Postorogenic planar paleosurfaces of the central Pyrenees: weathering and neotectonic records

Bernard Monod (1) , Vincent Regard (2) , Julie Carcone (2) , Robert Wyns (1) , Frédéric Christophoul (2)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 GET - Géosciences Environnement Toulouse

Flat high-elevation surfaces in the Pyrenees are defined by thick weathered horizons that were developed from granitic lithology. We analysed such horizons in detail within two areas: the Bordères-Louron granite and the Aston massif. They are characterized by a lower fissured zone overlain by unconsolidated saprolite. Mapping these horizons allows a 3D reconstruction of the ancient paleosurface with an elevation uncertainty of 50 m. We discuss the age of weathering by means of stratigraphy and low-temperature thermochronology. The surfaces are clearly postorogenic, postdating Eocene-Oligocene denudation. Their incision and the fact they are stepped suggest (1) an increase of the local relief and (2) recent normal faulting.

Mots clés: Paleosurfaces; Weathering; Pyrenees; Postorogenic

Domaines: Géomorphologie; Tectonique; Pétrographie

Bernard Monod, Vincent Regard, Julie Carcone, Robert Wyns, Frédéric Christophoul. Postorogenic planar paleosurfaces of the central Pyrenees: weathering and neotectonic records. Comptes Rendus Géoscience, 2016, 348 (3-4), pp.184-193. ⟨10.1016/j.crte.2015.09.005⟩. ⟨hal-01212752⟩