王雪木, 陈万利, 薛玉龙, 刘刚. 西沙群岛宣德环礁晚第四纪灰砂岛沉积地层[J]. 海洋地质与第四纪地质, 2018, 38(6): 37-45. DOI: 10.16562/j.cnki.0256-1492.2018.06.004
引用本文: 王雪木, 陈万利, 薛玉龙, 刘刚. 西沙群岛宣德环礁晚第四纪灰砂岛沉积地层[J]. 海洋地质与第四纪地质, 2018, 38(6): 37-45. DOI: 10.16562/j.cnki.0256-1492.2018.06.004
WANG Xuemu, CHEN Wanli, XUE Yulong, LIU Gang. The Late Quaternary Carbonate sand deposits at the Xuande Atoll[J]. Marine Geology & Quaternary Geology, 2018, 38(6): 37-45. DOI: 10.16562/j.cnki.0256-1492.2018.06.004
Citation: WANG Xuemu, CHEN Wanli, XUE Yulong, LIU Gang. The Late Quaternary Carbonate sand deposits at the Xuande Atoll[J]. Marine Geology & Quaternary Geology, 2018, 38(6): 37-45. DOI: 10.16562/j.cnki.0256-1492.2018.06.004

西沙群岛宣德环礁晚第四纪灰砂岛沉积地层

The Late Quaternary Carbonate sand deposits at the Xuande Atoll

  • 摘要: 灰砂岛沉积能记录碳酸盐台地上地表的沉积过程,了解这些过程对于古灰砂岛沉积的资源勘探和现代岛屿的工程建设都有着重要意义。结合最新的岛上钻孔数据和近期野外地质考察结果对西沙群岛宣德环礁晚第四纪灰砂岛沉积地层的平面分布特征和纵向演化规律进行了研究,结果显示南岛的灰砂岛沉积的百年尺度沉积过程复杂,不同期次沉积相互混杂,不利于开展百年尺度的灰砂岛沉积研究。永兴岛18.39m可能为更新统和全新统的分界面,其下为珊瑚礁灰岩硬底,为灰砂岛的淹没期,其上为灰砂岛沉积时期的初始期、扩张期和稳定期,发育珊瑚、贝壳生物碎屑的松散沉积物。宣德环礁的灰砂岛沉积最早是更新世晚期暴露时(MIS4)开始形成,且主要分布在石岛,从全新世中期开始,宣德环礁其他岛屿上快速发育灰砂岛沉积。灰砂岛的形状受到季风和海岸地貌的影响显著,其主要是通过控制海滩岩的发育来影响灰砂岛形状。

     

    Abstract: Carbonate sands are the common clastic deposits formed on the surface of carbonate platforms. Understanding the depositional processes of the deposits is of great significance to the development of carbonate sand resources and the construction of modern artificial islands. On the basis of the latest drilling and geological survey data, the distribution pattern and vertical evolution of the Late Quaternary carbonate sand deposits at the Xuande Atoll, Xisha Islands are studied in this paper. The results suggest that the centennial scale depositional process is rather complex on the South Island, and the interdecadal sediments are mixed each other and not conducive to the study of centennial scale sedimentation. The boundary at 18.39m in depth on the Woody Island is defined as the boundary between Pleistocene and Holocene. The Pleistocene deposits of coral reef limestone below 18.39m were formed during the submerging period of the platform. Upon the boundary deposited the loose sediments of coral and shell bioclasts formed in the initial period, expansionary period and stable period of the coral island respectively. The bioclastic deposits at the Xuande atoll were firstly formed during glacial MIS4, mainly on the Shidao Island. A large number of coral islands appeared at the Xuande Atoll after Middle Holocene. The shape of the carbonate sand island is significantly affected by the distribution of beach rocks which are controlled by the monsoon and ocean waves.

     

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