摘要： 通过大量的野外剖面观察和盆地内钻井岩心的详细描述,综合测井资料,从岩石类型、结构、沉积构造、古生物化石及测井曲线响应特征等方面对鄂尔多斯盆地及周缘地区下二叠统太原组和山西组沉积相特征进行了全面分析研究。结果表明,太原组主要发育陆棚、海岸、冲积扇和三角洲等沉积相,海岸沉积相包括障壁岛、潟湖和潮坪沉积,三角洲沉积相可划分为三角洲平原、三角洲前缘和前三角洲沉积。山西组主要发育冲积扇、河流、曲流河三角洲、湖泊和海岸沉积相,其中河流沉积相包括辫状河和曲流河沉积,曲流河三角洲沉积相可划分为曲流河三角洲平原、曲流河三角洲前缘和前三角洲沉积,而湖泊沉积相以浅湖沉积为主,海岸沉积主要为潟湖沉积。太原期,海相沉积占主导,主要分布于银川—榆林北部一线以南广大地区,并且从东西两侧至中部地区由浅海陆棚沉积和滨浅海过渡为潟湖沉积和潮坪沉积,其间发育障壁岛。盆地西北缘发育冲积扇和扇三角洲沉积,北部广大地区以三角洲沉积为主,自北向南依次为三角洲平原和三角洲前缘沉积。山西期,海水从盆地东南部退却,整体演变为海陆过渡相沉积,盆地北部乌达—杭锦旗—鄂尔多斯一线发育冲积扇沉积,向南至靖边一带依次发育辫状河和曲流河沉积,靖边以南至延安以北地区以三角洲平原沉积为主,向南至同心—庆阳一线发育三角洲前缘沉积,盆地南部彭阳—泾阳地区主要为浅湖沉积,再向南发育物源来自南部的三角洲沉积,在东南部武乡—义马一带为潟湖沉积。

关键词: 沉积相, 沉积亚相, 下二叠统, 太原组, 山西组, 鄂尔多斯盆地

Abstract: Based on the extensive field profile observation and detailed description of drilling cores in the basin,rock type and texture,sedimentary structure,paleontological fossils and logging curve response characteristics are analyzed to reveal the sedimentary characteristics of the lower Permian Taiyuan and Shanxi Formations in Ordos Basin and its adjacent areas. The result shows that the main sedimentary environments of the Taiyuan Formation are shelf,coast,alluvial fan and delta,in which the coastal sedimentary facies includes barrier island,lagoon and tidal flat. The delta facies can be divided into delta plain,delta front and prodelta. Alluvial fan,river,meandering river delta,lacustrine and coast are the main sedimentary facies in the Shanxi Formation. Fluvial facies includes braided and meandering river deposits,and the later can be divided into meandering river delta plain,meandering river delta front and prodelta deposits. The lacustrine is dominated by shallow lake deposits and the coast is dominated by lagoon deposits. During the Taiyuan sedimentary period,the marine sediments are dominant and distribute in a wide area to the south of Yinchuan and Yulin. The sedimentary environment has transitioned from shallow sea shelf in the eastern and western area,to lagoon and tidal flat in the central area,with barrier island developed in the middle. Alluvial fan and fan delta deposits are developed in the northwestern margin of the basin,and delta deposits are dominant in the vast areas of the north. The delta facies has changed from delta plain to delta front from north to south. During the sedimentary period of Shanxi Formation,sea water receded from the southeast part of the basin and evolved into marine continental transitional facies. Generally,the sedimentary environment has changed from alluvial fan(Wuda-Hangjinqi-Ordos area of the northern basin of basin),to braided and meandering river(Wuda-Hangjinqi-Ordos extend southward to Jingbian area),to delta plain(Jingbian to Yan'an), delta front(extend southward to Tongxin-Jingbian area), and to shallow lake(Pengyang-Jingyang area in the south of the basin). To the south of Pengyang-Jingyang area,the shallow lake deposited were replaced by delta deposits due to the sediment flux from the southern basin margin. The southern part of the Ordos Basin,Wuxiang-Yima area,was lagoon environment.

Key words: sedimentary facies, sedimentary sub-facies, lower Permian, Taiyuan Formation, Shanxi Formation, Ordos Basin

中图分类号: 

• P531