Shaping the crustal structure of the SW-Alpine Foreland: Insights from 3D Geological modeling

IF 2.7 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
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Abstract

Reactivation processes play a significative role in the localization of deformation but still remain hard to establish at the lithospheric scale. In this work, we built a 3D structural model, which enables to bridge the gap between the main tectonic structures observed at the surface and the geometry of the major interfaces (the Mohorovičić-discontinuity (hereafter Moho) and top of the basement) inferred from geophysical data acquired in the external Western Alps and their foreland. The geometry of these tectonic structures is interpreted in relation to their geodynamic evolution. The main results of this study highlight: (1) a strong contribution of thick-skinned Pyrenean-Provence and Alpine tectonics, (2) a lithospheric rooting of Variscan shear zones and related faults, and (3) the regional-scale influence of these inherited structures on the post-Paleozoic strain localization in the study area. Our 3D model shows that the pattern of Variscan shear zones that were developed at the end of the Paleozoic involved the whole crust, as emphasized by the Moho offsets. These shear zones were reactivated and localized Meso-Cenozoic deformation. The Variscan deformation pattern controlled the geometry of extensional basins, the propagation of Pyrenean-Provence deformation, and finally the Alpine deformation at crustal scale. Our 3D model shows minor crustal thickening (ca. 40 km) located below the Pelvoux External Crystalline Massif, which probably resulted from both Pyrenean and Alpine tectonic phases. In contrast, the southern part of the Alpine front shows a thinned crust (ca. 18 km) resulting from extensional Meso-Cenozoic phases between the Cévennes margin and the Durance basin.

塑造西南阿尔卑斯山前陆的地壳结构:三维地质建模的启示
再活化过程在变形定位中发挥着重要作用,但在岩石圈尺度上仍难以确定。在这项工作中,我们建立了一个三维结构模型,该模型能够弥合地表观测到的主要构造结构与从西阿尔卑斯山外部及其前陆获取的地球物理数据推断出的主要界面(莫霍洛维奇不连续面(以下简称莫霍面)和基底顶部)的几何形状之间的差距。这些构造结构的几何形状与其地球动力演化相关联。这项研究的主要结果突出显示了:(1) 厚皮比利牛斯-普罗旺斯和阿尔卑斯构造的强大作用,(2) 瓦里斯坎剪切带和相关断层的岩石圈根基,(3) 这些继承构造对研究区域后古生代应变定位的区域性影响。我们的三维模型显示,古生代末期形成的瓦里坎剪切带模式涉及整个地壳,莫霍偏移也强调了这一点。这些剪切带重新激活了中新生代的局部变形。Variscan变形模式控制了延伸盆地的几何形状、比利牛斯-普罗旺斯变形的传播,并最终控制了地壳尺度上的阿尔卑斯山变形。我们的三维模型显示,位于佩尔沃外结晶地块下方的地壳略有增厚(约 40 千米),这可能是比利牛斯和阿尔卑斯构造相共同作用的结果。与此相反,阿尔卑斯山前缘南部的地壳变薄(约 18 千米),这可能是塞文山脉边缘和杜纳尔河盆地之间的中新生代延伸阶段造成的。
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来源期刊
Tectonophysics
Tectonophysics 地学-地球化学与地球物理
CiteScore
4.90
自引率
6.90%
发文量
300
审稿时长
6 months
期刊介绍: The prime focus of Tectonophysics will be high-impact original research and reviews in the fields of kinematics, structure, composition, and dynamics of the solid arth at all scales. Tectonophysics particularly encourages submission of papers based on the integration of a multitude of geophysical, geological, geochemical, geodynamic, and geotectonic methods
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