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Extension and inversion of salt-bearing rift systems
Solid Earth ( IF 3.2 ) Pub Date : 2020-07-06 , DOI: 10.5194/se-11-1187-2020
Tim P. Dooley , Michael R. Hudec

We used physical models to investigate the structural evolution of segmented extensional rifts containing syn-rift evaporites and their subsequent inversion. An early stage of extension generated structural topography consisting of a series of en-échelon graben. Our salt analog filled these graben and the surroundings before continued extension and, finally, inversion. During post-salt extension, deformation in the subsalt section remained focused on the graben-bounding fault systems, whereas deformation in suprasalt sediments was mostly detached, forming a sigmoidal extensional minibasin system across the original segmented graben array. Little brittle deformation was observed in the post-salt section. Sedimentary loading from the minibasins drove salt up onto the footwalls of the subsalt faults, forming diapirs and salt-ridge networks on the intra-rift high blocks. Salt remobilization and expulsion from beneath the extensional minibasins was enhanced along and up the major relay or transfer zones that separated the original sub-salt grabens, forming major diapirs in these locations. Inversion of this salt-bearing rift system produced strongly decoupled shortening belts in basement and suprasalt sequences. Suprasalt deformation geometries and orientations are strongly controlled by the salt diapir and ridge network produced during extension and subsequent downbuilding. Thrusts are typically localized at minibasin margins where the overburden was thinnest, and salt had risen diapirically on the horst blocks. In the subsalt section, shortening strongly inverted sub-salt grabens, which uplifted the suprasalt minibasins. New pop-up structures also formed in the subsalt section. Primary welds formed as suprasalt minibasins touched down onto inverted graben. Model geometries compare favorably to natural examples such as those in the Moroccan High Atlas.

中文翻译:

含盐裂谷系统的扩展和反演

我们使用物理模型研究了包含同裂隙蒸发物的分段伸展裂谷的结构演化及其随后的反转。扩展的早期阶段生成了由一系列en-chelon抓斗组成的结构地形。我们的盐类似物充满了这些被抓的东西和周围的环境,然后继续延伸,最后反转。在盐下后延伸过程中,盐下剖面的变形仍集中在bound陷边界断层系统上,而超盐沉积物的变形大部分被分离,在原始的分段grab陷阵列上形成了一个S型伸展小盆地系统。在盐后段几乎没有观察到脆性变形。小流域的沉积物将盐分带到盐下断层的下盘,在裂谷内高块上形成辉石和盐脊网络。沿主要接力区或转移区的上方和向上加强了从延伸小流域下面的盐的迁移和驱逐,这些区域将原始的次盐抓斗分开,在这些位置形成了主要的底栖生物。这种含盐裂谷系统的反转产生了基底和超盐岩层序中强烈分离的缩短带。超盐岩的变形几何形状和方向受到伸展和随后的下扩建过程中产生的盐底辟和脊网的强烈控制。推力通常局限在小盆地的边缘,那里的上覆层最薄,盐在绝地块上逐渐增加。在盐下段,缩短了强烈倒置的盐下grab陷,这抬高了超盐下小盆地。盐下部分中还形成了新的弹出结构。上超微盆地上形成的初级焊缝触及倒grab。模型的几何图形与自然示例(例如摩洛哥高等地图集)的示例相比具有优势。
更新日期:2020-08-20
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