Sedimentary dynamics and depositional model for mud accumulation in deep lake basins:A case study in the Upper Triassic Chang-7 Member,Ordos Basin,northern China

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外文摘要：Shales in deep lake basins have become the main focus of continental shale oil and gas explo-ration.In order to highlight the sedimentary dynamics of mud deposition in deep lake basins,a combination of core observation,thin section examination,X-ray diffraction,and QEMSCAN(quantitative evaluation of minerals by scanning electron microscopy)was used to analyze the depositional characteristics of mudrocks in the Chang-7 Member from the Yanchang Formation(Upper Triassic)in Ordos Basin,and to establish a depo-sitional model for mud accumulation in deep lake basins.This study recognizes four mudrock lithofacies in the Chang-7 Member:(1)the laminated silt-bearing mudstone,which generally develops a binary composition of"silt-clay"or a ternary composition of"silt-clay-organic matter";(2)the graded mudstone,mainly composed of dark gray and gray-black mudstone sandwiched by silt-bearing mudstone;(3)the massive mudstone,internally showing a uniform distribution of quartz,clay,and carbonate minerals,with also a small amount of organic detritus;and(4)the laminated shale,which is generally composed of clay laminae,and organic laminae of the former two.Sediment supply,topographic slope,and flood intensity combine to control the evolution of gravity flows and the transport and deposition of the mudrock in the Chang-7 Member.The influence of orogeny provides terrain gradient,water depth,abundant sediments at source areas,and trig-gering mechanism for the formation of gravity flows.Floods triggered by wetting events provide the impetus for sediment transport.Mud deposition in the Chang-7 Member was mainly related to the transport and sedimentation of mud by hyperpycnal flows and rapid sedimentation by buoyant plume flocculation.A comprehensive evolutionary model for shale accumulation in the deep lake basin is established by integrating various triggering mechanisms and mud transport sedimentary processes.

外文关键词：

MudrockSedimentary dynamics mechanismDepositional modelChang-7 MemberDepression lake basin

作者：

Wei Yu、Feng Wang、Jing-Chun Tian、Jiao Wang、Benjamin Kneller、Tian Yang、Wei-Zhen Chen

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作者单位：

College of Petroleum Engineering,Shandong Institute of Petroleum and Chemical Technology,Dongying 257061,Shandong Province,China

Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications of Ministry of Natural Resources,Chengdu University of Technology,Chengdu 610059,Sichuan Province,China

Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,Sichuan Province,China

University of Aberdeen,School of Geoscience,Aberdeen AB24 3UE,Scotland,UK

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出版年：

2024

DOI：

10.1016/j.jop.2024.08.006

古地理学报(英文版)

影响因子：0.186

ISSN：

年,卷(期)：2024.13(4)