东海西湖凹陷中深层逆冲断层系统与原型盆地重建

The Pinghu and Huahu Formations develop in the medium-deep stratum of the Xihu Sag, East China Sea. What kind of the proto-basin type of the Xihu Sag during the deposition of the both formations and its origin are critical scientific questions for a long time in the research field on Eastern Chinese basins. In this project, we implement an integrated analyses of tectono-stratigraphy-deposition and basin modeling to reveal the proto-type of Xihu Sag, its dynamic background and the subsidence mechanism in upper-crustal and near-surface settings by combination of the pattern of thrust fault system in medium-deep stratum, significant unconformities of the tectonic origin, the magnitude of deformation, structural styles and depositional patterns, the systematic migration of depocenter, sedimentary provenance signature, thermo-tectonic evolution and the kinematic reorganization of adjacent plates and so on. This study aims to propose a new tectonic model for the Xihu Sag which will help to promote scientific progress on understanding the evolution of rifting valley system controlled by the convergent plate tectonic systems. Moreover, the proto-basin reconstruction for the Xihu Sag will be absolutely important for petroleum exploration in East China Sea.

围绕西湖凹陷中深层平湖组-花港组沉积时期盆地原型及其成因属性这个核心科学问题，通过构造-层序地层-沉积多学科交叉以及静态分析和动态模拟相结合的研究思路和方法，从西湖凹陷中深层逆冲断层系变形组合样式、构造变革界面、构造变形量、构造-沉积型式、沉降中心迁移规律、物源特征、构造热演化和周缘板块运动重组事件分析等方面揭示西湖凹陷的原型盆地结构、发育的动力学背景及岩石圈表层沉降机制，明确原型盆地的地质成因属性。本研究力求从新的角度重建西湖凹陷的动力学演化过程，有助于进一步深化汇聚板块背景下裂谷盆地的发育模式，并对该凹陷的油气勘探有实际应用价值。

以海域盆地油气勘探开发中积累的丰富的地质地球物理资料为基础，详细解释和分析了东海陆架盆地西湖凹陷新生代构造地层格架，划分出弧后前陆盆地的演化阶段，认识到区域挤压作用对该盆地演化过程的重要性。区域板块运动学分析表明，晚始新世发生的全球板块运动重组事件导致了中国近海海域盆地构造的差异性演化。该事件发生之前，中国东部处于欧亚板块和太平洋板块相互作用构建的“双板块”动力体制之下，太平洋板块的俯冲后退作用导致了欧亚板块陆缘弧后伸展，形成了广布中国东部大陆边缘的盆岭式断陷盆地系。该区域板块构造事件之后，由于太平洋板块俯冲方向的转变和菲律宾海板块的楔入使东海陆架盆地的演化不像南海那样持续伸展直到裂解分离，反而进入长期的弧后前陆盆地演化阶段，其中，西湖凹陷处于该前陆盆地的前渊沉降单元，直到上新世开始才进入区域性的沉降过程。海域盆地是我国重要的油气生产基地，本项目成果不仅进一步深化了中国海域盆地的形成演化过程和动力机制的认识，而且对于该区的油气勘探和开发也具有重要的实际应用价值。