During its late‐stage evolution, the European Alpine orogen witnessed a northwest‐directed propagation of its deformation front along an evaporitic basal décollement into the foreland. This resulted in the decoupling of the northern Alpine Molasse Basin from its basement and the formation of the Jura fold‐and‐thrust belt. Here, we present the first absolute age and temperature constraints on deformation along this basal décollement using carbonate U‐Pb LA‐ICP‐MS dating and clumped isotope thermometry. We analyzed calcite veins associated with a thrust fault branching off from the basal décollement in the distal Molasse Basin and slickenfibers from thrusts and strike‐slip faults in the eastern Jura Mountains. Our U‐Pb data provide evidence for tectonic activity related to Alpine contraction between 14.3 and 4.5 Ma ago. According to the oldest deformation ages, the propagation of Alpine deformation into the distal foreland along the basal décollement occurred earlier than previously inferred by biostratigraphy, at Middle Miocene (Langhian) times at the latest. Younger deformation ages between 11.3 and 4.5 Ma correspond very well in time with shortening in the Subalpine Molasse and the Central Alps, proving simultaneous tectonic activity along both thrust fronts; i.e., the Jura Mountains and the Subalpine Molasse. Clumped isotopes reveal vein calcite precipitation at temperatures between 53 and 104 °C from fluids with oxygen isotope compositions between −6.2‰ and +9.5‰ reflecting distinct burial settings. Combined, our U‐Pb and clumped isotope data show that the burial conditions in the studied area remained constant between 14.3 and 4.5 Ma indicating that large‐scale foreland erosion did not initiate before 4.5 Ma.

中文翻译：

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碳酸盐U-Pb定年和成簇同位素对侏罗折叠冲断带基底断面变形的绝对年龄和温度约束

在其晚期演化过程中，欧洲高山造山带目睹了它的形变锋面沿着蒸发基底基底层向西北方向传播到前陆。这导致了北部高山莫拉西盆地与它的基底解耦，并形成了侏罗褶皱-冲断带。在这里，我们使用碳酸盐U-Pb LA-ICP-MS测年法和成簇同位素测温法介绍了沿该基底弯折变形的第一个绝对年龄和温度约束。我们分析了与从莫拉西盆地远端的基底支流分支出来的逆冲断层相关的方解石脉，以及侏罗山东部的逆冲断层和走滑断层的光滑纤维。我们的U-Pb数据提供了与14.3至4.5 Ma以前的高山收缩有关的构造活动的证据。根据最古老的变形年龄，高山变形沿基底扇形向远端前陆的传播发生的时间要比以前通过生物地层学推断的时间要早​​，最晚是中新世中期（Langhian）。在11.3至4.5 Ma之间的年轻变形年龄与亚高山Molasse和中部阿尔卑斯山的缩短时间在时间​​上非常吻合，证明了在两个逆冲锋面都同时发生了构造活动。即侏罗山和亚高山山脉莫拉塞。聚集的同位素揭示了温度在53至104°C之间的方解石沉淀，其流体的氧同位素组成在-6.2‰至+ 9.5‰之间，反映了不同的埋葬环境。结合我们的U-Pb和成簇的同位素数据表明，研究区域的埋葬条件在14.3和4之间保持恒定。