A DEEP-SEA CHANNEL IN THE NORTHWESTERN MEDITERRANEAN-SEA - MORPHOLOGYAND SEISMIC STRUCTURE OF THE VALENCIA-CHANNEL AND ITS SURROUNDINGS

The 400 km long Valencia Channel occupies the axis of the Valencia Tro ugh in the Northwestern Mediterranean. Four different types of seismic reflection profiles were used to analyze the morphology and structure of the Valencia Channel with regard to the role played by both margin s, Balearic and Iberian, of the Valencia Trough. From a detailed morph oseismic analysis of the Valencia Channel, its upper, middle, and lowe r courses can be characterized as follows: (1) in the upper course, tr ibutaries are short and only slightly incised, with recent mass-transp ort deposits occurring on the adjacent continental dopes; (2) in tile middle course, the channel deepens, and tributary valleys merge into i t; and (3) the lower course begins after a sudden change in the direct ion of the channel, has a meandering path, is flanked by levees, and i s fed by some valleys. During the Pliocene and Quaternary, at least fo ur erosional and filling phases are observed in seismic profiles of th e lower course of the Valencia Channel. The varying intensity of mass- transport processes and associated retrogressive slumping, which are r elated with fluctuations in sediment supply and relative sea-level cha nges, have played a major role in the formation, maintenance and deepe ning of the Valencia Channel. In addition to these sedimentary process es, a basement tectonic control and some morphostructural features aff ect the direction of the Valencia Channel locally.