Syntectonic sedimentation controls on the evolution of the southern Pyrenean fold-and-thrust belt: Inferences from coupled tectonic-surface processes models

Numerous studies in the Central Pyrenees have provided evidence for a rapid phase of exhumation of this mountain belt during the Late Eocene (37-30Ma). Simultaneously, the closure of the Ebro foreland basin allowed the accumulation of sediments at the southern Piedmont, which partially covered the fold-and-thrust belt from Late Eocene (e.g., when it was still actively deforming) to Miocene times. We aim here at understanding the consequences of such syntectonic sedimentation on the Southern Pyrenean fold-and-thrust belt by using a 2-D numerical model that reproduces the development of a thin-skinned wedge subject to different modes of sedimentation and erosion. The results show contrasting fold-and-thrust belt behavior when applying aggrading or prograding sedimentation, which we link to the critical state of the wedge. When the sediments are sourced from the hinterland (progradation), the thrusting propagates toward the foreland; whereas when the sediments aggrade from the basin, the thrusting sequence migrates backward. This latter mode shows patterns of deformation that compare favorably to the Pyrenean thrusting sequence observed during Eocene-Miocene times.