Abstract. Normal incidence seismic data provide the best images of the crust and lithosphere. When properly designed and continuous, these sections greatly contribute to understanding the geometry of orogens and, together with surface geology, to unravel their evolution. In this paper we present an almost complete transect of the Iberian Massif, the westernmost exposure of the European Variscides. Despite the heterogeneity of the dataset, acquired during the last 30 years, the images resulting from reprocessing with a homogeneous workflow allow us to clearly define the crustal thickness and its internal architecture. The Iberian Massif crust, formed by the amalgamation of continental pieces belonging to Gondwana and Laurussia (Avalonian margin) is well structured in upper and lower crust. A conspicuous mid-crustal discontinuity is clearly defined by the top of the reflective lower crust and by the asymptotic geometry of reflections that merge into it, suggesting that it has often acted as a detachment. The geometry and position of this discontinuity can give us insights on the evolution of the orogen, i.e. of the effects and extent of the late Variscan gravitational collapse. Also, its position and the limited thickness of the lower crust in central and NW Iberia constraints the response of the Iberian microplate to Alpine shortening. This discontinuity is here observed as an orogeny-scale feature with characteristics compatible with those of the worldwide, Conrad discontinuity.

中文翻译：

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从地壳厚度和中地壳（康拉德）间断的几何结构推断伊比利亚地块的演化

摘要。正入射地震数据提供了地壳和岩石圈的最佳图像。如果设计合理且连续，这些部分将极大地有助于了解造山带的几何形状，并与地表地质一起阐明其演化。在本文中，我们介绍了伊比利亚断层的几乎完整的样带，这是欧洲Variscides的最西端。尽管在过去30年中获得了数据集的异质性，但使用均质工作流程进行再处理后得到的图像使我们能够清楚地定义地壳厚度及其内部结构。由冈瓦纳和月桂属（阿瓦隆边缘）的大陆块合并而成的伊比利亚地块地壳在上下地壳中结构良好。明显的中地壳间断是由反射性下地壳的顶部和合并到其中的反射的渐近几何形状清楚地定义的，这表明它经常起着分离作用。这种不连续的几何形状和位置可以使我们了解造山带的演化，即晚期瓦里斯卡因重力塌陷的影响和程度。同样，其位置以及中部和西北伊比利亚地区下地壳的有限厚度也限制了伊比利亚微孔板对高山缩短的响应。这种不连续性在这里被视为造山带尺度的特征，其特征与世界范围内的康拉德不连续性兼容。这种不连续的几何形状和位置可以使我们了解造山带的演化，即晚期瓦里斯卡因重力塌陷的影响和程度。同样，其位置以及中部和西北伊比利亚地区下地壳的有限厚度也限制了伊比利亚微孔板对高山缩短的响应。这种不连续性在这里被视为造山带尺度的特征，其特征与世界范围内的康拉德不连续性兼容。这种不连续的几何形状和位置可以使我们了解造山带的演化，即晚期瓦里斯卡因重力塌陷的影响和程度。同样，其位置以及中部和西北伊比利亚地区下地壳的有限厚度也限制了伊比利亚微孔板对高山缩短的响应。这种不连续性在这里被视为造山带尺度的特征，其特征与世界范围内的康拉德不连续性兼容。