琼东南盆地古近纪裂陷构造特征及其动力学机制

琼东南盆地是发育在南海北部大陆边缘西北部的新生代沉积盆地，经历了始新世-早渐新世和晚渐新世两期的伸展作用，形成了半地堑和地堑两种裂陷构造样式以及“南北分带、东西分段”的裂陷结构特征。从力学和岩石圈伸展角度分析了琼东南盆地形成的动力学机制，提出始新世-早渐新世盆地的裂陷作用是在印支地块旋转挤出相关的左行旋转力和东侧古南海俯冲产生的近南南东向拉伸力联合作用下发生的，而晚渐新世盆地伸展作用的主要构造动力是南海海底扩张；认为岩石圈热状态直接制约了上地壳伸展方式，北部坳陷带在相对冷岩石圈环境下发生伸展裂解，形成以半地堑构造为主的单断式裂陷带，而中央坳陷带在相对热岩石圈环境下发生伸展裂解，形成由半地堑和地堑组成的复式裂陷带。图12参23

Paleogene rift structure and its dynamics of Qiongdongnan Basin

Qiongdongnan Basin is a Tertiary basin developed on the northwest margin of the South China Sea; it experienced two stages of extension from Eocene to early Oligocene and during late Oligocene. Two styles of structures, half-graben and graben, developed with zonation from north to south and segmentation from east to west. From the point of mechanics and lithospheric extension, both the sinistral rotational stress associated with the Indosinian plate extrusion and the SSE stretching stress caused by the sub-duction of the ancient South China Sea controlled the rifting of Qiongdongnan Basin from Eocene to early Oligocene, while the extension during late Oligocene was caused by the spreading of the subsea basin. The thermal situation of the lithosphere determined the stretching style of the upper crust. The northern depression developed half-grabens controlled by synclined faults due to relative cold lithosphere extension, while the central depression is characterized by composite rift belts, which are composed of half-graben and graben.