Salt tectonics in the Central Southern Pyrenees: Integrated tectonostratigraphic and numerical modelling study
Antonio TEIXELL – Universitat Autonoma de Barcelona
The Montsec FTB is re-interpreted in terms of halokinesis : developed since Cretaceous rifting, salt ridges (Montsec Ridge) and mini-basins evolved into buckle folds during the Pyrenean compression, for which the imbrication and thrusting sequences relate to primary welding of the basal evaporite.
With the onset of Pyrenean compression the driving mechanisms for folding shifted from predominantly halokinesis, to predominant compressional buckling. The Oligocene imbrication of synclines may obey to primary welding of the basal evaporite layer and/or erosion/unroofing of salt anticlines and diapirs.
The migrating load of the Paleogene intramontane alluvial systems on salt caused progressive northward tilting and migration, enabled by the expulsion of salt at Senterada.
Erosion determines the timing of salt anticline/diapir unroofing, and therefore the transition from buckle folding, when the sedimentary cover is connected, to load-dominated subsidence.
Drop shaped synclines form at preexisting diapir flanks (e.g. Àger basin vs Montsec sait wall) was favoured by salt evacuation and sediment loading.
Field mapping, clast source statistics and numerical modeling were used to support these interpretations.