鄂尔多斯盆地西部奥陶系古岩溶类型及主控因素

Paleokarst Types and Main Controlling Factors of Ordovician in Western Ordos Basin

野外剖面、岩心观察和镜下薄片鉴定揭示鄂尔多斯盆地西部奥陶系桌子山组、克里摩里组古岩溶储层非常发育。系统建立了研究区3种古岩溶作用的识别标志,将古岩溶划分为(准)同生期古岩溶作用、表生期顺层古岩溶作用和埋藏期古岩溶作用等三大类型,并以表生期顺层古岩溶作用为主。一级层序界面对应奥陶系顶部的风化壳古岩溶面,三级层序对(准)同生期古岩溶作用和表生期顺层古岩溶作用起控制作用;SQ6、SQ7和SQ8等3个I型层序底界面附近古岩溶作用相对较发育,层序格架内古岩溶发育段主要处于高位体系域和海侵体系域。在对鄂尔多斯盆地奥陶系地质背景分析的基础上,认为区内古岩溶发育的主控因素包括层序、构造条件、岩性特征、古气候条件及古地貌。

By means of detailed outcrop observation, core observation and thin section, it is indicated that the solution caves developed well in Zhuozishan Formation, Kelimoli Formation in western Ordos Basin. Three kinds of identification marks were established by systemic study of paleokarsts. We classified the paleokarst into is three types ： syngenesis karsti- fication, supergene bedded karstification and burial karstification, and the supergene bedded karstification was the main. The first order sequence corresponds to the weathering crust karst surface at the top of Ordovician, and the third order se- quence controls syngenesis and supergene bedded karstification. The karstification relatively developed nearby the bottom of SQ6, SQ7 and SQS. The karstification of sequence framework is relatively developed in SQ2, SQ5 and SQT. The karstifica- tion section mainly belongs to the highstand system tracts and transgressive system tracts. On the basis of analyzing the geo- logical background of Ordovician in Ordos Basin, we believed that the main controlling factors of paleokarst development in- cluded sequence, structural condition, lithology, paleo climate and paleokarst landform.