A study of geomorphological formation in coastal region for the northern migration of coral reef development with global warming

在全球变暖的时代，珊瑚礁地层预计将发生北方迁移。西北太平洋是罕见的礁体大小和分布向纬度极限逐渐减小的地区。本文讨论了不同纬度四个礁区的生物礁发育情况（种子岛-马吉岛地区、土加罗群岛、冲绳、小笠原群岛）。琉球北方北纬30度附近的礁发育（种子岛-马吉岛地区）的特征如下：1）启动增长滞后于海平面上升，2）由于主要的珊瑚礁发展停止不到2,000年，珊瑚礁发展持续时间短，（3）缓慢向上生长速率在1 ~ 2 m/ka之间。高纬度生物礁生长的特点是礁形成的地点特异性和礁发育的时间范围窄。高纬度小型生物礁可能在较短的地质时期内形成。小笠原群岛的礁体地形、内部结构和发育与北方琉球相比具有独特性。有必要对小笠原群岛的珊瑚礁进行进一步调查。

The northern migration of the coral reef formation is expected in the era of global warming. The northwestern Pacific is rare place where the reef-size and reef-distribution decrease gradually to the latitudinal limit. This study discusses the reef development in four reef area of different latitudes (Tanegashima-Magejima area, Tokara Islands, Okinawa Island, Ogasawara Islands) by drillings.The reef development in the northern Ryukyus around the latitude of 30 degree N (Tanegashima-Magejima area) characterized by follows: 1) lagged start-up growth behind the sea level rise, 2) short duration of reef development as the major reef development ceases less than 2,000 years, 3) slow upward growth rate between 1 to 2 m/ka. The site-specific reef formation and the narrow time range of reef development may characterize the high-latitude reef growth. The small high-latitude reef may build in the short geological time period. However, the timing and locality of reef development is hard to expect.In Ogasawara Islands, reef topography, internal structure and development are unique comparing with the northern Ryukyus. The further investigation is necessary for coral reefs in Ogasawara Islands.