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热带海洋学报

• • 上一篇    

南海U形海疆线的地质构造特征研究

张云帆1 , 唐丹玲2,  孙珍3,  邱宁1   

  1. 1.      热带海洋环境与岛礁生态全国重点实验室, 广东广州 510301

    2.      南方海洋科学与工程广东省实验室(广州）, 广东 广州 511458

    3.      中国科学院南海海洋研究所边缘海与大洋地质实验室, 广东广州 510301

  • 收稿日期:2025-06-04 修回日期:2025-10-10 接受日期:2025-10-15
  • 通讯作者: 孙珍
  • 基金资助:

    广东省特支计划创新团队项目(2019BT02H594)

Study on the geological structural characteristics of U-boundary in the South China Sea

ZHANG Yunfan 1, TANG Danling 2, SUN Zhen3, QIUNing 1   

  1. 1.      State Key Laboratory of Tropical Oceanography, Guangzhou 510301

    2.  Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou)， Guangzhou 510301

    3.  Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, The Chinese Academy of Sciences, Guangzhou 510301

  • Received:2025-06-04 Revised:2025-10-10 Accepted:2025-10-15
  • Supported by:
    Guangdong Special Support Talent Team Program(2019BT02H594)

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摘要： 南海U形海疆线是我国在南海的权益边界，是维护国家海洋权益和推进海洋强国战略的关键区域，认识南海U形海疆线的下伏地质构造特征具有重要科学意义。本文深入分析南海U形海疆线海底地形、自由空间重力异常和磁力异常数据，研究U形线西北、西、南、东和东北五个区间的地球物理与地质特征，并探讨其与南海演化的关系。研究发现，南海U形线（带）的海底地形为“西浅南平东深”，水深在0~5400m之间；自由空间重力异常整体与地形呈正相关，异常分布范围为-100~0 mGal，磁力异常整体呈正异常（-50~100nT），反映了海底以下岩石的磁性变化和空间赋存状态。研究还进一步揭示了U形海疆线走向与海底地貌构造单元的一致性：U形线西区段与红河断裂系统、南海西缘断裂走向一致，其中西北段和西段在走滑伸展的背景下断面结构具有挤压褶皱和负花状构造；U形线南区段与南海南部陆架坡折和南沙海槽重合，剖面构造在早-中中新世界面表现出大规模的破裂不整合特征，U形线东区段在平面上与马尼拉海沟走向一致，在断面上处于南海板块俯冲于菲律宾海板块所产生的增生楔处；U形海疆线在南海西部陆缘、东南部陆缘、东部边界都处于重力异常剧烈变化的梯度带上，代表了地形地貌的强烈起伏，是构造的边界和天然的分界线。本研究成果总结了南海U形海疆线的数据基础和地质资料，将为南海海洋划界和南海防灾减灾提供科学支撑。

关键词: 南海U形海疆线, 海洋地质构造, 重磁异常, 5区间分法

Abstract: The U-boundary in the South China Sea is the boundary of China's rights. It is a key area for safeguarding national maritime rights and interests and promoting the strategy of building a maritime power. Understanding the underlying geological structure characteristics of the U-shaped maritime border line in the South China Sea is of great scientific significance. This paper focuses on the geological structure characteristics of the U-boundary in the South China Sea, and obtains the depth of the U-boundary (belt) by using global bathymetric, gravity and magnetic data. Combined with the different nature of the boundary around the South China Sea, the structural characteristics of each section of the U-boundary are analyzed, and the relationship with the rupture and evolution of the South China Sea is analyzed. Through research, we believe that the water depth of the U- boundary (belt) in the South China Sea presents the characteristics of "shallow in the west, flat in the south, deep in the east", ranging from 0 to 5000 meters. The gravity anomaly is negative as a whole (-100 mgal-0 mGal), and there are spot-like positive anomalies affected by seamount. The positive and negative anomaly characteristics of each segment are positively correlated with the terrain. The positive magnetic anomalies in the U-boundary line (belt) of the South China Sea are positive as a whole, ranging from -50 to 100nT, reflecting the magnetic changes and spatial occurrence of the rocks below the seabed. The consistency of U-boundary line strike with submarine geomorphic tectonic units and the section characteristics of each section are also analyzed. In the west section, the strike is consistent with the Honghe fault system and the west margin of the South China Sea. The U1 and U2 sections have compressive folds and negative flower-like structures under the background of strike-slip extension. The southern U-boundary overlaps with the slope break of the southern shelf of the South China Sea and the Nansha Trough, and shows a large-scale rupture unconformity in the section of the early-Middle Sino-World plane, and the strike of the U5 section is consistent with that of the Manila Trench, and the South China Sea plate subducts under the Philippine Sea plate on the section. The U-boundary is located on the gradient zone of abnormally intense gravitational changes at the western, southeastern and eastern boundaries of the South China Sea. It represents the strong undulations of topography and landforms and serves as the boundary of structure and the natural dividing line. The data basis and geological data reference of U-boundary line are enriched to provide data support for maritime delimitation.

Key words: U-boundary of SCS, Marine geological structure, Gravity and magnetic anomaly, 5-zones distinction method of U- boundary