明石層群・播磨層群について

抄録

The loose sedimentary strata constructing the Meimi Hills are divisible into two, one the Akashi Group (Pliocene ?) and the other the Harima Group (Pleistocene) . The Akashi Group overlies unconformably on the basement rocks including the Kobe Group (Miocene) , Liparite, Quartz-Diorite and Paleozoic strata, and is made up of fluvial gravels and sands, greenish lacustrine clays and bluish marine clays. The thickness of the Akashi Group is over 150m. It is well known that the greenish lacustrine clay beds contain Stegodon akashiensis, Metasequoia japonica and Juglans megacinerea etc. The Harima Group rests on the Akashi Group with a remarkable unconformity, the thickness of which is 0〜10 m +. Along the Akashi Coast, the Harima Group consists of the following deposits filling the ancient valleys : basal gravels with sands, marine clays (with Elephas namadicus naumanni), sands or silts and gravels with reddish matrix, in ascending order. This succession indicates one sedimentary cycle. In the Meimi Hills, the Harima Group consists of gravels with reddish clayey matrix, and forms the Meimi terrace plain. This gravels bed is deltaic and fulvial plain deposits. The authors consider that the unconformity between the Akashi Group and the Harima Group, probably indicates the Riss Glacial Stage and the Harima Group Riss-Wurm Interglacial Stage.