惠民凹陷扭张断裂与沉积耦合关系的量化表征

Quantitative characterization of the coupling relationship between transtensional faults and sedimentation in Huimin Sag

惠民凹陷为典型的扭张盆地,临商、夏口2组帚状断裂带控制了凹陷内主要沉积体系的发育。基于地震、地质等基础资料,提出了扭张断裂瞬时活动性的量化表征方法,建立了扭张盆地断裂-沉积耦合演化模式。研究表明,惠民凹陷沉积背景结构可划分为帚状撒开端稳定缓坡、帚状收敛端同沉积断坡和帚状收敛端持续迁移下陷缓坡等3种类型。不同沉积背景结构中,体系的差异不仅体现在发育的空间位置上,也体现在沉积过程的时间曲线中。帚状撒开端稳定缓坡断裂生长速率平缓,幕式活动不明显,沉积速率相对稳定;帚状收敛端同沉积断坡断裂幕式活动明显,沉积速率受生长速率变化影响而波动;帚状收敛端持续迁移下陷缓坡断裂沉积速率持续缓慢增加,也受到断裂幕式活动的影响。

Huimin Sag is a typical transtensional basin,in which the two sets of brush-shaped faults named Linshang and Xiakou control the development of major sedimentary systems.Based on seismic data and geological data,a quantitative characterization method for instantaneous activity of transtensional fault is proposed,and a fault-sedimentary coupling evolution model is established for transtensional basin.Studies show that the sedimentary background structure in Huimin Sag can be divided into three types:the stable gentle slope in the brush-shaped divergent end,the synsedimentary break slope in the brush-shaped convergent end and the continuous migration and subsidence gentle slope in the brush-shaped convergent end.In different sedimentary background structures,the differences are not only reflected in the spatial position,but also in time curve of sedimentary process.Fault activity rate in the stable gentle slope of the brush-shaped divergent end is comparatively stable without obvious episodic fluctuation,and the deposition rate is also relatively stable.The episodic fault activities is the main feature for synsedimentary break slope in the brush-shaped convergent end,and deposition rate fluctuates with fault activity rate.The continuous migration and subsidence gentle slope of the brush-shaped convergent end results in a continuous and slow increase in deposition rate,which is also affected by episodic fault activities.