Sediment recycling in the South Pyrenean Foreland Basin: impact of grain size and source rock distribution on compositional signatures

Sedimentary provenance studies have long played a crucial role in elucidating source-to-sink processes across various tectonic settings throughout geological time. Foreland basins, in particular, record the erosional and exhumation history of their source areas, offering valuable insights into the chronology of deformation and the evolution of drainage areas. However, detrital signatures do not always fairly represent the composition of their drainage areas. Therefore, efforts are needed to better understand the factors controlling signal propagation from primary sources to ultimate sinks. The Jaca-Pamplona basin in the southern Pyrenees provides an excellent opportunity to explore the propagation and distribution of provenance signals in a setting with multiple source areas. We present combined data from detrital zircon U-Pb dating, sandstone petrography, and pebble point counting which allow us to infer the source area composition, its evolution, and the controls on provenance signal propagation. Our results indicate that alluvial fans had a source area composed of the North Pyrenean Zone and earlier, deep-marine synorogenic deposits, as evidenced by the overwhelming presence of recycled turbidite clasts. However, detrital zircon U-Pb age data from these alluvial fan deposits show a dominant Cadomian signature, while the turbidites exhibit a dominant Variscan signature, highlighting the complexity introduced by sediment recycling. We propose that the areal distribution of source rocks in the drainage area, transport distance, and differential weathering processes can explain this compositional effect. This is further supported by the clear grain-size dependence of the petrographic detrital modes, which show a positive correlation between grain size and the amount of recycled grains. Therefore, this study underscores the importance of integrating various provenance techniques to improve provenance reconstructions and to identify the intrinsic factors controlling the propagation and representativity of sediment sources.