酒泉盆地南缘山前冲断带构造特征与油气勘探方向

酒泉盆地在新生代受祁连山褶皱带由南往北的逆冲推覆作用，在横向上形成了复杂的前陆盆地结构，依次有南缘山前冲断带、南部前陆拗陷、前陆斜坡、黑山-合黎山前缘隆起和花海-金塔隆后拗陷；在纵向上表现为新生代前陆构造层叠置在中生代伸展构造层之上的双层结构特征。本文主要通过对地震剖面及地面露头资料的综合研究，重点分析了自晚第三纪以来酒泉盆地的地质结构特征、构造变形特征及下步油气勘探方向，并获得以下认识：南缘山前冲断带构造变形表现为多个逆冲推覆带侧向叠置，并且由于调节断层的分割作用，构造变形及结构具有明显的东、西分段特征，构造变形强度总体表现为西强东弱，推覆体广泛逆掩于下白垩统之上；南缘山前冲断带石油地质条件优越，是盆地内最主要的油气聚集区，其中逆冲推覆体下盘掩伏构造是下步油气勘探的主攻方向。

Structural character of frontland thrust belt of Jiuquan Basin South Margin and oil/gas exploration direction.

Because of thrust action of Qilian Fold Belt from south to north in Cenozoic,the complex foreland basin was formed laterally in Jiuquan Basin,having following structures successfully:South-Margin frontland thrust belt,South foreland depression,foreland slope,Heishan-Helishan frontal uplift and Huahai-Jinta post-uplift depression;vertically there is characteristic of double-layer structure that the Cenozoic foreland structural layer was stacked on Mesozoic strengthening structural layer.Mainly through the synthetic study of seismic sections and outcrop,the analysis in the paper centers on the characters of geologic structures and structural deformation in Jiuquan Basin since Neogene and the next oil/gas exploration direction,in which the following acknowledge is gained:the structural deformation of South-Margin frontland thrust belt is characteristic of the lateral stack of multiple thrust belts and structural deformation and structures are characterized by clear east-west segmentation because of the divide action of adjusting fault,the strength of structural deformation is generally showed as strong in west and weak in east and trust block is widely thrust above the Lower Cretaceous;oil geologic condition is superiority in South-Margin foreland thrust belt that is most important oil/gas accumulation zone in that basin,among which the thrust structure on the side of down-thrown of thrust block is main targets of next oil/gas exploration.