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

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[1] This article presents (U-Th)/He thermochronological data from the Longmen Shan belt, eastern Tibet. Located between the Songpan-Garze terrane and the Yangtze craton, this mountain range is one of the steepest margins of the Tibetan Plateau and an important area for the comprehension of the mechanisms that control the dynamics of such plateau borders in terms of spatial distribution of deformation or timing of topographic building. We describe several age-elevation transects and perform forward modeling of our data to derive quantitative information on the exhumation of the range. A major phase of exhumation started at 8-11 Ma, with an average rate of $0.65 mm a À1

Fission-track (FT) analysis of detrital zircon from synorogenic sediment is a well established tool to examine the cooling and exhumation history of convergent mountain belts, but has so far not been used to determine the long-term evolution of the central Himalaya. This study presents FT analysis of detrital zircon from 22 sandstone and modern sediment samples that were collected along three stratigraphic sections within the Miocene to Pliocene Siwalik Group, and from modern rivers, in western and central Nepal