陆相湖盆大型扇三角洲沉积特征与演化规律——以准噶尔盆地玛湖凹陷西斜坡区三叠系百口泉组为例  

Sedimentary Characteristics and Evolution Law of a Lacustrine Large⁃scale Fan Delta:A case study from the Triassic Baikouquan Formation on the west slope of Mahu Sag

作　　者：蒋庆平[1] 孔垂显[1] 李维锋[2] 邱子刚[1] 卢志远[1] 常天全[1] 刘凯[1] 陈栋梁 李胜[1] 袁晓光 JIANG QingPing;KONG ChuiXian;LI WeiFeng;QIU ZiGang;LU ZhiYuan;CHANG TianQuan;LIU Kai;CHEN DongLiang;LI Sheng;YUAN XiaoGuang(Research Institute of Exploration and Development,Xinjiang Oilfield Company,PetroChina,Karamay,Xinjiang 834000,China;School of Geosciences,Yangtze University,Wuhan 430100,China;School of Geosciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国石油新疆油田分公司勘探开发研究院,新疆克拉玛依834000 [2]长江大学地球科学学院,武汉430100 [3]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《沉积学报》2020年第5期923-932,共10页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41872118)。

摘　　要：准噶尔盆地玛湖凹陷西斜坡下三叠统百口泉组内,发育了世界上罕见的、最典型的大型扇三角洲。在岩芯沉积特征观察、岩石粒度与成分分析等基础上,结合测、钻井资料等,对该大型湖相扇三角洲的沉积特征与演化规律开展系统的研究,并建立了沉积与演化模式。结果表明:百口泉组沉积时期,玛西斜坡区发育了两个大型扇三角洲,其延伸距离可大于40 km;该扇三角洲相包含扇三角洲平原、扇三角洲前缘及前扇三角洲3个亚相,以及泥石流、扇面河道、碎屑流、水下分流河道、河口砂坝及前扇三角洲泥等9个微相;该扇三角洲富含砾质,总体上以重力流沉积(泥石流和碎屑流微相)的砾岩与牵引流沉积(扇面河道和水下分流河道微相)的砾岩、含砾砂岩交替叠置为特点;前缘环境的水下分流河道延伸近二十千米,且一直保持以砾质为主;纵向上,自百一段到百三段,该扇三角洲表现为典型的连续退积式,沉积演化规律十分清楚,其中,百一段沉积时期,该扇三角洲以扇三角洲平原占据主导地位,至百三段沉积时期,该扇三角洲则演化为以扇三角洲前缘为主,得益于水下分流河道的长距离延伸,使其依然保持为大型的扇三角洲。The most typical large⁃scale fan deltas developed in the Lower Triassic Baikouquan Formation on the west⁃ern slope of Mahu Sag,Junggar Basin.Based on core observation,particle size,and composition analysis,combined with logging and drilling data,the sedimentary characteristics and evolution law of these large⁃scale lacustrine fan deltas were researched,and a sedimentary and evolutional model was established.The results showed that,during the depositional period of the Baikouquan formation,two large⁃scale fan deltas developed along the north slope of Ma⁃hu Sag,which had a distance of over 40 km.The fan delta facies can be divided into fan delta plain,fan delta front,and pro⁃delta subfacies,and further into 9 microfacies containing debris flow,braided channel,subaqueous debris flow,subaqueous distributary channel,etc..These two fan deltas were gravelly,characterized by the interbeds of gravity⁃flow conglomerates,traction⁃flow conglomerates,and gravelly sandstone.The subaqueous distributary chan⁃nels in the fan delta front environment reached nearly 20 km and always remained gravelly.Longitudinally,from the first member to the third member,these fan deltas retrograded continuously and showed a very clear sedimentary evo⁃lution law,during which the fan deltas were dominated by a fan delta plain environment during the deposition of the first member.However,they were dominated by a fan delta front environment during the deposition of the third mem⁃ber,which could still maintain large⁃scale fan deltas due to the long distances of gravelly subaqueous distributary channels.

关 键 词：百口泉组 扇三角洲 玛湖凹陷 准噶尔盆地 沉积演化 

分 类 号：P618.13[天文地球—矿床学]