Exhumation of the southern Pyrenean fold-thrust belt from orogenic growth to decay

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Rushlow, Caitlin
- Affiliation: College of Arts and Sciences, Department of Geological Sciences

Abstract

We quantify the spatiotemporal patterns of exhumation across the southern fold-thrust belt (FTB) margin with apatite fission track (AFT) thermochronology and compare the results with existing deformation, exhumation, and sedimentation chronologies. Eighteen bedrock samples record exhumation ~90 to 10 Ma. Rocks from the range core (Axial Zone) record rapid exhumation that progresses east to west and north to south consistent with patterns of tectonically-driven uplift. Sediments shed into piggyback basins retain a detrital exhumation signal. Samples from other FTB structures record in situ exhumation, suggesting sedimentary burial of sufficient magnitudes to reset the AFT system. A major exhumation phase occurs at the boundary between the thick- and thin-skinned portions of the FTB wedge at 25-20 Ma. We suggest that this exhumation records uplift from sediment overloading the outboard FTB structures and/or wetter climate conditions. A final exhumation phase between ~20-10 Ma may be a response to base level lowering.

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