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.

中文翻译：

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塑造西南高山前陆的地壳结构：3D 地质建模的见解


再激活过程在变形局部化中发挥着重要作用，但在岩石圈尺度上仍然难以确定。在这项工作中，我们建立了一个 3D 结构模型，该模型能够弥合在地表观察到的主要构造结构与从在西阿尔卑斯山外部及其前陆获取的地球物理数据。这些构造结构的几何形状是根据其地球动力学演化来解释的。这项研究的主要结果强调：（1）厚皮比利牛斯-普罗旺斯和阿尔卑斯构造的强烈贡献，（2）瓦里坎剪切带和相关断层的岩石圈根源，以及（3）这些的区域尺度影响遗传构造对研究区后古生代应变定位的影响。我们的 3D 模型显示，古生代末期形成的瓦里斯剪切带模式涉及整个地壳，正如莫霍面偏移所强调的那样。这些剪切带被重新激活并局部中新生代变形。瓦里坎变形模式控制了拉张盆地的几何形状、比利牛斯-普罗旺斯变形的传播，以及最终地壳尺度上的阿尔卑斯山变形。我们的 3D 模型显示，佩尔武外部结晶地块下方有轻微的地壳增厚（约 40 公里），这可能是比利牛斯和阿尔卑斯构造阶段的结果。相比之下，阿尔卑斯山前缘的南部显示出由于塞文山脉边缘和杜兰斯盆地之间的中新生代拉张而形成的地壳变薄（约18公里）。