渤海湾盆地新生代以来构造-热演化模拟研究

Tectono-thermal modeling of the Bohai Bay Basin since the Cenozoic

渤海湾盆地是华北最大的新生代裂谷盆地,具有最完整的新生代地层记录,是研究盆地演化的理想区域.本文基于二维多期拉张模型,对渤海湾盆地内9条地震解释剖面进行新生代构造-热演化模拟,以揭示盆地拉张强度及热演化的时空差异性,为探讨盆地演化的地球动力学机制提供依据.研究结果表明:渤海湾盆地各坳陷新生代期间的总拉张系数为1.28～2.39,渤中坳陷和辽东湾坳陷的总拉张系数最大,而辽河坳陷和临清坳陷的拉张系数最小.盆地基底热流在古近纪中、晚期达到峰值71～100mW·m-2,之后逐渐降低至现今.盆地西部热流峰期出现的时间早于东部.由盆地拉张系数和基底热流的研究结果得出,渤海湾盆地新生代的拉张有着自西向东,自南向北的迁移,与沉积、沉降中心的迁移方向一致.太平洋板片新生代期间的幕式向东后撤可能是造成渤海湾盆地幕式拉张及拉张中心向东迁移的主要动力学机制.

The Bohai Bay Basin(BBB)is the largest Cenozoic rifted basin with the most complete Cenozoic succession compared to other basins in North China.Therefore,it is an ideal region for studying basin evolution.In this paper,tectono-thermal modeling is performed along nine seismic profiles of the BBB to reveal the spatial and temporal differences of the extension intensity and thermal evolution,which can provide evidence for the geodynamic mechanism of basin evolution.The modeling results show that the total stretching factors for different depressions in the BBB range from 1.28 to 2.39,with the largest value in the Bozhong and Liaodong Bay depressions and the minimum in the Liaohe and Linqing depressions,respectively.The basin basement heat flow reached its peaks during the middle-late Paleogene with values of 71~100 mW·m^-2,and then the basin cooled down during the remaining Cenozoic era.The arrival of heat flow peak was earlier in the west than that in the east of the basin.The modeling results of the extension factor and basement heat flow indicate that the stretching center of the BBB migrated from west to east and from south to north during the Cenozoic,which is consistent with the migration of the depocenters and subsidence centers.We infer that the episodic eastward retreat of the Pacific slab might be the main dynamic mechanism for the episodic extension and eastward migration of stretching centers in the basin.