鄂尔多斯盆地中南部上古生界层序与岩相古地理演化_李克永.pdf

书书书第 25 卷第 1 期2023 年2 月古地理学报JOUNAL OF PALAEOGEOGAPHY(Chinese Edition)Vol.25No.1Feb 2023文章编号:16711505(2023)01007518DOI:107605/gdlxb202301006鄂尔多斯盆地中南部上古生界层序与岩相古地理演化*李克永1杨文鹏1徐帅康1李文厚21 西安科技大学地质与环境学院/期刊中心，陕西西安 7100542 西北大学地质学系/大陆动力学国家重点实验室，陕西西安 710069摘要为明确鄂尔多斯盆地中南部上古生界层序特点与岩相古地理演化规律，利用周缘野外露头和盆地钻井测井相特征，分析层序界面、体系域界面的岩性、古构造及海侵方向变化特征，总结层序发育特点与岩相古地理演化规律。结果表明:不同风化序列的区域性不整合面及海侵方向转换面为二级层序界面，区域性海退面、下切冲刷面及陆上暴露面为三级层序界面;潮间带砂坪及近岸相海侵含砾砂岩顶为海侵面，最大海侵面发育灰岩、泥页岩及煤层，是海侵体系域与高位体系域分界面;上古生界包括二级层序 2 个:MSQ1、MSQ2，三级层序 6 个:SQ1、SQ2、SQ3、SQ4、SQ5、SQ6，其中 SQ1SQ2 发育水进体系域与高位体系域，不发育低位体系域，SQ1 为潟湖障壁海岸沉积体系，SQ2 为泥炭坪泥坪相潮坪沉积;SQ3SQ6 发育完整的低位海侵高位体系域，SQ3 发育区域性海退进积海陆过渡相三角洲沉积，SQ4 早期为低位体系域下切冲蚀砂体，晚期沉积古环境由温暖湿润还原环境演变为炎热干燥的氧化环境，SQ5SQ6 早中期为氧化环境三角洲沉积，SQ6 晚期为高位体系域具海侵夹层的潮坪相沉积。研究为鄂尔多斯盆地及其他盆地层序与岩相古地理演化提供理论依据。关键词区域性不整合面层序地层体系域岩相古地理鄂尔多斯盆地第一作者简介李克永，男，1970 年生，博士，硕士生导师，主要从事沉积学和石油地质学专业等方面研究工作。E-mail:。中图分类号:P531文献标志码:A*国家科技重大专项(编号:2017ZX05005002004)资助。Financially supported by the National Science and Technology Major Project(No 2017ZX05005002004)收稿日期:20220411改回日期:20221006Sequence stratigyaphy and lithofacies palaeogeography evolution ofthe Upper Paleozoic in central-southern Ordos BasinLI Keyong1YANG Wenpeng1XU Shuaikang1LI Wenhou21 School of Geology and Environment/Periodical Center，Xian University of Science and Technology，Xian 710054，China2 Department of Geology/State Key Laboratory of Continental Dynamics，Northwest University，Xian 710069，ChinaAbstractIn order to classify the stratigraphic sequence characteristics and lithofacies palaeogeogra-phy evolution of the Upper Paleozoic in the central-southern Ordos Basin，the development and variationcharacteristics of lithology，paleostructure and transgression direction of sequence boundary and systemtract interface were analyzed by using field outcrops and drilling logging facies in the basin The character-istics of sequence development and lithofacies palaeogeography evolution were summarized The results古地理学报2023 年 2 月showed that the regional unconformity surface and transgressive direction conversion surface of differentweathering sequences were the second-order sequence boundary，and the regional regression surface，scouring surface and subaerial exposure surface are the third-order sequence boundary The sand flat of in-tertidal zone and the top of coastal transgression gravelly sandstone were transgression surfaces，and thetypical lithology of the maximum transgressive surface were limestone，shale and coal seam，which werethe interface between transgressive systems