辽中凹陷反转构造及其对郯庐断裂带走滑活动的响应

辽中凹陷发育多种样式的反转构造,其形成演化与郯庐断裂带辽东湾段新生代的脉动式活动有直接关系。通过最新的地震剖面、相干体切片等资料以及平衡剖面恢复等方法,对辽中凹陷反转构造的几何学形态、演化过程和反转期次进行研究,并结合区域板块活动背景,分析反转构造演化过程及其对郯庐断裂带新生代活动的响应。结果表明:辽中凹陷发育反转断裂、反转背斜、泥底辟、隐伏凸起等多种类型的反转构造,且沿郯庐断裂带呈带状展布。辽中凹陷在新生代主要曾经历了三期构造反转,分别发生在沙三段沉积末期、东营组沉积末期和明化镇组沉积末期。三期构造反转均与郯庐断裂带的走滑压扭活动有关,从根本上受控于周边板块活动背景的变化:第一期反转是由于太平洋板块俯冲方向和速率发生变化,导致郯庐断裂带由左旋走滑转为右旋走滑,由走滑张扭转为走滑压扭,形成反转构造的雏形;第二期反转的动力主要来源于太平洋板块对中国大陆向西的推挤作用,导致渤海湾地区受到整体挤压以及郯庐断裂带发生走滑压扭,使反转构造定型;第三期反转是由于太平洋板块的加速俯冲促使郯庐断裂带晚期再次发生走滑压扭活动,对早期反转构造进行改造。其中沙三段和明化镇组沉积末期的反转为局部反转,强度较弱,东营组沉积末期的反转为区域反转,强度最高。

The inversion structures within Liaozhong depression and its responds to the strike-slip activities of Tan-Lu fault zone

Various inversion tectonics are discovered in Liaozhong depression. Utilizing the latest seismic sections, coherency time slice and balanced cross-section restoration method, to research the geometry characteristics, evolutionary process and inversion stages of these inversion tectonics. In addition, their responses to Tan-Lu fault zone's episodic activities in Cenozoic are also analyzed by combining the regional plate activities background. The results show that: the inversion structures in Liaozhong depression mainly consist of inversion fault, inversion anticline, mud diapir and buried uplift, and represent ribbon-shaped distribution along the Liaodong bay segment of Tan-Lu fault zone. Liaozhong depression has experienced three stages of tectonic inversions respectively occured at the end of Shahejie-3 member, Dongying and Minghuazhen formations deposition periods, all of them are closely related to the transpression of Tan-Lu fault zone, and fundamentally dominated by the variation of surrounding plates activities background. The first stage of tectonic inversion was triggered by the tranformation of Tan-Lu fault zone from tanstension to transpression induced by the variation of subduction direction and rate of the Pacific plate, and formed the rudiment of inversion tectonics. The dynamics of the seond stage of tectonic inversion derived from the overall compression of Bohai Bay area and the transpression of Tan-Lu fault zone induced by the westward compressional stress of the Pacific plate to Chinese Mainland, and promoted the shaping of different types of inversion tectonics. The third stage of tectonic inversion was induced by the resurrection of Tan-Lu fault zone in late period caused by the accelerating suduction of the Pacific plate, and rebulided the pre-existing inversion stectonics. Among these the first and third inversions were developed in localized area and weak, while the second inversion was developed in regional area and respectively violent.