HEAT-FLUX AND TIMING OF THE DRIFTING STAGE IN THE LIGURIAN-PROVENCAL BASIN (NORTHWESTERN MEDITERRANEAN)

The surface thermal flux in the Ligurian-Provencal basin is accounted for by a three-component model for the continental margins and a cooli ng model for the oceanic domain. In the continental margins the surfac e heat-flux data,corrected for the main perturbations, range from 65-7 0 to 85-90 mW m(-2); the background heat flowing out from the asthenos phere is 38 mW m(-2). Heat-flux data from the oceanic domain indicate that the drifting stage should have begun 4-5 Ma earlier and ended 2-3 Ma later than previously inferred, being consistent with recent paleo magnetic results. A decoupling of Corsica from Sardinia during driftin g is also validated by the different periods of oceanic accretion whic h, in the northern sector, seems to be shorter. The rift stage tarted in the Oligocene and ended about 27 Ma ago between Sardinia and the Gu lf of Lion. The rotation of Corsica and Sardinia, which was accompanie d by westward crustal accretion, ended about 17 Ma ago. Such a wider t ime span for drifting involves a more tellable average spreading rate of 2.5 cm a(-1). An outline of the development of the basin during eac h evolutionary stage is drawn.