依据野外露头、岩心观察、测井等资料综合分析将鄂尔多斯地区马家沟组划分为6个三级层序和12个体系域,在此基础上对马家沟组层序地层学特征进行分析,采用体系域压缩法编制了层序岩相古地理图.结果表明:盆地沉积演化受西南缘祁连海和东部华北海共同影响,两者在OSQ4(奥陶系马家沟组第4个层序,下同)期完全贯通,西南缘具陆缘海沉积特征,东部为陆表海沉积.OSQ1、OSQ2、OSQ3、OSQ5海侵体系域局限台地发育,高位期局部形成膏盐岩湖;OSQ4、OSQ6海侵、高位期均为开阔台地相,西南缘高位期发育台地边缘滩和台地边缘生物礁.OSQ1、OSQ3、OSQ5高位体系域白云岩及OSQ6高位体系域西南缘生物礁和颗粒滩可成为重要的油气储集体,OSQ3、OSQ5高位体系域发育的膏盐岩形成了2套重要的区域盖层.%The Majiagou Formation in Ordos Basin can be divided into 6 third-order sequences and 12 system tracts on the basis of field profile, core and well log. In this paper, characteristics of sequence stratigraphy of Majiagou Formation were analyzed, sequence-based lithofacies and paleogeography were also compiled by means of condensation of mapping units of sedimentary system tracts. It is indicated that the basin sedimentary evolution was controlled by the North China Sea and the Qilian Sea, with the former being an epeiric sea and the latter being an epicontinental sea. OSQ1, OSQ2, OSQ3 and OSQ5 are mainly restricted platforms in TST,and some areas are anointed lakes in HST; open platform is the main fades of OSQ4 and OSQ6 whether in TST or HST; reef and shoal are formed in HST of southwest margin. Dolomites of HST in OSQ1, OSQ3, OSQ5 and southwest reef and shoal might be important oil-gas reservoirs, and gypsum of HST in OSQ3 and OSQ5 forms 2 major regional caps of Ordos Basin.
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