西南坳陷主要发育两套滑脱层序,一套是中寒武统和田河组膏盐岩,另一套是古近系底部阿尔塔什组和齐姆根组的夹灰岩、白云岩的膏泥岩;前者厚度500m左右,后者厚度在100—700m左右。和田河组膏盐岩主要影响中生代及中新世末的构造变形,古近系底部的膏泥岩主要影响上新世末及第四纪的构造变形,构造变形样式均以顺层滑脱构造为主,它们在空间上常常表现为构造叠加和构造组合,滑脱构造与其它构造变形样式在剖面上组成4类构造组合:1)与滑脱相关的断层传播褶皱;2)叠瓦式滑脱构造;3)楔入构造+被改造的断层相关褶皱;4)滑脱断层+断层相关褶皱。前两类构造组合主要发育于麦盖提斜坡及其周缘,后两类构造组合主要发育于山前冲断带,本文建立了这些构造组合样式的构造模型,它们对于山前带或盆地内复杂区块的构造解释、圈闭落实具有指导意义。
There are two decollement strata in southwestern depression of Tarim Basin :one is 500 m Middle Cambrian salt-gypsum layer, and another is 100 - 700 m Lower Paleogene gypsum mudstone with limestone and dolostone. The Middle Cambrian salt-gypsum layer is mainly related with Mesozoic and Late Miocene structural deformation, however, the Lower Paleogene gypsum mudstone is mainly involved in Late Pliocne and Quaternary structural deformation. The decollement structure is the most important structural style. The decollement structure and other structural styles consist of four kinds of structural assemblages in section : 1 ) decollement fault related fold; 2) imbricated decollement structure ; 3 ) wedging structure + reconstructed faultrelated fold; 4) detachment fault + fault related fold. The former two structural assemblages mainly distribute in Maigaiti slope and its periphery,and the latter two structural combinations mainly distribute in fold and thrust belt of western Kunlun Mountain. The structural modes of these structural styles are set up, which are significant to structural interpretation and identification of traps of complicated areas in southwest Tarim Basin.