鄂尔多斯盆地南部延长组湖相水道-朵状体浊积扇沉积模式  

Depositional model of deep lacustrine sediment gravity flow deposits with well developed channels and lobes in Yanchang Formation,southern Ordos Basin

作　　者：庞军刚 常梁杰 国吉安 楚美娟[3] 马治国 王梓萱 王欣月 PANG Jungang;CHANG Liangjie;GUO Ji′an;CHU Meijuan;MA Zhiguo;WANG Zixuan;WANG Xinyue(Shaanxi Key Laboratory of Petroleum Accumulation Geology, School of Earth Science and Engineering,Xi′an Shiyou University, Xi′an 710065, China;No.2 Comprehensive Geophysical Prospecting Brigade Shaanxi Geological Mining Co., Ltd., Xi′an 710016, China;3 Changqing Oil Field Branch Company of China Petroleum, Xi′an 710021, China)

机构地区：[1]西安石油大学地球科学与工程学院/陕西省油气成藏地质学重点实验室,陕西西安710065 [2]陕西地矿第二综合物探大队有限公司,陕西西安710016 [3]中国石油天然气股份有限公司长庆油田分公司,陕西西安710021

出　　处：《西北大学学报（自然科学版）》2022年第1期144-158,共15页Journal of Northwest University（Natural Science Edition）

基　　金：中国地质调查局矿产资源调查评价项目(121201011000150014);地质矿产调查评价项目(21201011000150014);“十三五”国家科技重大专项(2016ZX05050006);西安石油大学科研创新团队资助项目(2013KYCXTD03);西安石油大学研究生创新与实践能力培养计划资助项目(YCS19213079)。

摘　　要：为研究鄂尔多斯盆地上三叠统延长组深湖重力流的沉积特征及其沉积模式,利用钻井岩心,周缘野外露头及钻井测井资料,识别出深水区的块状砂岩、具撕裂屑块状砂岩、平行层理砂岩、沙纹交错层理粉砂岩、同生变形构造粉砂岩、水平层理粉砂岩、块状泥岩等7种岩相类型,代表了浊流沉积(高密度、低密度)、碎屑岩、滑塌岩、深水原地沉积等成因类型;其沉积微相分为水道、堤岸/漫溢、前缘朵体和水道间/深湖泥4种。研究认为,鄂尔多斯盆地南部延长组为一种深湖水道型重力流,由斜坡区向顺着水道延伸方向(或者由水道轴部向侧翼方向),水道的下切侵蚀作用逐渐变弱,水道成因的中厚层砂体发育,且往往垂向上叠置;在水道前端发育朵状体沉积,且侧向迁移频繁,形成了大面积分布、垂向上叠置的中薄层砂体。该研究建立了研究区湖相水道-朵状体的浊流沉积模式,可为研究区深水区的砂体精细刻画提供依据,从而进一步追踪湖底水道砂体及(部分)朵状体沉积。To analyze the characteristics and further propose the depositional model of deep-lake sediment gravity flow deposits preserved in Upper Triassic Yanchang Formation of Ordos Basin;eight lithofacies types,including massive sandstone,massive sandstone with rip-up mud clasts,parallel bedding sandstone,ripple cross bedding siltstone,contemporaneous deformation siltstone,horizontal bedding siltstone and massive mudstone,were identified,based on such data as field outcrop,borehole and well-logs;which can be the constituent facies elements for turbidits(deposition from high density or low density),slump deposits,debrites,deep-water in-situ deposition.Forthermore,forur sedimentary facies/lithofacies associations:channel,levee/overflow,lobe,inter channd/deep lake mud.It is considered the sediment gravity flow with well-developed deep lake channel were widely developed in the southern Ordos Basin;in which from the slope area to the deep lake,along the elongating orientation of the channel(or from the axis to flank of the main channel),the capacity of downward erosion of the channel are progressively weakening,and the medium-thick bedded sand body of the channel well developed and commonly superimposed each other;alternatively,the lobes developed in the front of the channel basinward,and their frequently lateral migration,resulting in the medium-thin bedded sand body with large area distribution and often vertical superposition.The depositional model of turbidity current deposits characteried by channel and lobe in study area was established,which can afford the basis knowledge for the fine characterization of sand body in deep water area in the study area,the depositions of channel sandbodies and(partially)lobate sand bodies in lake bottom can be further traced in the future.

关 键 词：岩相类型 沉积相 水道 朵状体 浊积岩 深湖沉积 延长组 鄂尔多斯南部 

分 类 号：P531[天文地球—古生物学与地层学]