准南西段构造样式及逆冲推覆构造特征

准噶尔盆地南缘油气勘探的潜力是巨大的，但构造复杂、勘探难度大，因而运用断层相关褶皱的构造分析理论来研究该盆地南缘西段山前冲断带的复杂构造变形，有助于建立更为合理的构造解释方案，降低油气勘探的风险。为此，依据断层相关褶皱分析理论确定了该盆地南缘西段山前冲断带2种逆冲推覆构造样式，进而得出以下认识：①该盆地南缘3套构造滑脱层（中下侏罗统煤系地层、白垩系吐谷鲁群泥岩层、古近系安集海河组泥岩层）控制了南缘逆冲推覆断裂的发育特征，逆冲推覆断裂发育的层位及特征对南缘区域构造展布特征及局部构造样式都起到了明显的控制作用；②该盆地南缘山前冲断带发育2种逆冲推覆构造模式，即后翼冲断-前翼深层楔形逆冲及浅层的断层传播褶皱、后翼反冲-前翼深层断层转折褶皱及浅层的断层传播褶皱；③该盆地南缘背斜构造是多种构造样式叠加的复合背斜，南缘下组合构造圈闭与中上组合相比构造相对宽缓，勘探领域广阔。

Structural types and features in the west of south margin in the Junggar Basin

Hydrocarbon exploration has a great potential but is facing great challenge due to complex geological structures along the south margin of the Junggar Basin. In order to have a better understanding of the complex structures and mitigate the risk in hydrocarbon exploration, a structural analysis of fault related folding is made on the complex tectonic transformation in the western pledmont thrust belt of this study area. The following conclusions are drawn. (1) There are three key sets of detachment layers: a. coal strata of Middle and Lower Jurassic; b. mudstone strata of Tugulu Group of Cretaceous; and c. mudstone strata of Anjihaihe Formation of Paleogene, which completely reflect the features of thrust nappe faults there. The location and features of the developed thrust nappe faults have an important influence on the structural patterns and regional structural extension. (2) There are two thrust nappe structures in this study area. The Huoerguosi Manasi Tugulu anticlines are composed of deep wedges and the overlying mid shallow fault propagation folds. While the anticlines of Junggar foreland are composed of shallow fault propagation folds and deep fault bend folds. However, fault activity in the frontier of Qigu fault fold zone shows behavior of forward thrusting and back thrusting. Finally, it is considered that the structural styles and superimposition characteristics control the hydrocarbon distribution properties of the three accumulation combination of Junggar foreland. (3) This area is dominated by the composite anticlines composed of superimposition of different structural patterns. The structures of deep structural trap assemblages are relatively wider and flatter than those of mid shallow structures so that there is a wide exploration area in this study area.