No abstract

No abstract

No abstract

We investigate how sedimentary systems respond to tectonic uplift during the last stages of infilling of a foreland basin. Massive conglomeratic deposits characterize the last stage of basin fill in the Jaca basin, the western portion of the South Pyrenean foreland. We conduct detrital zircon U–Pb geochronology in a 3000 m thick Cenozoic section containing the transition from deltaic to alluvial environments with the aim of reconstructing changes of provenance in this key stage of evolution of the basin. The last conglomeratic deposits of the basin belong to the San Juan de la Peña alluvial fan, which has previously been assigned an early Oligocene age. Our results show the presence of earliest Miocene detrital zircons at the base of the fan. Zircon double-dating reveals identical U–Pb and (U–Th)/He ages, which is indicative of a volcanic origin for these zircons. We therefore conclude that this fan was deposited during early Miocene times. Our data establish a new chronological framework for deformation and sedimentation in the South Pyrenean foreland, with strong implications for the dynamics and palaeogeography governing the last episodes of basin fill. Our results support synchronous sedimentation in the Jaca piggy-back basin and in the autochthonous Ebro basin during the last stages of Pyrenean compression in the Miocene. This work emphasizes the tectonic controls on the configuration of the drainage basin and gives insights into the evolution of the drainage network in internally drained basins. Supplementary material: S1: Extended Zircon U-Pb LA-ICP-MS methodology. S2: Reduced detrital zircon U-Pb dataset for all analysis. S3: All age spectra. S4: zHe data. S5: Sample location for the analyzed samples are available at: https://doi.org/10.6084/m9.figshare.c.4507073

In the Jaca foreland basin (southern Pyrenees), two main sediment routing systems merge from the late Eocene to the early Miocene, providing an excellent example of interaction of different source areas with distinct petrographic signatures. An axially drained fluvial system, with its source area located in the eastern Central Pyrenees, is progressively replaced by a transverse-drained system that leads to the recycling of the older turbiditic foredeep. Aiming to provide new insights into the source-area evolution of the Jaca foreland basin, we provide new data on heavy-mineral suites, from the turbiditic underfilled stage to the youngest alluvial-fan systems of the Jaca basin, and integrate the heavy-mineral signatures with available sandstone petrography. Our results show a dominance of the ultrastable Ap-Zrn-Tur-Rt assemblage through the entire basin evolution. However, a late alluvial sedimentation stage brings an increase in other more unstable heavy minerals, pointing to specific source areas belonging to the Axial and the North Pyrenean Zone and providing new insights into the response of the heavy-mineral suites to sediment recycling. Furthermore, we assess the degree of diagenetic overprint vs. provenance signals and infer that the loss of unstable heavy minerals due intrastratal dissolution is negligible at least in the Peña Oroel and San Juan de la Peña sections. Finally, we provide new evidence to the idea that during the late Eocene the water divide of the transverse drainage system was located in the North Pyrenean Zone, and areas constituted by the Paleozoic basement were exposed in the west-Central Pyrenees at that time. Our findings provide new insights into the heavy-mineral response in recycled foreland basins adjacent to fold-and-thrust belts.