Evolution of the Late Miocene atoll systems offshore Xisha Islands
Evolution of the Late Miocene atoll systems offshore Xisha Islands
复制标题
西沙群岛近海晚中新世环礁系统的演化
DOI：
10.1007/s11430-014-4962-9
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Sha ZhiBin
中科院分区：
文献类型：
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作者：
Kuang ZengGui;Guo YiQun;Wang LiaoLiang;Liang JinQiang;Sha ZhiBin
对南海现代环礁进行了系统而深入的研究。然而，对古环礁和相关沉积系统的了解非常有限。本文利用新获得的高分辨率二维地震资料，首次在西沙群岛近海发现了三个晚中新世环礁系统。我们将它们分别命名为环礁系统A、B、C。这三个环礁体系均发育在以正断层为主的地垒之上，主要由环礁礁、斑礁、礁前斜坡沉积和泻湖组成。根据层序地层格架的解释和礁前斜坡沉积的识别，认为上新世只有A环礁系统继续发育至第四纪，而B和C环礁系统均已被淹没。晚中新世是研究区环礁系统最发育的时期，无论是规模还是成熟度，都表明晚中新世是造礁者最活跃的时期，这与南海ODP 184航次的钻探结果相一致。上新世是研究区重要的礁淹没期，B、C两个环礁系统均被淹没，半远洋沉积逐渐盛行。第四纪是研究区另一个礁淹没期，A环礁系统上生长的两个大型环礁礁最终被淹没，半远洋沉积物开始覆盖和填充古环礁系统。环礁的生长和淹没在长期内主要受构造沉降的控制，但在短期内全球海平面变化也会对环礁的生长和淹没产生影响。
Modern atolls have been studied systematically and thoroughly in the South China Sea. However, the knowledge of a paleo-atoll and related sedimentary system is very limited. Here we used the newly acquired high resolution 2D seismic data, and discovered three late Miocene atoll systems in the offshore Xisha Islands for the first time. We named them atoll system A, B, C, respectively. These three atoll systems, all developed on the horsts dominated by normal fault, consist mainly of atoll reefs, patch reefs, fore-reef slope deposits, and lagoons. On the basis of the interpreted sequence stratigraphic framework and the identification of fore-reef slope deposits, we suggested only the atoll system A continued to grow until Quaternary, and both of atoll system B and C had been drowned in Pliocene. In late Miocene, the atoll systems in the study area were most developed, either in magnitude or in maturity, which indicated late Miocene was the most flourishing period of reef builders, and this was in accordance with the drilling result of ODP Leg 184 in the South China Sea. Pliocene was an important reef drowning period in the study area, and both atoll systems B and C were drowned and hemipelagic deposits prevailed gradually. Quaternary was another reef drowning period in the study area, two large atoll reefs grown on the atoll system A were finally drowned, and hemipelagic deposits begun to drape and fill the palaeo-atoll systems. The growth and drowning of atolls are controlled mainly by tectonic subsidence in long term, but global eustatic can impact it in short term also.