Comparative Subsidence in the Aquitaine and Ebro Basins

P. Desegaulx, I. Moretti

The recent deep seismic profile across the Pyrenees has confirmed the flexure and deepening of the Iberian plate underneath the Pyrenean thrusts. Hence the Ebro basin may be considered as a foreland basin. The Cenozoic subsidence has been studied and compared to the plate flexure at simple convergent boundaries. A thin elastic sheet model is used to compute the lithospheric flexure at continental subduction zones. A regional model takes into account both lithospheric flexure and evolution of the sedimentary load. The gravity anomalies are computed for the present stage and compared to the available data. The study of subsidence during the Mesozoic allows us to estimate variations in the crustal thickness of the plates before the Pyrenean orogeny. Flexural studies emphasiz the influence of the north Iberic thrust in the southwestern part of the Ebro basin. The geometry of this basin may be explained by spatial boundary conditions. The ages of the first postorogenic deposits show the southward expansion of the basin. On the contrary, in the Aquitaine basin, the data show the northward expansion of Cenozoic deposits, in agreement with foreland modeling hypotheses.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.