tract and highstand systems tract The Upper Paleozoic includestwo second-order sequences MSQ1 and MSQ2，and six third-order sequences SQ1，SQ2，SQ3，SQ4，SQ5 and SQ6 Among them，SQ1SQ2 did not develop lowstand systems tract，but only develop trans-gressive systems tract and highstand systems tract，and SQ3SQ6 developed complete lowstand-transgres-sion-highstand systems tract;The lagoon-barrier coastal sedimentary system developed in SQ1，the tidalflat sedimentary system developed in SQ2 and the transitional delta sedimentary system developed in SQ3In the early stage of SQ4，the downcutting sand body developed in the lowstand systems tract In the latestage of SQ4，the sedimentary environment evolved from warm and humid reduction to hot and dry oxida-tion environment In the early and middle stages of SQ5SQ6，the delta front developed in the oxidationenvironment，and in the late stage of SQ6，the tidal flat developed in the highstand systems tract withtransgression interlayer The investigation provides a theoretical basis for the study of sequence and lithofa-cies paleogeographic evolution in the Ordos Basin as well as in other basinsKey wordsregional unconformities，sequence strata，system tracts，lithofacies palaeogeography，Ordos BasinAbout the first authorLI Keyong，born in 1970，is a Ph.D.and postgraduate tutor in Xian U-niversity of Science and Technology He is mainly engaged in sedimentology and petroleum geologyE-mail:鄂尔多斯盆地中南部晚古生代由陆表海向海陆过渡相、陆相湖盆演化。上古生界野外露头和测井曲线区域性不整合面、区域性海退面、下切冲刷面、海侵方向转换面、陆上暴露面等层序界面特征明显，海侵面、最大海泛面等体系域界面易于识别，便于利用层序地层学分析上古生界地层发育特征，利用岩性岩相等地质特征恢复岩相古地理。邵龙义等(2018)将鄂尔多斯盆地东部本溪组、太原组和山西组划分为 3 个三级层序，海侵方向由北东向转变为南东向;常嘉等(2019)根据华北地区不同类型层序界面将上古生界划分为 7 个三级层序;侯中帅等(2018a)依据层序界面将盆地东部上古生界划分为 7 个三级层序，并将不同体系域类型与沉积相带对应;罗立民等(1997)、张周良(1996)、方石等(2000)等认为辫状河为水退阶段低位体系域，曲流河向网状河演变阶段为水进体系域，曲流河沉积类型为高位体系域。对华北地区及鄂尔多斯盆地上古生界不同范围、不同层位、不同尺度的层序及岩相古地理进行研究(郭 英 海 等，1998;陈 世 悦，2000;邵 龙 义 等，2009;张满郎等，2009;鲁静等，2012;侯中帅等，2018;常嘉等，2021)，但研究多服务于寻找油气资源，造成研究区域和研究层位存在一定局限性，导致鄂尔多斯盆地相关成果认识不尽统一。利用鄂尔多斯盆地中南部钻井及盆地周缘野外露头层序界面、体系域界面特征，对鄂尔多斯盆地中南部上古生界层序地层进行划分，分析岩相古地理特征及沉积演化规律，恢复盆地中南部上古生界古地理环境，为分析鄂尔多斯盆地演化规律提供依据。1区域地质背景鄂尔多斯盆地位于华北地台西部，是华北克拉通次一级构造单元，北起阴山、大青山，南至秦岭，东起吕梁山、太行山，西至贺兰山、六盘山，盆地面积为 37104km2，是中国第二大沉积盆地(杨俊杰和裴锡古，1996)。本次研究范围北至鄂托克旗、保德，东临盆地东部边界，西至泾源、平凉一带，南至渭北隆起南部，地跨陕北斜坡、晋西67第 25 卷第 1 期李克永等:鄂尔多斯盆地中南部上古生界层序与岩相古地理演化挠褶带、天环坳陷、西缘逆冲带、渭北隆起等 5 个一级构造单元(图 1)。图 1鄂尔多斯盆地构造分区及研究区位置图Fig.1Structural partition and study area location in Ordos Basin鄂尔多斯盆地自中晚奥陶世隆起之后至晚石炭世接受海侵，加里东运动后半期为主造山幕，华北地块与西伯利亚板块全面碰撞，阴山燕山造山带快速隆升使华北地块挤压坳陷形成沉积盆地。盆地西缘、东部和南部分别受祁连海、华北