蒙古国塔木察格盆地塔南凹陷南屯组—大磨拐河组沉积特征

Sedimentary characteristics from Nantun Formation to Damoguaihe Formation in Tanan Sag of Tamutsag Basin

为深入研究塔木察格盆地塔南凹陷南屯组—大磨拐河组沉积环境,基于盆地演化和沉积构造背景等多种资料,利用3种沉积相标志划分南屯组—大磨拐河组的沉积相类型,分析垂向沉积演化序列、沉积相平面展布和物源位置及变化。研究结果表明:南屯组—大磨拐河组发育三角洲、湖泊和水下扇3种沉积相,细分出7种沉积亚相和10种沉积微相;受构造活动的影响,不同构造单元之间沉积相展布具有相对独立性,同一构造单元内垂向沉积序列具有一定的继承性;基于沉积盆地的伸展作用,南屯组—大磨拐河组平面上发育多种沉积体系类型,沉积充填与演化明显受不同构造幕控制,划分为2～3个物源区,受控于盆地演化和同生断层活动,南屯组—大磨拐河组物源区位置和物源供应量有所变化;平面上南屯组(早期)呈现"窄盆、深水"特点,以水下扇—扇三角洲—三角洲沉积体系为主,大磨拐河组呈现"广盆、浅水"特点,形成三角洲—湖泊沉积体系。研究成果可完善研究区沉积体系建设并指导下步勘探开发工作,分析方法可为其他区块沉积特征研究提供借鉴。

In order to deeply study the sedimentary features from Nantun Formation to Damoguaihe Formation in Tanan Sag of Tamutsag Basin, based on the following data i.e. the basin evolution, sedimentary structure background and so on, with the help of three kinds of sedimentary facies marker, the sedimentary facies types were classified for the two formations stated above, and moreover the vertical sedimentary evolution sequence, planar distribution of the sedimentary facies, the location and change of the source area were analyzed. The study results show that three kinds of the sedimentary facies including delta, lacustrine and subaqueous fan were developed from Nantun Formation to Damoguaihe Formation, and furthermore seven sedimentary subfacies and ten microfacies were divided in detail;influenced by the structural activities, the distribution and spread of the sedimentary facies among different structural units show relative independent, the vertical sedimentary sequence within the same unit possesses a certain inheritance;based on the spreading action of the sedimentary basin, multiple sedimentary system types are developed planarly in the two formations, the sedimentary infill and evolution are obviously controlled by different structural phases, two or three source areas are divided, duo to the control of the basin evolution and contemporaneous fault activities, the location of the source area and the supply amount of the source are changed;in horizon, Early Nantun Formation is characterized by “narrow basin and deep water”, the subaqueous fan-fan delta-delta sedimentary system is the main form, while Damoguaihe Formation is featured by “wide basin and shallow water”, the delta-lacustrine sedimentary system is generated. The study results can improve the construction of the sedimentary system in the study area and guide the next exploration and development, the analyzing method can provide the reference for the study of the sedimentary characteristics in the other region.