LOCALISATION OF EROSIONAL DENUDATION DURING PYRENEAN OROGENESIS: IMPLICATIONS FOR FAULT DEVELOPMENT

The Pyrenees is an asymmetric, doubly-convergent orogen formed through Mesozoic-Cenozoic collision between the Afro-Iberian and European plates. Quantification of the uplift and denudation processes across the Pyrenean range provides constraints on the vertical component of its tectonic evolution and offers implications for sediment discharge toward the foreland.

Vertical profile AFT analysis from the westerly portion of the Maladeta massif (Fitzgerald et al. 1999) have indicated rapid (2-4mm/yr) exhumation between 36-32Ma. These ages correlate with the accumulation of thick alluvial conglomerates <15km to the south of the massif, onlapping the southern margin of the axial zone. The high exhumation gradient between the massif and the conglomerates is likely to be accommodated structurally within the Nogueres Zone. This region is characterised by several steep, southward-dipping faults that have been interpreted as thrust planes rotated in advance of a major antiformal stack.

U/Th-He analysis of apatites is applied to better understand the spatial distribution of uplift within the Axial Zone. Furthermore, stratigraphic analysis of growth stratal geometries in the dated synorogenic deposits combined with a detailed structural investigation of the underlying Nogueres thrust sheet is proposed to evaluate the mechanical accommodation of such localised gradients in exhumation and erosional denudation and, hence, better constrain tectonic models of Pyrenean evolution.