LONG-LISTENING MULTICHANNEL SEISMIC PROFILES IN THE VALENCIA TROUGH (VALSIS-2) AND THE GULF OF LIONS (ECORS) - A COMPARISON

The long listening Multichannel Seismic (MCS) profiles recorded during the Valsis and ECORS experiments were analysed in order to understand the rifting processes of a young passive margin. The seismic lines were interpreted within a geological framework which is considerably improved by the results from industrial wells. The distributed upper crust off Catalonia is tentatively connected with a Variscan front. The origin of lamellae in the lower crust beneath the Valencia shelf is discussed: a Variscan origin is rejected and a relation to a Jurassic extensional event is proposed. A companion basin to the onshore Maestrazgo basin is located off-shore of Valencia and these two basins are probably connected by the left-lateral strike-slip Castellon fault. This fault is parallel to the North Pyrenean fault, which is the trace of the rotation of Spain relative to Europe. The Castellon fault may be connected with the Asturian fault, which is located on the Atlantic side of Spain. A contour map down to the Moho has revealed some new deep features and the results are compared with the previous refraction results. The sedimentary column of the deep north Balearic-Provencal basin is much thicker than that of the eastern part of the Valencia trough and this diversity in the sedimentary infilling is probably related to a difference in the subsidence processes. A comparison of the Valencia trough to the Gulf of Lions shows that the thinning of the continental crust looks similar in both regions but the crust is thinner beneath the Valencia continental shelf than that below the Gulf of Lions. In both regions the Moho rises, possibly at the expense of the continental crust, by a process as yet unexplained (petrological or/and thermal variation?).