六盘山盆地新生界沉积微相与沉积演化

Sedimentary microfacies and evolution of Cenozoic Liupanshan Basin

为研究六盘山盆地新生界沉积微相特征与沉积演化规律,以盆地周缘野外露头岩性、沉积构造与沉积微相特征为研究对象,对六盘山盆地新生界沉积微相与沉积演化进行研究。结果表明,六盘山盆地新生界发育始新统寺口子组、渐新统清水营组、中新统彰恩堡组与干河沟组,与下伏不同时代地层不整合接触;六盘山盆地新生界沉积相为冲积扇、辫状河、三角洲、湖泊及沙漠沉积;根据砂、泥沉积在纵向上的组合特征,识别出砂泥薄互层式、厚泥厚砂式、薄泥厚砂式、厚泥薄砂式4种沉积充填样式;受青藏高原隆升的影响,六盘山盆地填充初始期寺口子组以辫状河冲积扇为主,在横向和纵向上变化较大,高峰期清水营组蒸发强烈,以膏盐等碎屑岩为特色的湖相沉积为主,衰退期彰恩堡组南部以湖相为主,北部以河流相为主,消亡期干河沟组自下而上砾石增多,以河流相为主,整个新生界沉积微相反映了六盘山盆地新生代沉积演化过程。研究结果对六盘山盆地新生界沉积微相与沉积演化规律有了新认识,也为不同层位、不同沉积盆地的研究提供借鉴。

In order to study the characteristics of Cenozoic sedimentary microfacies and sedimentary evolution of Liupanshan Basin,the Cenozoic sedimentary microfacies and sedimentary evolution of Liupanshan Basin are studied based on the lithology,sedimentary structure and sedimentary microfacies characteristics of outcrops around the basin.The results show that the Cenozoic in Liupanshan Basin developed the Sikouzi Formation of Eocene,the Qingshuiying Formation of Oligocene,the Zhangenbao Formation of Miocene and the Ganhegou Formation,which were in unconformity with the underlying strata of different ages.The Cenozoic sedimentary facies in Liupanshan Basin are alluvial fan,braided river,delta,lake and desert deposits.According to the combination characteristics of sand and mud deposition in the longitudinal direction,four kinds of sedimentary filling styles are identified:sand and mud thin interlayer type,thick mud and sand thick type,thin mud and sand thick type.Influenced by the uplift of the Tibetan Plateau,the Sikouzi Formation was dominated by braided river-alluvial fans during the initial filling period of the Liupanshan Basin,which varied greatly in both transverse and longitudinal aspects.During the peak period,the Qingshuiying Formation was dominated by lacustrine sediments characterized by clastic rocks such as salt and salt.During the decline period,the Zhangenbao Formation was dominated by lacustrine facies in the south and fluvial facies in the north.The whole Cenozoic sedimentary microfacies reflects the Cenozoic sedimentary evolution of Liupanshan Basin,mainly fluvial facies.The results of this study provide a new understanding of the sedimentary microfacies and sedimentary evolution of the Cenozoic in Liupanshan Basin,and provide reference for the study of different strata and sedimentary basins.