Causation of barrier reefs of the Sekisei Lagoon and fringing reefs of the southern Okinawa Island in the southern Ryukyu Islands on island shelf on the basis of drilling and shallow reflection investigation

冲绳岛南部古石滩海岸的全新世珊瑚礁在距今7600年左右开始在15 ~ 20 m深的平面上向上生长。古什干第一期珊瑚礁形成于约6000年前，是由于地区隆起所致。第二次是在距今4000年前的海上形成的，第二次是在距今2500年前的海上形成的。关成礁湖全新世珊瑚礁在20 ~ 25 m深的平面上开始向上生长。石垣岛南部约7000 ~ 6000年左右，由于隆升运动，形成了第一期珊瑚礁。约5500 ~ 5000年BP，竹美岛发育边缘礁，关成礁湖内部形成斑礁。大约在距今3600年左右，关成礁湖外围形成了堡礁。由于隆升运动和海平面变化，该地区形成了全新世三期珊瑚礁。

Holocene coral reef in Gushichan coast in the southern Okinawa Island commenced to grow upward on the flat surface about 15〜20 m deep about 7600 yrs BP. The first phase of coral reef in Gushichan formed about 6000 yrs BP due to uplifted area. The second one was developed offshore about 4000 yrs BP, then after about 2500 yrs BP the third one was formed offshore. Holocene coral reef in the Sekisei Lagoon started to grow upward on the flat surface about 20〜25 m deep. In the southern Ishigaki Island, the first phase of coral reef was formed about 7000〜6000 yrs BP due to uplift movement. About 5500〜5000 yrs BP, a fringing reef developed in Taketomi Island and patch reef was formed in the inner part of the Sekisei Lagoon. Then about 3600 yrs BP, barrier reef was formed in the outer part of the Sekisei Lagoon. Three phases of Holocene coral reef have been formed in these areas due to uplift movement and sea-level change.