鲁西大汶口地区全新世临沂组沉积物粒度分布特征及地质意义

Particle Size Distribution Characteristics of Sediments in Holocene Linyi Formation in Dawenkou Basin in Shandong Province

摘要:

出露于大汶口盆地的临沂组为一套第四系松散堆积物，上部以土黄色、灰黄色含砂质粉砂、粉砂质粘土为主，下部为砂砾石层，是大汶口盆地内河流演化过程中的沉积响应和物质记录。通过对临沂组进行研究，可以反演大汶口盆地第四纪以来的沉积区水动力环境、物质运移方式和沉积环境。该文在区域地质调查工作的基础上，结合粒度分析频率曲线、概率累积曲线、粒度参数和沉积物宏观特征，对临沂组的沉积相、沉积环境和沉积韵律进行了研究。研究表明，大汶口地区临沂组下部为河床亚相边滩沉积微相，上部为河漫亚相河漫滩沉积微相，经历了由简单高能→复杂中能中低能→简单中低能→复杂中低能的水动力沉积环境变化。另外依据岩石组合特征，将其划分为4个明显的沉积韵律和1个不明显的沉积韵律组。

Abstract:

Linyi formation exposed in Dawenkou basin is a set of Quaternary loose deposits. The upper part is mainly composed of soil yellow, grayish yellow sand bearing silt and silty clay. and the lower part is composed of gravel layer. It is a sedimentary response and material record in the river evolution process in Dawenkou basin. By studying Linyi formation, hydrodynamic environment, the way of material migration and the sedimentary environment of sedimentary area in Dawenkou basin since Quaternary have been inversioned. On the basis of regional geological survey, combining with the frequency curve of particle size analysis, probable accumulation curve, grain size parameter and sediment macroscopic characteristics, sedimentary facies, sedimentary environment and sedimentary rhythm of Linyi formation have been studied. It is showed that the lower part of Linyi formation in Dawenkou is the sedimentary microfacies of subfacies and beaches of river bed; while the upper part is the sedimentary microfacies of the river diffuse subfacies river beach. It has experienced the change of hydrodynamic sedimentary environment from simple high energy→complex middle low energy→simple medium low energy→complex medium and low energy. In addition, according to the characteristics of rock assemblage, it is divided into 4 obvious sedimentary rhythms and 1 not obvious sedimentary rhythm group.