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张倩,李文厚等——鄂尔多斯盆地侏罗纪沉积体系及古地理演化

已有 210 次阅读 2021-9-2 10:02 |个人分类:论文推广|系统分类:论文交流

鄂尔多斯盆地侏罗纪沉积体系及古地理演化

张 倩 李文厚 刘文汇 李兆雨 白金莉 杨 博

(西北大学地质学系,大陆动力国家重点实验室 西安 710069

 

摘 要 为进一步整体研究鄂尔多斯盆地侏罗纪沉积体系及古地理演化特征,笔者通过野外剖面实测、钻井资料分析并结合前人研究成果对盆地发育地层进行详细研究。研究结果表明鄂尔多斯盆地侏罗系发育有冲积扇、河流、三角洲、湖泊沉积体系。在古地理演化过程中,早侏罗世富县期沉积以填平补齐为特征,仅在河道及两侧发育河流相沉积,济源地区发育浅湖相沉积。中侏罗世延安期延10亚期开始河谷宽度扩大,高地进一步缩小,主要以河流相为主,济源湖面积有所增大,延9亚期是三角洲体系发育早期,也是最大湖侵期,盆地西部及北部仍为曲流河沉积,向南逐渐过渡到三角洲沉积,在志丹延安济源一带发育浅湖沉积;延8亚期局部构造抬升,三角洲平原进一步扩大,河流向湖泊进积;延7—延6亚期,盆地稳定填充,延4+5亚期湖泊面积缩小,延3、延2及延1亚期构造抬升,河流回春,盆地进入萎缩阶段。中侏罗世直罗期安定期在盆地周缘发育冲积平原,内部主体为河流三角洲湖泊沉积。晚侏罗世芬芳河期仅在盆地西缘发育冲积扇沉积。

关键词 鄂尔多斯盆地 侏罗纪 沉积相

Jurassic sedimentary system and paleogeographic evolution of Ordos Basin

Zhang Qian Li Wenhou Liu Wenhui Li Zhaoyu Bai Jinli Yang Bo

(State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069)

 

Abstract

In order to further study the Jurassic sedimentary facies and paleogeographic evolution of Ordos Basin, the author made a detailed study on the developed strata of Ordos Basin through field measurement, drilling data analysis and previous research results. The results show that there are alluvial fan, river, delta and lacustrine sedimentary systems in Ordos Basin during Jurassic. In the process of paleogeographic evolution, the sediment of Early Jurassic Fuxian Period were characterized by filling and leveling, only fluvial facies deposits are developed in the river channel and both sides, and shallow lacustrine facies develops are developed in Jiyuan area. During the Middle Jurassic Yanan Period, the width of the valley began to broaden and the highlands further narrowed, mainly in fluvial facies, and the area of Jiyuan Lake increased. The early development of the delta system was also the largest lake transgression stage in Yan-9. The western and northern parts of the basin was still meandering river deposition, which gradually transition to delta deposition to the south, and shallow lake deposition was developed in Zhidan-Yanan-Jiyuan area. During the Yan-7~Yan-6 subperiod, the basin was filled steadily, the lake area decreased in the Yan-4+5 subperiod, and during the Yan-3, Yan-2 and Yan-1 subperiods, the river revived, and the basin entered the shrinking stage. During Zhiluo-Anding Period of Middle Jurassic, alluvial plain was developed around the basin, and the main part of the basin was fluvial delta lacustrine deposit. In the Fenfanghe Period of Late Jurassic, only alluvial fan deposits developed in the western margin of the basin.

Keywords Ordos Basin, Jurassic, Sedimentary Facies

 

鄂尔多斯盆地侏罗纪是油、气、煤、铀等多种能源矿产形成转化的重要时期,也是盆地发展的重要时期(赵越等,2004;刘池洋等,2006;董树文等,20072008;程爱国等,2016)。前人对侏罗纪沉积体系做过较多研究,认为中侏罗世延安期为冲积沉积体系,主要为冲积扇和河流相沉积(陈庸勋等,1981;李思田等,1992;张福礼等,1994;李宝芳等,1995;张泓等,1995;赵俊兴等,1999)。富县期10亚期为冲积扇河流沉积,延9—延6亚期为三角洲湖泊沉积,延4+5亚期为网状河湖泊沉积(时志强等,2003;梁积伟,2007;杨磊,2008)。自早侏罗世富县期—晚侏罗世芬芳河期,鄂尔多斯盆地岩相古地理演化经历了河流冲积扇、湖泊沼泽、河流三角洲和冲积扇(庞军刚等,2012;李振宏,2015;郭艳琴等,2019)。从延安期到直罗期气候逐渐变干旱、炎热,处于富氧的淡水环境,直罗组顶部红层显示强氧化环境(张天福等,2016;孙立新等,2017)。侏罗纪富县组吴起地区为辫状河沉积,宁陕古河与蒙陕古河在吴起地区交汇(刘犟,2012)。盆地西南部直罗组物源来自西秦岭造山带,早期为辫状河辫状河三角洲,晚期为曲流河三角洲(赵俊峰,20072010;陈安清等,2019)。但前人仅对局部地区局部层段进行沉积环境和沉积相的研究,未对全盆全时段沉积演化做出详细描述并成图。本文在综合前人研究成果的基础上,通过野外剖面实测、岩心观察、测井资料解释等多种方法相结合对鄂尔多斯盆地侏罗纪沉积体系及古地理演化进行深入研究。

1 地质背景

经过印支运动的影响,上三叠统延长组遭遇到不同程度的剥蚀作用,造成盆地中南部西高中陷东缓的古地貌特征,侏罗系发育在区域角度不整合和起伏不平的古地形上,沉积以填平补齐为特点,与下伏上三叠统延长组呈区域不整合接触关系,富县组沉积后盆地又经历短暂抬升,造成下侏罗统富县组与中侏罗统延安组之间沉积间断接触,随后盆地正常沉积延安组,之后再次经历抬升,导致延安组与直罗组之间平行不整合微角度不整合接触,直罗组、安定组正常沉积后盆地西缘快速隆升,导致上侏罗统芬芳河组仅在盆地西缘沉积,其上与下白垩统志丹群为角度不整合接触关系(李宝芳等,1995;时志强等,2003;梁积伟,2007)。

侏罗系自下而上分为下侏罗统富县组、中侏罗统延安组、直罗组、安定组和上侏罗统芬芳河组,在盆地内主要以宝塔砂岩、裴庄砂岩、真武洞砂岩、七里镇砂岩、高桥砂岩作为对比标志层(图1)。

 

1.jpg

1 鄂尔多斯盆地侏罗系层序对比标志(据梁积伟,2007修改)

Fig. 1 Sequence correlation marks of Jurassic in Ordos Basin (modified from Liang, 2007)



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