Abstract The Bay of Biscay-Pyrenean rift system is a world-class example of an inverted hyperextended rift. However, tectonic questions such as the linkage of the extensional system, the magnitude of crustal extension, the interpretation of the syn-rift sequences and the amount of shortening during tectonic inversion remain controversial. This paper presents a sequentially restored crustal-scale transect across a key sector of the central Basque-Cantabrian Basin, which allows the prevailing tectonic models to be evaluated. Two separated phases of rifting during Permo-Triassic and late Jurassic-Early Cretaceous times led to breakup. In the second phase, a southerly-dipping extensional detachment accommodated at least 28 km of horizontal extension while separating the Iberian and European plates, and exhuming mantle rocks in the footwall. The locus of volcanism migrated to the north, peaking during the hyperextension and post-rift stages. Mantle sources were influenced by deep OIB-type components most likely triggered by the ascending asthenospheric mantle. Therefore, gravitational forces linked to asthenospheric doming are interpreted as the primary driving mechanism during the peak strain rate. Evacuation of Upper Triassic salt during the syn-rift and post-rift stages determined the development of a salt-floored ramp-syncline basin next to the lower detachment ramp, and the sinking of minibasins in other areas. About 41 km of Cenozoic shortening (21%) were resolved by underthrusting of the crust beneath the shallow lithospheric mantle, leading to the formation of thrusts with opposite vergences at the distal basin boundaries, and by the reactivation of the extensional detachment as a thrust fault. The buttress of the overburden over the salt in the hyperextended domain created outstanding examples of squeezed diapirs, chevron folds and thrust splays. Our results have implications for a better understanding of the connection between the Atlantic Ocean and the Western Tethys along the Bay of Biscay-Pyrenean realm, the processes of crust denudation prior to breakup, and the incorporation of rifted domains into collisional orogens.

中文翻译：

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Getxo 地壳尺度横截面：测试比斯开湾-比利牛斯裂谷系统的构造模型

摘要 比斯开湾-比利牛斯裂谷系统是世界级的倒超伸展裂谷实例。然而，伸展系统的联系、地壳伸展的幅度、同裂谷层序的解释以及构造反转过程中的缩短量等构造问题仍然存在争议。本文介绍了巴斯克 - 坎塔布连盆地中部的一个关键部分的顺序恢复的地壳尺度横断面，它允许对流行的构造模型进行评估。二叠纪-三叠纪和晚侏罗纪-早白垩世的两个分离的裂谷阶段导致破裂。在第二阶段，一个向南倾斜的伸展拆离容纳了至少 28 公里的水平伸展，同时分隔了伊比利亚和欧洲板块，并在下盘挖掘出地幔岩石。火山活动的轨迹向北迁移，在超伸展和裂谷后阶段达到顶峰。地幔源受深部 OIB 型成分的影响，最有可能由上升的软流圈地幔触发。因此，与软流圈拱起相关的重力被解释为峰值应变率期间的主要驱动机制。同裂谷和后裂谷阶段上三叠统盐分的撤离决定了下拆离斜坡旁的盐底斜坡向斜盆地的发育，以及其他地区的小型盆地的下沉。大约 41 公里的新生代缩短（21%）被浅层岩石圈地幔下地壳的下冲作用解决，导致在盆地远端边界形成具有相反辐合度的逆冲冲断层，并且通过作为逆冲断层的伸展脱离的重新激活。超伸展区域盐上覆土的支撑创造了挤压底辟、人字形褶皱和逆冲张开的杰出例子。我们的研究结果对更好地理解大西洋和西特提斯沿比斯开湾-比利牛斯山脉之间的联系、破裂前地壳剥蚀的过程以及裂谷域与碰撞造山带的结合具有重要意义。