In NW Europe, the late Carboniferous Variscan collision between the Laurussia and the Armorica-Gondwana continental blocks led to the development of a crustal-scale north-verging thrust system along the southern Laurussian margin. In northern France, the 3-D geometry and kinematics of the Variscan deformation front have been investigated on the basis of reprocessing and interpreting 532 km of industry-level seismic reflection profiles. This extensive seismic imaging provides new constraints on the structural and kinematic features of the orogenic front. It particularly emphasizes the localization of displacement along the main frontal thrust zone that accommodated more than 50 km of total displacement of the allochthonous units above the foreland. It also highlights the induced large underthrusting of the foreland basin below the frontal thrust zone, and its truncation in a general out-of-sequence mode of thrust propagation. We built structural maps that led to better delineating a major NW-SE lateral ramp along the main frontal thrust. The Mid-Upper Devonian series within the flexured foreland were deformed at depth by N060–080° trending and N110–130° trending syn-sedimentary normal faults that led to their south-to southwestward thickening. These pre-existing structures along the margin have exerted a primary control on the ensuing dynamics and geometry of the Northern Variscan Front by localizing both the frontal and lateral ramps during thrust wedge growth.

中文翻译：

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法国北部 Variscan 逆冲推力锋的 3-D 结构：来自地震反射剖面的新见解

在欧洲西北部，Laurussia 和 Armorica-Gondwana 大陆块之间的晚石炭纪 Variscan 碰撞导致沿 Laurussian 南部边缘的地壳尺度北向逆冲推力系统的发展。在法国北部，在对 532 公里工业级地震反射剖面进行再处理和解释的基础上，研究了 Variscan 变形前缘的 3D 几何和运动学。这种广泛的地震成像为造山带的结构和运动学特征提供了新的限制。它特别强调了沿主锋逆冲带的位移定位，该逆冲带容纳了前陆上方外来单元总位移超过 50 公里。它还突出了锋面逆冲带下方前陆盆地的诱导大逆冲，以及它在逆冲传播的一般无序模式中的截断。我们构建了结构图，从而更好地描绘了沿主要正面推力的主要 NW-SE 横向斜坡。弯曲前陆中上泥盆统系列在深部受到 N060-080°和 N110-130°走向的同沉积正断层的变形，导致其南向西南方向增厚。这些沿边缘预先存在的结构通过在逆冲楔生长过程中定位锋面和横向坡道，对北瓦里斯坎锋的后续动力学和几何形状施加了主要控制。我们构建了结构图，从而更好地描绘了沿主要正面推力的主要 NW-SE 横向斜坡。弯曲前陆中上泥盆统系列在深部受到 N060-080°和 N110-130°走向的同沉积正断层的变形，导致其南向西南方向增厚。这些沿边缘预先存在的结构通过在逆冲楔生长过程中定位锋面和横向坡道，对北瓦里斯坎锋的后续动力学和几何形状施加了主要控制。我们构建了结构图，从而更好地描绘了沿主要正面推力的主要 NW-SE 横向斜坡。弯曲前陆中上泥盆统系列在深部受到 N060-080°和 N110-130°走向的同沉积正断层的变形，导致其南向西南方向增厚。这些沿边缘预先存在的结构通过在逆冲楔生长过程中定位锋面和横向坡道，对北瓦里斯坎锋的后续动力学和几何形状施加了主要控制。