郯庐断裂带辽东凸起的形成与古辽中洼陷的瓦解

辽东凸起位于郯庐断裂渤海段的北部,西邻辽中洼陷,受新生代以来郯庐断裂带双动力源和多期次幕式活动的影响,其构造演化非常复杂,特别是辽东凸起的形成时间一直未有定论。为了解决这个问题,根据构造地质学新理论和方法(断层相关褶皱和沙箱模拟),通过辽东凸起周缘断裂系统变革、地层分布、正牵引褶皱轴面变化、不整合分布和滑塌湖底扇等方面论证了辽东凸起在东营组三段沉积末期(30.3Ma)开始反转形成,并依据构造演化首次提出了"大古辽中洼陷"的存在及其瓦解。在此基础上,结合沙箱模拟实验探讨了郯庐断裂斜向拉分及其走滑活动产生了局部范围内剧烈的差异沉降促成辽东凸起的"相对隆升"。

Formation of Liaodong uplift and collapse of the ancient Liaozhong sag in Tan-Lu fault zone

Liaodong uplift is located in the northern Bohai part of Tan-Lu fault zone, adjacent to the west of Liaozhong sag. The tectonic evolution of Liaodong uplift is extremely complicated as influenced by the double dynamic source and multi-stage episodic activities of Tan-Lu fault zone since the Cenozoic. In particular, the formation period of Liaodong uplift has still not been determined. Aiming at this issue, based on new theories and techniques in tectonic geology (fault-related fold theory and sandbox simulation experiment), this study proposes that the strike-slip inversion structure of Liaodong uplift had begun to develop from the depositional stage of the third member of Dongying Formation (30.3 Ma), which is demonstrated in terms of the marginal fracture system evolution, stratigraphic distribution, axial surface inflection point of normal drag folds, unconformity distribution as well as slump and sublacustrine fans. Further, the existence and collapse of the "ancient Liaozhong sag" is first presented herein through tectonic evolution analysis, based on which it is explored using sandbox simulation experiment that the partial and intense differential settlement caused by oblique pull-apart and strike-slip activities is contributed to the "relative uplift" of Liaodong.