International audienceEstimating shortening in collision belts is critical to reconstruct past plate motions. Balanced cross-section techniques are efficient in external domains but lack resolution in the hinterland. The role and the original extent of the continental margins during the earliest stages of continental convergence are debated. Here we combine existing and new sequentially restored cross sections in the central Pyrenees, with Iberia/Europe (IB/EU) plate kinematic reconstructions and new apatite fission track, zircon (U-Th)/He, and U/Pb ages to discuss higher and lower bounds of crustal shortening and determine the amount of distal margin sutured during collision. We show that after extension in the Albian (~110 Ma), a 50 km wide extremely thinned crustal domain underwent subduction at 83 Ma. Low-temperature data and thermal modeling show that synorogenic cooling started at 75–70 Ma. This date marks the transition from suturing of the highly extended margin to collision of the more proximal margin and orogenic growth. We infer a relatively low crustal shortening of 90 km (30%) that reflects the dominant thick-skinned tectonic style of shortening in the Pyrenees, as expected for young (Mesozoic) and weak lithospheres. Our proposed reconstruction agrees with IB/EU kinematic models that consider initially rapid convergence of Iberia, reducing from circa 70 Ma onward. This study suggests that plate reconstructions are consistent with balanced cross sections if shortening predicted by age-dependent properties of the continental lithosphere is taken into account

15Earth-surface processes operate across erosionally dominated landscapes and 16 deliver sediment to depositional systems that can be preserved over a range of timescales. 17

This paper is an attempt to quantify the plausible time scales of clastic sediment supply variations at the entrance of sedimentary basins. Our approach is based on the sedimentary system concept, which simplifies natural systems by dividing them into three zones of dominant processes: the erosion, the transfer, and the sedimentation subsystems. We examine recent results from geomorphology, which show that frequent climate changes can induce high-frequency sediment flux variations at the outlet of the source area. We put forward the crucial role of the transfer subsystem, which conveys sediment from the erosion zone to the basin. By applying a diffusive model to a number of worldwide rivers, we extend from large (>1000 km) to intermediate (>300 km) rivers the previous finding that the transfer subsystem acts as a buffer for short periods sediment pulses (tens to hundreds of kiloyears). This implies that high-frequency stratigraphic cycles in clastic accumulations fed by large drainage systems are unlikely to reflect sediment supply cycles of tens to hundreds of thousands of years of periodicities. D