Exhumation of the Pyrenean orogen: implications for sediment discharge

Abstract

Apatite fission track analyses of 21 samples from the central and eastern Pyrenees are modelled to generate time-temperature plots for the post 110±10°C cooling history over the 40-10 Ma time interval. Modelled thermal histories have been converted into exhumation plots through the application of the present-day geothermal gradient in the Pyrenees. The documented geology of the Pyrenees allows us to assume no significant extensional unroofing and subvertical exhumation trajectories, thus enabling exhumation to be translated into erosional denudation. Maps of denudation have been constructed for six, 5-Myr time intervals. Denudation varied with a 20-50-km length scale, and does not appear to have been related to the major structural zones of the mountain belt. Spatially averaged denudation rates for the six time intervals ranged from 34 to 61 mm kyr −1 assuming the present-day geothermal gradient. Maximum rates of 240 mm kyr −1 occurred in the interval 35-30 Ma, in the region of the Querigut-Millas massif.Assuming the denudation resulted primarily from erosion, the denudation maps can be used to calculate sediment discharge through time to the neighbouring foreland basins. Using a series of rectangular drainage basins with a 251 aspect ratio (based on modern linear mountain belts) and a location of the main drainage divide based on the mean present-day position, it is possible to evaluate the potential for spatial and temporal variations in sediment discharge as a function of denudation. The results show along-strike variations in sediment discharge between drainage basins of 500%, and temporal variations from individual basins of >300%. A comparison of total sediment discharge per year to the Ebro and Aquitaine basins, assuming a fixed drainage divide, shows that the discharge to the south is likely to have been between 1.5 and 2.8 times greater than to the north. sediment supply derived from erosion of the mountain

The Meso-Cenozoic thermo-tectonic evolution of the Eastern Pyrenees: an 40Ar/39Ar fission track and (U–Th)/He thermochronological study of the Canigou and Mont-Louis massifs

“…The preservation of a core-rim age zoning in biotite, similar to that observed in muscovite, confirms the fact that the step-heating procedure tends to average the isotopic gradients (Lo et al 2000) resulting from slow cooling (Hodges and Bowring 1995) or thermal overprinting (Hames and Cheney 1997). Given the present geological context, thermal overprinting in Alpine (Morris et al 1998;Sère 1993). Dashed grey and black lines represent calculated exhumation rates from AFT and AHe ages, respectively time is the most probable process responsible for argon loss in the samples.…”

Thermochronology constraints for the propagation sequence of the south Pyrenean basement thrust system (France‐Spain)

“…The Axial Zone and the south Pyrenean foreland basin form a typical accretionary prism with a southward vergence. Its general tectonic structure and the tectonic‐sedimentation relationships inside the foreland basin are well known [e.g., Séguret , 1972; Labaume et al , 1985; Muñoz , 1992; Teixell , 1996; Teixell and Muñoz , 2000; Millán Garrido et al , 2000; Vergés et al , 2002], but only a few geochronological data are available to constrain the evolution of the prism, mostly in the central part of the Axial Zone [ Morris et al , 1998; Fitzgerald et al , 1999; Maurel , 2003; Sinclair et al , 2005].…”

Increase in late Neogene denudation of the European Alps confirmed by analysis of a fission-track thermochronology database

“…The spatial integration of discrete thermochronological data covering large study areas is most easily achieved by interpolating between ages in map view (e.g., Hunziker et al, 1992; Morris et al, 1998;Schlunegger and Willet, 1999;Stephenson et al, 2006). Despite many years of intensive thermochronological studies in the Alps, samples permitting such analyses are still relatively rare, disallowing such a study at the orogen scale.…”