鄂尔多斯盆地东部地区早奥陶世马家沟期沉积模式探讨

上奥陶统马家沟组为鄂尔多斯盆地东部最重要储集层,目前关于该区早奥陶世马家沟期沉积模式及岩相古地理存在较大争议.本次研究运用现代岩相古地理分析方法,以钻探成果资料与微量元素分析、镜下鉴定等分析化验资料为依据,重建了其沉积模式.指出马一、三、五亚期为海退期,盆地东部与外海隔离,气候干热,主要发育膏盐湖与含膏云坪的沉积组合;马二、四亚期为海侵期,发育开阔海、局限海与云灰坪沉积组合.并结合岩相古地理特征,以低海平面时期和高海平面时期分别建立鄂尔多斯盆地东部早奥陶世马家沟期沉积模式.

Dissussion on the Lower Ordovician Majiagou Formation of Eastern Ordos Basin

The Lower Ordovician Majiagou formation is the most important reservoir in eastern Ordos basin.There are some arguments about lithofacies paleogeography and sedimentary model of this area during the Early Ordovician.According to the data of drilling,trace elements analysis,thin sections identification,and sedimentary facies analysis,it suggests that Ma1,Ma3,Ma5 are characterized by a dry and hot climate as well as fall of the sea level,the anointed salt lake and gypsum-bearing dolomitite flat are mainly developed.During the stage of Ma2 and Ma4,Seawater covers all the area,and the climate is wet and hot with rising sea level,the open marine,restricted marine,dolomitic and limemud flat are mainly developed.Combined with lithofacies paleogeographic characteristics,the sedimentary model of Majiagou formation in the Early Ordovician of eastern Ordos Basin is established,according to low sea level and high sea level period.