Salt tectonics in the Central Southern Pyrenees: Integrated tectonostratigraphic and numerical modelling study

Antonio TEIXELL – Universitat Autonoma de Barcelona

Major Results

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.


The role of Keuper in driving salt tectonics is explored during rifting and inversion in the Montsec area, and how it affects source and sediment dispersion pattern in a foreland basin context. Differential sedimentary loading and erosion during compression in turn is seen to relate to salt migration and associated folding:
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.


The erosion of the Nogueres thrust sheet in the Axial Zone enabled the sinking of the detached leading edge into the salt and the formation of the Senterada E-W trough, with alluvial conglomerates directly subsiding on top of salt. The compressional deformation front quickly reached the frontal domain (applicable to Serres Marginals early folding). Thick salt/overburden ratio and thick overburden favour broad inflation, inhibiting buckle fold nucleation and preventing the formation of smaller-wavelength folds.
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.