磨圆度定量表征在扇三角洲沉积微相判别中的应用

砾石颗粒的磨圆度对粗碎屑的沉积环境具有重要的指示意义。针对玛湖凹陷下三叠统百口泉组砾岩的地下钻井岩芯，运用去扁化De?flat磨圆度测量方法，通过定量获取砾石磨圆度参数对扇三角洲沉积中不同沉积微相的指示关系，分析黄羊泉扇的磨圆度及其方差的分布特征，讨论磨圆度定量表征指示扇三角洲沉积的科学性。研究结果表明，扇三角洲沉积的砾石磨圆度普遍较差，为次棱—次圆状和次棱角状。牵引流沉积的砾石磨圆度普遍好于重力流沉积的砾石磨圆度，且牵引流沉积的砾石磨圆度方差明显小于重力流沉积的方差，指示河道沉积中的砾石磨圆度更加集中。黄羊泉扇砾石磨圆度以棱角状和次棱角状为主。通过黄羊泉扇区砾岩砾石颗粒磨圆度及其方差的变化趋势，表明磨圆度对沉积相带具有指示意义。砾石磨圆度的定量表征可以为粗粒碎屑沉积相分析提供新的定量沉积学手段。

Application of Quantitative Roundness Characterization to Identify Sedimentary Microfacies in Fan Delta Deposits: A case study of conglomerates in the Baikouquan Formation,Mahu Sag

The roundness of gravel particles is of great significance to the sedimentary facies of clastic particles. Through examining the underground drilling cores of the Lower Triassic Baikouquan Formation in Mahu Sag， using the de?flat roundness measurement， the quantitative relationship between gravel roundness and sedimentary microfacies in the fan delta deposition was obtained. In Huangyangquan fan， the distribution characteristics of roundness and their corresponding variance were analyzed， and the rationality of quantitative roundness characterization was discussed. The results show that the roundness of the gravel deposition in the fan delta is generally poor， mostly sub?angular & rounded and sub?angular. Gravel roundness by traction flow deposits is generally better than that by gravity flow deposits. Moreover， the roundness variance by traction flow is significantly lower than that by gravity flow deposits， indicating that the roundness distribution in the channel deposits is more concentrated. In Huangyangquan fan， the roundness is mainly angular to sub?angular. According to the trend of roundness and variance of conglomerate gravel particles in Huangyangquan， roundness can be an indicator of sedimentary facies. From the above， the quantitative characterization of gravel roundness could be a new quantitative sedimentology method for the analysis of coarse?grained clastic sedimentary facies.