南堡凹陷分期异向伸展变形叠加特征:来自砂箱物理模拟实验的启示

Deformation Superimposition Characteristics Resulting from Stretching Direction Changes in Nanpu Sag: Insight from Physical Modeling

在前人关于南堡凹陷新生代断裂系统形成机制构造物理模拟实验的基础上,针对南堡凹陷典型沉积时期断裂系统分布规律,进一步细化、分阶段开展了研究区不同沉积时期的构造在不同先存基底条件下的平面砂箱物理模拟实验,探讨了南堡凹陷新生代断裂系统形成的主控因素。研究结果表明:(1)南堡凹陷新生代构造具有分期异向伸展变形叠加的特征,是两期不同伸展方向构造变形叠加的产物;(2)NE—SW向断裂系统是在沙河街时期近NW—SE向伸展作用下形成的;近E—W向断裂系统是自东营期以来在近SN向伸展作用下形成的;东营早期是南堡凹陷应力体制发生转变的关键时期;(3)不同沉积时期的构造形态受控于特定的边界几何条件、基底非均匀性及先存断裂的展布特征。

According to the comparison of the previous modeling results and the actual geological conditions in Nanpu sag,different series of physical models which are in different stretching directions and different pre-exist-ing basin structures have been conducted.Furthermore,the Cenozoic fault systems in Nanpu sag are discussed. The results can be concluded as follows:(1 )The Cenozoic fault systems in Nanpu sag are the result of two-phase extensions with different stretching directions. (2 )The NE-SW fault systems had undergone NW-SE extension during the Shahejie depositional period;while the EW fault systems had undergone SN extension since Dongying depositional period.The early Dongying period witnessed the changes of regional stress direction of Nanpu sag.(3 )The structural characteristics in different depositional periods were controlled by particular boundary geometry,basal heterogeneity,and distribution of pre-existing faults.