Recycling effects in detrital zircon U[sbnd]Pb signatures in a foreland basin: Identifying the multicyclic sediment sources of the Eocene-Miocene Jaca basin (southern Pyrenees, Spain)

Abstract

This work deals with the provenance evolution of the mid Eocene to early Miocene clastic deposits of the Jaca basin (southern Pyrenees), which record a main drainage network reorganization during the progressive tectonic uplift of the Pyrenean orogen. We present new detrital zircon UPb data which show a Variscan-dominated detrital zircon signature for the Lutetian Hecho Group turbidites, while the overlying late Eocene to early Miocene alluvial fan sediments record a Cadomian-dominated detrital zircon signature, allowing to document a major change in the source area. Moreover, a tectono-stratigraphic cyclicity can be identified in each of the turbidite systems that conform the upper Hecho Group, featuring an enrichment of the Variscan detrital zircon signal at the base of the system, which can be interpreted as the result of an efficient sediment transfer from distant Axial Zone sources during relative sea-level lowstands, while a dilution of this signal occurs during highstands, at the top of each system, due to the reduced erosion capability of the fluvial network. Integration of detrital zircon UPb data with sandstone petrography allows for improved resolution of the source-area shifts, for discrimination between first-cycle and multi-cycle zircons, and to identify that the detrital zircon signal of the alluvial fans does not fully represent the source area configuration. This study illustrates the importance of combining petrography with detrital zircon UPb data to improve provenance reconstructions and to identify the role of sediment recycling during progressive foreland evolution.