| Abstract: | The Ryukyu Islands are divided morphologically and geologically into three island groups: north, central and south Ryukyus. North-central Ryukyu represents the geological continuation of the Outer Belt of southwest Japan, composed of Mesozoic-Eocene sedimentary sequences, whereas south Ryukyu is characterized by high-pressure metamorphic rocks, Eocene volcanics and limestone, and lower Miocene sediments. The geological and structural contrasts between north-central and south Ryukyus are conspicuous before the late Miocene transgression covered the whole area. The Ryukyu Islands have been established since then.The successive developments of the Goto-Tunghai-Senkaku basins since the Paleogene, of the Okinawa Trough since the Miocene, and of the grabens near the Island group since the Pliocene, signify a southeastward shift of the basins in relation to the activity in the granite diapir zones accompanied by volcanism. |
