MULTI-MINERAL DETRITAL GEO- /THERMOCHRONOLOGY AND PECUBE THERMOKINEMATIC MODELING OF MODERN RIVER SANDS RECORD VARIABLE THERMAL HISTORIES ACROSS THE PYRENEES OROGEN

The Pyrenees Mountains are a classic example of a doubly-verging collisional orogenic system with flanking retro- and pro-foreland basin systems. This study integrates detrital zircon, rutile, and apatite U-Pb dating and, detrital zircon and apatite (U-Th)/He dating from modern river sands from the northern and southern Pyrenees, with PECUBE thermokinematic modeling of bedrock cooling ages to simulate detrital age distributions in order to evaluate: (1) regional patterns in long-term crustal processes associated with pre-Pyrenean crustal shortening, crustal thinning, and magmatism along the Iberian and European plate margin; (2) timing of regional cooling and inferred erosion related to Pyrenean orogenesis; and (3) the exhumation processes associated with post-orogenic decay and erosion. Modern river multi-mineral detrital geo-/thermochronometry results are consistent with previous bedrock thermal history models and records punctuated Variscan and Pyrenean orogens related cooling events in the pro-wedge. In contrasts, the retro-wedge sample preserve Ediacaran to Neogene ages that reflect a protracted thermo-tectonic evolution of the European and Iberian plate margins related to break-up and assembly of the Gondwana, Pangea, and Pyrenean-Alpine orogenic cycles. Detrital age distributions from PECUBE modeling predict the Pyrenean age component in both detrital apatite and zircon (U-Th)/He age distributions, indicating the modeled exhumation patterns in the Axial Zone and Northern Pyrenean Zone can predict observed Pyrenean thermochronology ages. This demonstrates that comparing observed data to modeled detrital age distributions from thermokinematic models can be used to understand the tectonic and surface processes recorded in detrital thermochronometric data in modern systems and over geologic timescales. The presence of strong Pyrenean age peaks among the modern river sand and modeled detrital cooling age distributions suggest retro-wedge deformation and exhumation remained active during the main phase of pro-wedge activity. Isolated Miocene apatite He ages from the North Pyrenees modern river record post-orogenic cooling, due to tectonic mode switch to extension and (or) climate driven enhanced exhumation.