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作者Gong, Shou-Yeh;Wang, Y. H.;Wu, C.C.;Shen, C.C.
出版日期2016
著作名稱Origin and Development of the Dongsha Island, South China Sea in the Holocene
會議論文集Conference Abstract
頁數28145
會議名稱13th ICRS
會議地點Honolulu
會議日期2016/7
主辦單位ISRS
國際性會議Y
主題地質
關鍵字Dongsha Island; Sand Cays; atoll islands; Holocene,;South China Sea
摘要The Dongsha Island is the only island of Dongsha Atoll that is located on the Dongsha Rise offshore Canton. The atoll stands about 300-400 meters above the surrounding sea floor with a diameter of about 24 km, and the island measures 2.8 km in length (East-West) and 0.86 km in width. Our understanding about reef geology of the Atoll is very limited due to its remote locality. To explore the Holocene geo-history of Dongsha island, this study drilled 3 cores on the Island with depths of 20-23.3 m and 1 on the reef flat west to the island with depths of 21.2 m. Lithological sequence of each core was established, a total of 16 fossil corals were dated by AMS 14C or 230Th methods and an East-West profile was reconstructed.
Although the recovery rate was far from satisfactory, some results can be observed at this time.
(1) The youngest coral age is 785± 95 cal yrBP and the oldest 8150± 130 cal yrBP.
(2) The Dongsha Island is a sand cay that formed by detrital deposition entirely. No Holocene coral reef neither coral conglomerate was found underneath.
(3) The base of Holocene descends in depths from margin of the atoll toward the lagoon. The island formed on the inner (lagoon) side of the reef flat not because that’s where the water depth is shallower, but the deposition rate is faster.
(4) The reef flat on which the island sits builds up by aggradation. There is no sign of progradation, either from lagoon outward nor from ocean inward.
(5) The subsurface topography of the underlying Pleistocene limestone is consistent to the model of Purdy (1974), by which he proposed many Holocene atolls developed on antecedent platform of Pleistocene karsts.
系統號NO000005045

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