Afghan-Tajik depression: Architecture of sedimentary cover and evolution
Afghan-Tajik depression: Architecture of sedimentary cover and evolution
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DOI：
10.2205/2002es000106
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发表时间：
2002-11
影响因子：
1.3
通讯作者：
V. Nikolaev
中科院分区：
文献类型：
--
作者：
V. Nikolaev
讨论的是一个独特的新生代特征，阿富汗-塔吉克凹陷，横跨塔吉克斯坦、阿富汗和乌兹别克斯坦的地区。这项研究利用了CMP剖面图(区域和勘探尺度)、钻探和其他地质和地球物理证据，以及大量已公布的数据。大多数数据，特别是地震数据，都是第一次发布。构造图显示了沉积盖层不同层位的深度和推断的结晶基底的深度。盐下地层与上覆磨拉石组合存在构造不匹配。盐下构造特征更加均匀、平缓。磨拉石组合以各种类型的褶皱为主，包括等斜褶皱，并伴有逆冲和推覆。以前，褶皱被认为在北部的加姆山谷地区会聚，并向南发散。这一概念是过分关注平安日河以北地区(即前苏联领土)而忽视阿富汗领土结构的产物。考虑整个阿富汗-塔吉克凹陷，主要是它的新生代部分，人们发现磨拉石组合的阿尔卑斯型褶皱形成了向西的凸弧。该弧形始于Garm附近，终止于Alburz-Mormul EW向断裂的水平。在北部和南部，凹陷的边界是杜尚别和阿富汗北部的板凳，这些板凳高于凹陷的内部，并被赤道高地和盆地改变。新生代褶皱的弧形排列表明，其成因与沿盐层顶部的滑脱有关。这种拆离可能是由于帕米尔地块对空地的西向压力，因为帕米尔地块的平均高度约为4公里，而阿富汗-塔吉克斯坦凹陷的沉积物表面海拔在0-100-200m之间，因此褶皱是由结晶岩体膨胀造成的侧向挤压控制的，而不是由地壳块体沿一个或另一个方向移动控制的。
Discussed is a singular Cenozoic feature, the Afghan-Tajik depression, spanning areas located in Tajikistan, Afghanistan, and Uzbekistan. The study draws on CMP profiling (regional and prospect scale), drilling, and other geological and geophysical evidence, and also a wealth of published data. Most of the data, especially seismics, are published for the first time. Structural maps showing depth to various horizons of sedimentary cover and depth to the inferred crystalline basement have been constructed. Structural mismatch exists between subsalt strata and the overlying molasse assemblage. Subsalt structural features are more equant and gentle. The molasse assemblage is dominated by various types of folds, including isoclinal, accompanied by overthrusts and nappes. Formerly, the folds were believed to converge in the Garm valley region on the north and to diverge southward. This concept is an artifact of overmuch focusing on the area north of the Pyandzh River (i.e., the Former USSR territory), while ignoring the structure of the Afghan territory. While considering the entire Afghan-Tajik depression, primarily its Cenozoic portion, one finds that Alpine-type folds of the molasse assemblage make a westward convex arc. This arc begins near Garm and terminates approximately at the level of the Alburz-Mormul EW-trending fault. On the north and south, the depression is bounded by the Dushanbe and north Afghan benches, elevated above the depression's interior and modified by equant highs and basins. The arcuate arrangement of Cenozoic folds suggests that their origin was related to detachment along the top of salt strata. This detachment may have been due to the westward pressure from the Pamir block against an empty space, because the average height of the Pamir block is ca. 4 km, and the surface of sediments of the Afghan-Tajik depression has elevations between 0 and 100-200 m. Consequently, folding was controlled by lateral compression due to expansion of crystalline rock mass, and not by crustal blocks moving in one or another direction.