鄂西恩施白垩纪盆地跑马岗组砂砾岩粒度分析

Grain Size Analysis of Sand-conglomerate of Paomagang Formation in Enshi Cretaceous Basin,Western Hubei Province

粒度是沉积物和沉积岩的主要特征,反映了沉积作用的流体力学性质,是分析与对比沉积环境的依据。利用恩施白垩纪盆地跑马岗组7个砾岩样品和19个砂岩样品的粒度分析资料,通过对跑马岗组一段砾岩粒度分布参数统计分析,及跑马岗组二段砂岩粒度特征参数、粒度概率累积曲线、结构参数散点图解等分析,认为跑马岗组整体处于冲积扇-三角洲相沉积环境。在研究过程中还对跑马岗组下部和上部进行趋势分析,判定跑马岗组下部为冲积扇扇中-扇缘沉积环境,跑马岗组上部为三角洲平原-前缘沉积环境,总体为一连续过渡的沉积相模式。

Grain size is the main feature of sediments and sedimentary rocks,which reflects the hydrodynamic properties of sedimentation and is the basis for analyzing and comparing sedimentary environments. In the paper,on the basis of 7 conglomerate samples and 19 sandstone samples of the Paomagang Formation in Enshi Cretaceous Basin,the grain size distribution parameters of the first member of the Paomagang Formation are analyzed by statistical analysis,and the grain size characteristic parameters,grain size probability cumulative curve and structural parameter scatter point diagram of the second member of the Paomagang Formation are analyzed.There are distinct evidence that Paomagang formation indicates the alluvial plain-delta environment.On the comparative trends analysis of the upper and the lower Paomagang formation,it suggests that the lower indicates the alluvial fan-fan edge environment and the upper indicates the delta plains-front sedimentary environment which is a continuous transitional sedimentary facies model.