大阪湾の"沖積層"とその基底(大阪湾の"沖積層"-2-)

概要

論文の詳細を見る
The sonic survey by "SPARKER" revealed the following facts concerning the relations between the submarine topography and the youngest deposits in Osaka Bay.1) The unconsolidated deposits of Osaka Bay are divisible into A and B layers (Fig. 2). B is infered to be the latest Pleistocene sediments deposited in the stage when the sea level retarded at 20m below the present level about 10, 000 years ago. This stage may be identified with the Alleröd oscillation. A is the Holocene sediments formed by the quick transgression occurred in the next stage.2) Submarine flat planes are classified as follows.a) -10m; wave-cut terrace formed at the present sea level.b) -10∼-20m; depositional surface of A.c) -40∼-50m; approximate depositional surface of B.Generalized profile of Osaka Bay shown in Fig. 5 indicates the relations between the change of sea level and the deposition of A and B.3) The surface of the base of the unconsolidated sediments is contoured in Fig. 3, on which a system of buried river channels can be recognized. It is named Paleo-Osaka River, which may have been entrenched in the regression stage of maximum phase of Würm Ice Age. The dotted lines in Fig. 3 express the subsiding movement of Osaka Bay since that age.4) Akashi and Kitan straits have their origin in the Paleo-Osaka River system, but their sea caldrons reaching more than -100m have been formed by the submarine erosion after the deposition of B.
日本第四紀学会の論文