泌阳凹陷下第三系的层序地层格架及其对边界断裂、古气候和物源的响应

Lower Tertiary Sequence Stratigraphy Framework and Its's Response to Boundary Faults, Paleoclimate and Sediment Source in Biyang Depression

根据详细的相分析、地震地质解释及区域地质方面的研究,把泌阳凹陷内的下第三系划分为3个层序,依次代表湖盆的3个演化阶段.层序Ⅱ_1和层序Ⅱ_3分别是湖盆初陷阶段和萎缩阶段的产物,均为由冲积平原体系域和硫酸盐湖体系域构成的半旋回式二元结构,体现了干旱气候条件下湖盆的冲积-充填特征,但湖盆初陷阶段的边界断裂活动强度比湖盆萎缩阶段要大.层序Ⅱ_2为湖盆主陷阶段的产物,由湖进体系域、碳酸盐湖体系域和湖退体系域构成的一个完整的沉积旋回.在湖盆主陷阶段,气候较潮湿,边界断裂活动强度大,但因物源及边界断裂活动强度的差异,湖盆不同部位发育的沉积体系类型及规模明显不同.

On the basis of detailed fades analysis, seismology interpretation and regional geologic survey, the Lower Tertiary in Biyang Depression is divided into three sequences which represent three evolutionary stages of the lake basin. Sequences Ⅱ1 and Ⅱ3, the products of initial depression stage and shrinking stage, are semicycles composed of alluvial plain and sulphate lake system tracts. Boundary faults were more active in initial depression stage than in shrinking stage. Sequence Ⅱ, the product of major depression stage, is a complete cycle consisting of lacustrine transgression, carbonate lake and lacustrine regression system tracts. In major depression stage, boundary faults were the most active and paleoclimate was moist, but deposi-tional - system types and their scale were different in every parts of the lake basin because of disparity in boundary fault activity and sediment source.