松辽盆地外围西部上二叠统林西组岩相古地理特征

Lithofacies palaeogeography characteristics of Upper Permian Linxi Formation in the western periphery of Songliao Basin

松辽盆地外围西部上二叠统林西组主要分布于西拉木伦河断裂以北、贺根山—黑河断裂以南,以及稍北的内蒙古地区。根据野外勘察、实测剖面和岩心观察资料,建立研究区上二叠统林西组沉积亚相岩性组合模式,明确晚二叠世林西组岩相古地理特征。结果表明:研究区上二叠统林西组主要发育湖泊、扇三角洲、河流3种沉积相,以及滨浅湖、半深湖、扇三角洲平原、扇三角洲前缘、辫状河、滨浅海6种沉积亚相,以滨浅湖亚相为主,滨浅海亚相分布局限,在林西县官地剖面顶部出现。松辽盆地西部上二叠统林西组,构成以西拉木伦河与贺根山—黑河断裂为主要控制区的、以南北向物源供给为主的滨浅湖—扇三角洲—河流沉积体系。该结果对松辽盆地外围西部晚古生代油气勘探具有重要意义。

In the western periphery of Songliao Basin,the Linxi Formation is mainly distributed on the north of the Xilamulun River,south of the Hegen Mountain-Hei River Faults and in the Inner Mongolia Region on the north.In this paper,authors set up a lithology combination model of Permian series Linxi Formation sedimentary subfacies in research area,and defined the lithofacies palaeogeography characteristics of Upper Permian through a lot of field geological explorations and section measurements.The results indicate that there are three types of sedimentary facies in the Upper Permian Linxi Formation:lake facies,fan delta facies and river facies.There are also 6 kinds of sedimentary subfacies,including semi-deep lake subfacies,fan delta plain subfacies,fan delta front subfacies,braided river subfacies littoral shallow sea subfacies and littoral shallow lake subfacies mainly.The offshore subfacies coastal and shallow marine facies distribut limited,only at the top of the profile in Linxi county magistrate.In the western periphery of Songliao Basin,the distribution of Linxi Formation is mainly controlled by the Xilamulun River and Hegen Mountain-Hei River Faults.The main sources of supplyment are from south and north.It forms a shallow lake-fan delta-river sedimentary system.This result is of great significance for Late Paleozoic oil and gas exploration in the western periphery of Songliao Basin.