Abstract
Abstract Large thermochronologic data sets enable orogen-scale investigations into spatio-temporal patterns of erosion and deformation. We present the results of a thermo-kinematic modeling study that examines large-scale controls on spatio-temporal variations in exhumation as recorded by multiple low-temperature thermochronometers in the Pyrenees mountains (France/Spain). Using 264 compiled cooling ages spanning ∼200 km of the orogen, a recent model for its topographic evolution, and the thermo-kinematic modeling code Pecube, we evaluated two models for Axial Zone (AZ) exhumation: (1) thrust sheet–controlled (north-south) exhumation, and (2) along-strike (east-west) variable exhumation. We also measured the degree to which spatially variable post-orogenic erosion influenced the cooling ages. We found the best fit for a model of along-strike variable exhumation. In the eastern AZ, rock uplift rates peak at ≥1 mm/yr between 40 and 30 Ma, whereas in the western AZ, they peak between 30 and 20 Ma. The amount of post-orogenic (<20 Ma) erosion increases from <1.0 km in the eastern Pyrenees to >2.5 km in the west. The data reveal a pattern of exhumation that is primarily controlled by structural inheritance, with ancillary patterns reflecting growth and erosion of the antiformal stack and post-orogenic surface processes.
Highlights
The feedback between tectonically driven rock trajectories and erosion controls orogenic topography, generates exhumation, and integrates crustal deformation, lithology, surface processes, mantle dynamics, and climate (e.g., Whipple, 2009; Jamieson and Beaumont, 2013)
Thermochronology is the prime tool for quantifying exhumation and, when paired with independent constraints on topography, can provide valuable information for investigating these relationships
Our results show that spatio-temporal patterns of exhumation are controlled by structural inheritance and post-orogenic surface processes, and to a limited extent, by thrust-sheet kinematics
Summary
The feedback between tectonically driven rock trajectories and erosion controls orogenic topography, generates exhumation, and integrates crustal deformation, lithology, surface processes, mantle dynamics, and climate (e.g., Whipple, 2009; Jamieson and Beaumont, 2013). We evaluated our models using 264 compiled thermochronologic ages, including apatite (U-Th)/He (AHe, n = 77), apatite fissiontrack (AFT, n = 123), zircon (U-Th)/He (ZHe, n = 40), and zircon fission-track (ZFT, n = 24) data (Fig. 2) (Morris et al, 1998; Fitzgerald et al, 1999; Sinclair et al, 2005; Gibson et al, 2007; Jolivet et al, 2007; Maurel et al, 2008; Gunnell et al, 2009; Metcalf et al, 2009; Herman et al, 2013; Bosch et al, 2016; Vacherat et al, 2016; Fillon et al, 2020) These data collectively record rock cooling from ∼300 to ∼60 °C and encompass the pre-, syn-, and postorogenic periods.
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