Quantifying deformation processes in the SE Pyrenees using U–Pb dating of fracture-filling calcites

A significant challenge in brittle fold and thrust belts analysis is to quantify the timing of the deformation processes, since suitable minerals for dating and well-preserved growth strata sediments are scarce or absent. Here, we quantify the duration of thrust sheet emplacement and shortening rates in the SE Pyrenean thrust sequence using U-Pb dating of fracture-filling calcites. The obtained U-Pb dates reveal a minimum duration for the emplacement of each thrust unit (18.7 Ma for the Boixols-Upper Pedraforca, 11.6 Ma for the Lower Pedraforca and 14.3 Ma for the Cadi), and that piggy-back thrusting was accompanied by post-emplacement deformation of upper thrust sheets above lower ones during their south-directed tectonic transport. Shortening rates of 0.6 mm/yr, 3.1 mm/yr and 1.1 mm/yr from older to younger emplaced thrust sheets were calculated. The results also reveal the formation of local normal faults during the late Oligocene as a result of the late stages of compression and exhumation in the SE Pyrenees. Finally, we observed that temperatures higher than 110 °C could be a limiting factor when applying the U-Pb dating method. Supplementary material:https://doi.org/10.6084/m9.figshare.c.5078862