Along-Strike Variation of the Uplift and Exhumation of the Pyrenean Orogen: Constraining the Evolution of an Intraplate Collisional Orogen

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The Pyrenean Mountains of Spain and France provide an excellent natural laboratory to study fundamental tectonic processes involved in the formation of intraplate orogenic systems. The Pyrnenean Orogen formed as a result of continent-continent convergence between the Iberian plate and the European Plate, beginning ~80 million years ago. In the central Pyrenees, shortening due to convergence was initially accommodated on relict extensional structures, formed prior to convergence, when the region was an extensional basin. When relict extensional structures could no longer accommodate shortening, deformation was taken up by movement on thrust faults that led to the formation of stacked antiformal nappes. Plate reconstructions and balanced cross-sections indicate deformation youngs to the west, the amount of convergence decreases to the west and the structure of the mountain range varies considerably. This project uses low to medium temperature thermochronologic methods to constrain the variation in the time-temperature history of rocks within the Pyrenean mountain belt. The across-strike (north-south trend) and along-strike (east-west trend) variation in the thermal, and denudation history of the orogen are being constrained using apatite fission track thermochronology, apatite Uranium-Thorium-Helium dating and Argon-Argon analysis of potassium feldspars on selected granite massifs from the central and western Pyrenees. The variation in the denudation history is being used to assess whether the onset of convergence/thrusting is synchronous or diachronous with uplift and erosion, whether denudation youngs to the west, if the amount of denudation decreases westward, and if the across-strike denudation pattern is symmetric or asymmetric along the range. These results are being used to quantify the four dimensional evolution of the Pyrenean continental collisional orogen and to evaluate processes associated with the formation of intraplate orogenic systems. The outcome of this research is of interest to a wide range of earth scientists who study orogenic systems, including thermochronologists, tectonicians, geodynamicists, reflection seismologists, sedimentologists and basin analysts. Funding provides research training and education for a postdoctoral research associate and undergraduate students. Field and lab based components of this project promote integration of research with teaching activities. Collaboration with Spanish colleagues enhances international scientific cooperation and educational training, by facilitating visits that include fieldwork, project discussions, and shared use of analytical facilities.