吐喝喇列島・小宝島の完新世隆起サンゴ礁段丘地形と堆積構造 [in Japanese] Morphology and Anatomy of Holocene Raised Coral Reef Terraces in Kodakara Island, Tokara Islands, northwestern Pacific, Japan [in Japanese]
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Well-developed Holocene raised coral reef terraces are formed in Kodakara Island (29°13'N 129°19'E), TokaraIslands, northwestern Pacific, Japan. Detailed morphology and sedimentary structure of the raised reef terraces areobserved by field survey through the terraces surface and core drillings. The Holocene raised reef in KodakaraIsland are divided into three terraces (TI to III). The surface geo-biological facies and paleo-morphology such asspur and groove system or reef mounds are well preserved on these terraces. The raised coral reefs in KodakaraIsland consist of reef flats and reef slopes. No lagoon formed in these terraces. On the raised reef surface, weobserved five distinct reefal facies (S-f1-5). The platy and encrusting Acropora facies is the major constituent ofthe terrace surfaces. We obtained seven drilling cores (B1 to 7) from Terraces I and II along a transect in thesouthern part of the island. The thickness of the Holocene reef is more than 14m which is approximatelyequivalent to the Holocene reefs in the middle and southern Ryukyu Islands. Sedimentary structure consists ofseven facies (C-f1-7: five reefal and two non-reefal facies). The drilling cores indicating the shallowing sequence at the upward of the cores which characterized by platy-encrusting Acropora facies overlying massive Porites,favid and/or encrusting-foliaceous coral facies. It may indicate the environmental change such as wave-energygradients and turbidity during the reef development.
- Okayama University Earth Science Report
Okayama University Earth Science Report 15(1), 33-65, 2009-03-31