东海陆架盆地西部坳陷中—新生界构造特征

东海陆架盆地西部坳陷为整个盆地内重要的二级构造单元之一，发育有多个次级凹陷，完整记录了盆地及周边晚白垩世以来的构造变形信息，能够为解决太平洋板块俯冲、东亚陆缘类型转换等相关科学问题提供参考。基于二维地震剖面解释，并综合前人研究成果，通过对东海陆架盆地西部坳陷的构造分析认为，该坳陷发育有中—新生界两大构造层，由一系列中—新生代裂陷盆地组成，为早白垩世晚期应力场由挤压环境转换为拉张伸展环境下的产物，以伸展构造样式为主，半地堑、掀斜断块、多米诺式断裂等上述伸展构造样式发育。同时，伴随晚白垩世末期的应力反转，坳陷内长江凹陷局部可见有正反转构造样式。坳陷内断裂展布具有不同时期、方向不同、性质各异的特征，而岩浆岩发育则表现出了广泛分布、不同时代、规模和岩性各异的特点，二者皆与区域构造方向基本一致。白垩纪以来，太平洋板块的漂移方向、俯冲角度的多次变化为坳陷现今中—新生代构造格局形成的主要因素，此外后期菲律宾海板块向欧亚板块的碰撞、挤压、俯冲作用使得整个构造格局更加复杂化。

MESO-CENOZOIC TECTONIC FEATURES OF THE WESTERN DEPRESSION OF THE EAST CHINA SEA SHELF BASIN

The Western Depression(WD), one of the important secondary tectonic units in the East China Sea Shelf Basin(ECSSB), is composed of many subordinate sags. It plays a key role in understanding the tectonic deformation in the ECSSB and adjacent areas since Late Cretaceous and in provision of references in the study of the Pacific subduction, conversion of continental margin type and other related scientific issues. Based on the seismic data interpretation and previous studies, we analyzed the structure framework of the WD in this paper. Both the Mesozoic and Cenozoic tectonic layers are well developed in the WD, and they are characterized by a series of Meso-Cenozoic extensional structural styles, such as half-grabens, titled faulted blocks, domino faults and so on, formed in late Cretaceous due to transformation of stress field from compression to extension. Meanwhile, along with the stress inversion at the end of Late Cretaceous, the positive inversion tectonic patterns also can be seen in the Changjiang Sag of the WD. The distribution patterns and features of faults in the WD vary with time, while the magmatic rocks change in distribution area, time, scale and lithology. Both faults and magnetic rocks are distributed upon the regional tectonic direction. Since Cretaceous, the drifting direction and the subduction angles of the Pacific Plate have become the main factors for the formation of the Mesozoic and Cenozoic tectonic structures in the WD. In addition, the collision, compression and subduction of the Philippine Sea Plate to the Eurasian Plate have made the tectonic pattern more complicated.