Quantified vertical motions and tectonic evolution of the SE Pyrenean foreland basin

Abstract Local isostatic backstripping analysis is performed across the eastern part of the Ebro foreland basin between the Pyrenees and the Catalan Coastal Ranges. The subsidence analysis is based on two well-dated field-based sections and four oil-wells aligned parallel to the tectonic transport direction of the eastern Pyrenean orogen. The marine infill of the foreland basin is separated into four, third-order, transgressive-regressive depositional cycles. The first and second depositional cycles are located in the Ripoll piggy-back basin and the third and fourth ones are located south of the syn-depositional emergent Vall-fogona thrust. Subsidence curves display a typical convex-up shape with inflection points recording the onset of rapid tectonic subsidence. Inflection points coincide roughly with the base of depositional cycles. Rates of tectonic subsidence are less than 0.1 mm a −1 in distal parts of the basin and up to 0.53 mm a −1 in proximal parts during second depositional cycle. Younger depositional cycles show maximum rates of tectonic subsidence of 0.26 mm a −1 . The locus of subsidence within the basin migrated southward at a rate of c . 10 mm a −1 . This flexural wave crossed the complete Ebro foreland basin in 10–11 Ma. The intraplate Catalan Coastal Ranges at the southeastern margin of the Ebro foreland basin produced an increase of tectonic subsidence rate at 41.5 Ma. Maximum rates of tectonic subsidence coincide with deep-marine infill of the basin, maximum rates of shortening and thrust front advance, and low topographic relief orogenic wedge. Transgressive-regressive depositional cycles can be controlled partly by reductions of available space within the basin during tectonic thickening of the sedimentary pile by layer parallel shortening, folding and thrusting. Although much less constrained, an approximation of post-thrusting exhumation and isostatic and tectonic uplift, as well as a first determination of possible amounts of eroded material of parts of the Ebro basin illustrate the impact of post-depositional erosion and uplift on the foreland.