Submarine geology off west coast of Kyusyu.

Abstract

The Hydrographic Department of Japan carried out the investigation of submarine topography and submarine geology off the west coast of Kyusyu in 1973 and 1974. The stratigraphy of the seabed was classified into E layer (acoustic basement) to A layer (surface layer) by means of a seismic profiler of air gun system. The age of each layer was confirmed as under-mentioned which was collated with the paper of Mizuno, et al (1971), and Kimura, et al (1975). A } Quaternary B C Pliocene D }Miocene and Pre-Miocene E Tectonic movements and the general structure were also confirmed as in the following: 1. After the sedimentation of E Layer, up rifting tectonic movement occurred, and then fault of NNE-SSW direction along the west side of Tusima was formed. In succession, up-rift movement occurred adjacent to Goto Retto-Danjo Gunto and Goto Banks. Related to this movement, a dam was formed in front of Tonghai Shelf, and a sedimentary basin took shape by the NNE-SSW fault on the eastern edge of the No. 1 Goto Bank. 2. According to these tectonic movements, Tusima Goto Tectonic Line and the original topography of the north end of Okinawa Trough were constructed. After the sedimentation of C layer, Okinawa Trough performed down warping along NE-SW axis in front of the marginal area of Tunghai Shelf.