EVOLUTION OF THE CENTRAL CATALAN MARGIN OF THE VALENCIA TROUGH (WESTERN MEDITERRANEAN)

The evolution of the central Catalan margin was conditioned by major fault activity and thermal processes generated by crustal thinning. The continental margin structure is characterised by major NE-SW-striking, southeast-dipping basement faults which have given rise to a graben, half-graben and horst system. These faults acted essentially as normal faults. No major Neogene strike-slip activity has affected the continental margin, although minor episodic variations from the dominant extensional regime to strike-slip tectonics cannot be discounted. Two major structural evolutionary stages took place at the margin, the transition from one stage to the other being gradual: (1) rifting stage (Late Oligocene? to early Burdigalian) related to the opening of the Valencia trough and from which originated both the Barcelona and Valles-Penedes half-grabens; (2) thermal subsidence stage (late Burdigalian to present) generated by the subsequent crustal cooling and thinning. Fault activity during this stage was essentially concentrated in the major half-graben bounding faults. The sedimentary evolution of the central sector of the Catalan margin was controlled by the tectonic and crustal evolution as well as by the successive sea-level and paleoclimatic changes which affected the region. Drastic changes in the depositional systems took place during the transition from the rifting stage into the thermal subsidence stage. During Aquitanian-Langhian time-characterized by an overall trend of pulsating encroachment of marine conditions over the continental margin-a noticeable diversity of depositional systems (alluvial, lacustrine, coastal evaporitic, fan delta-bay-shelf, carbonate platform systems) developed. From the latest Serravallian up to the present, the depositional framework was less varied due to a general lowering of sea-level and to the final onlapping of most of older structural highs, which are now buried below the Miocene sediments. Two progradational terrigenous shelf-talus systems separated by the Messinian erosive surface developed during the latest Serravallian-Tortonian and Pliocene-Quaternary.