Stratigraphy and fossils of the Pliocene Ikego Formation of Urago-cho, Yokosuka City, north-eastern part of the Miura Peninsula, south-central Japan
Kanie, Y.; Kuramochi, T.; Shibata, K.; Ebiko, T.
Yokosuka-shi Hakubutsukan kenkyu hokoku. Shizen kagaku 55
Stratigraphic reconsideration of Urago-cho, Yokosuka City revealed that the uppermost part of the Pliocene Ikego Formation is exposed in this area. The area is located on the north-eastern part of the Miura Peninsula, south-central Japan. The location has been assigned to the Urago and Nojima Formations, the basal part of the Plio-Pleistocene Kazusa Group. However, lithofacies of the study area consists of solid tuff and tuffaceous siltstone including scoria breccia, and is different from that of Natsuhima and Nojima, which is composed of easily eroded tuffaceous sandstone. In addition, a new fossil assemblage was found from the Ikego Formation of the study area. This fossil assemblage includes: bivalves, gastropods such as Neptunea sp., scaphopods, brachiopods, and cirripedians. It lacks, however, Calyptogena sp. which dominated in the formerly reported fossil assemblage from the Ikego Formation of the Ikego area in Zushi City. On the basis of taphonomic features, the fossil bearing rocks are interpreted to have been deposited at upper bathyal zone of approximately more than 100 m in depth.