塔里木盆地西南坳陷白垩系层序地层与沉积充填演化

Sequence stratigraphy and sedimentary filling evolution of the Cretaceous in Southwest Depression,Tarim Basin

综合露头、测钻井资料的对比,建立了塔里木盆地西南坳陷南天山和西昆仑山前带白垩系层序地层格架。依据区域性不整合面和区域性沉积相突变界面将研究区白垩系划分为2个二级层序;依据沉积相变化、地层叠加样式的转换面以及沉积旋回结构划分出4个三级层序。通过区域内野外露头和单井等资料的分析,共识别了冲积扇、辫状河、曲流河、辫状河三角洲及曲流河三角洲等5种主要沉积相。系统地编制了各层序的沉积体系展布图,揭示了沉积体系的空间展布及纵向演化。研究表明,白垩纪塔里木盆地西南坳陷沉积范围和沉积体系有明显变化。沉积范围先由山前带向盆内扩展,反映了研究区整体上发生了较大规模的海进事件。沉积体系的演化整体上表现为陆相—海相沉积的变化过程。

Based on the comprehensive correlation of outcrops data, logging data and drilling data, we estab- lished the Cretaceous sequence stratigraphic framework in the piedmont zone of the south Tianshan and western Kunlun mountains in Southwest Depression,Tarim Basin.According to the regional unconformities and regional mutations in the interface of sedimentary facies, two second-order sequences of the Cretaceous in the study area were recognized, which can be further divided into four third-order sequences based on the change of sedimentary facies,transforming surface of stratigraphic accumulation type and the structure of sedimentary cycle.Based on the analysis from outcrops and wireline logging datasets in the study area,we recognized five sedimentary facies including alluvial fan, braided river, meandering river, braided river del- ta,meandering river delta.The distribution pattern of sedimentary systems for each sequence is systemati- cally studied,through which the spatial distribution and vertical evolution of depositional systems are re- vealed.Studies show that the deposition scope and the depositional systems had changed significantly in Cretaceous in Southwest Depression.The large-scale sea transgression events were generally proved by the evidence that the sedimentary scope changed from piedmont belt to intra-basin in the study area.The sedi- mentary systems showed an overall evolution process from continental sedimentation to marine deposition.