The Pyrenean Belt ends against the Gulf of Lion passive margin. The mechanism responsible for dismantling the mountain belt during Oligocene rifting has not yet found a proper explanation. The Late Eocene and Oligocene period is characterized by a first order change in subduction dynamics in the Mediterranean and the subduction zones started to retreat with back-arc basins forming at the expense of mountain belts build earlier. The slab subducting below Provence and Sardinia-Corsica started a fast south-eastward retreat, forming the Liguro-Provencal Basin. This syn-rift period in the Gulf of Lion margin is coeval with exhumation of the eastern Pyrenean basement, while underthrusting of Iberia continued until Early Miocene. Based on interpretation of seismic lines, we propose a tentative model in which the mantle flow related with Apennine slab retreat has (1) exhumed and thinned the continental mantle below the Gulf of Lion and the eastern Pyrenees and (2) exhumed the lower crust, leading to crustal thinning and subsidence of the Gulf of Lion margin. The wide distribution of syn-rift volcanism in the transition between the Gulf of Lion and Valencia Basin is in line with the geometry observed in the margin suggesting ductile deformation of a weak continental crust, typical of volcanic margins. The direction of SKS-waves seismic anisotropy below the Pyrenees and the observed migration of exhumation toward the west fit this simple model. The concentration of syn-rift magmatism and the ductile behaviour of the crust during rifting can be explained by the high heat flow above the slab tear that separates the future Apennines and Maghreb branches of the West Mediterranean subduction zone. Finally, removal of upper mantle, inducing uplift and an increase of potential energy, may explain why thrusting continued in the Pyrenees while rifting was still active nearby along strike.

中文翻译：

---

地幔流对山带的快速拆除：比利牛斯山脉和利古罗-普罗旺斯裂谷的晚造山演化

比利牛斯带终止于狮子湾被动边缘。在渐新世裂谷期间负责拆除山带的机制尚未找到适当的解释。晚始新世和渐新世时期的特点是地中海俯冲动力学发生一级变化，俯冲带开始后退，弧后盆地形成，但以山带较早构建为代价。俯冲到普罗旺斯和撒丁岛-科西嘉岛下方的板块开始快速向东南撤退，形成利古罗-普罗旺斯盆地。狮子湾边缘的这个同裂谷时期与东比利牛斯基底的挖掘同时期，而伊比利亚的下冲作用一直持续到早中新世。根据地震测线的解释，我们提出了一个暂定模型，其中与亚平宁板块后退相关的地幔流已经（1）挖掘和减薄狮子湾和东比利牛斯山脉下方的大陆地幔和（2）挖掘下地壳，导致地壳变薄和下沉狮湾缘。狮子湾和瓦伦西亚盆地之间过渡区的同裂谷火山活动的广泛分布与在边缘观察到的几何形状一致，表明弱大陆地壳的韧性变形，典型的火山边缘。比利牛斯山脉下方的 SKS 波地震各向异性方向和观测到的挖掘物向西迁移符合这个简单的模型。裂谷期间同裂谷岩浆活动的集中和地壳的韧性行为可以用板块撕裂上方的高热流来解释，板块撕裂将未来的亚平宁山脉和西地中海俯冲带的马格里布分支分开。最后，上地幔的移除，引起隆起和势能的增加，可以解释为什么在比利牛斯山脉继续推进，而在附近沿走向仍然活跃的裂谷。