南海南部礼乐盆地结构演化及其对区域地质背景的响应

运用丰富的二维地震资料,通过构造结构与地层结构的分析,对礼乐盆地的盆地结构演化与转型过程及其对南海地区复杂动力学背景的响应特征进行研究。结果表明:受控于NNE、NEE、NW和近EW向的断裂体系,礼乐盆地现今构造格局表现为"两坳一隆"的结构特征;两个关键的区域角度不整合T70和T50将礼乐盆地新生界自下而上划分为三层结构:陆缘裂陷层、漂移裂陷层和前陆-拗陷层;响应于太平洋板块俯冲、印度-欧亚板块碰撞、新南海扩张、古南海消亡和菲律宾海板块楔入等一系列周缘板块重组事件,礼乐盆地的盆地结构演化及转型经历了三个阶段:陆缘多幕裂陷阶段,盆地结构受控于NNE和NEE向断裂体系,南北坳陷连通;漂移裂陷阶段,NNE和NW向共轭断裂体系控制盆地格局,中部隆起形成,分隔南、北坳陷;前陆-拗陷阶段,前陆盆地结构形成,随后盆地因热沉降进入拗陷沉积阶段。

Structural Evolution of the Liyue Basin in Southern South China Sea and Its Response to the Regional Geological Background

The Liyue basin in the northeast of the southern margin of South China Sea (SCS) experienced complex tectonic evolution in Cenozoic, resulting in the differences of basin structures in different periods. Using abundant 2D seismic data and structural and stratigraphic analysis, this paper studied the evolution and transition process of basin structure, and their response to the complicated dynamic background of the South Sea region. The results show that controlled by the NNE , NEE , NW and nearly EW trending fault systems, the Liyue basin is characterized by two depressions (South Depression and North Depression) and one uplift (namely, the Central Uplift). Two regional angular unconformities T70 and T50 unconformities divide into the Cenozoic stratigraphy into three layers, continental rifting layer, drift rifting layer and foreland depression layer. They responded to a series of reconstruction events of peripheral plates, such as Pacific plate subduction, India Eurasia plate collision, new South Sea expansion, ancient South Sea perish, and the Philippine Sea plate wedge, etc. The structural evolution of the Liyue basin experienced three stages, continental episodic rifting stage with the basin structure controlled by NNE and NEE trending faults and the Southern Depression connected with the Northern Depression; drift rifting stage with the basin controlled by NNE and NW trending faults and the newly formed Central Uplift separating the Southern Depression from the Northern Depression; foreland depression stage with the basin shown as a foreland basin structure and quick depression deposition. The characteristics and evolution of basin structure were closely related to the complex dynamic background and recorded the response in the southern margin of SCS to the tectonic events, including the convergence of the Pacific, Eurasian and Indian Australian plates, the proto SCS subduction, seafloor spreading of SCS and rotation of Philippine Sea Plate.