南祁连盆地阳康地区二叠系—三叠系沉积特征

Sedimentary characteristics of Permian-Triassic in Yangkang area, South Qilian Basin

采用野外地质剖面实测与岩石薄片鉴定等方法,综合运用地层学、沉积岩石学及含油气盆地分析等理论,对南祁连盆地阳康隆起及周缘地区二叠系—三叠系岩石组合类型、沉积相演化特征进行了研究。研究区主要由阳康隆起、哈拉湖坳陷、下日哈坳陷3个构造单元构成,中二叠统—上三叠统地层发育完整,岩性多变,沉积相包含了碳酸盐岩台地相、浅海陆棚相、滨岸相、三角洲相、河流相及湖泊相,具有2个明显的沉积旋回,对应2次大规模的海进和海退沉积。研究区构造演化是决定其沉积演化的关键因素,自加里东运动以来,阳康隆起就一直以古隆起形式存在,控制着整个二叠纪—三叠纪沉积古地理环境,阳康隆起自晚志留世之后再未接受沉积,仅在哈拉湖坳陷和下日哈坳陷沉积了二叠系—三叠系。

The field geological profile measurement and the thin section identification of rocks were used,combined with stratigraphy,sedimentary petrology and petroliferous basin analyses,to study the rock assemblage types and sedimentary facies evolution of the Permian-Triassic in the Yangkang Uplift and its surrounding areas,the South Qilian Basin.The study area is mainly composed of three tectonic units:the Yangkang Uplift,the Halahu Depression and the Xiariha Depression.The Middle Permian to Upper Triassic strata were well developed and lithologically variable.The sediments include carbonate platform,shallow shelf,littoral,delta,fluvial and lacustrine facies.There are two distinct sedimentary cycles,corresponding to two large-scale transgressive and regressive deposits.The tectonic evolution of the study area is the key factor determining its sedimentary evolution.Since the Caledonian Movement,the Yangkang Uplift existed as a paleo-uplift,which controlled the whole Permian-Triassic sedimentary paleogeographic environment.The uplift has not received sediments since the Late Silurian,and only includes Permian-Triassic strata in the Halahu Depression and the Xiariha Depression.