to be more rapid than the transgressions of the other members judging from its facies and fossils. With reference to the result of pumice analysis, Member IV may be correlated to the Shimosueyoshi transgression in the Kanto region.
