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Hydrographic structure and nepheloid spatial distribution in the Gulf of Lions continental margin

1990; Elsevier BV; Volume: 10; Issue: 9-11 Linguagem: Inglês

10.1016/0278-4343(90)90067-v

1873-6955

Xavier Durrieu de Madron, F. Nyffeler, Charles-Henri Godet,

Geological and Geophysical Studies Worldwide

A general hydrographic and nephelometric survey of the Gulf of Lions margin was undertaken, under autumn conditions. The distribution of suspended material along the margin during this experiment is controlled, at least in part, by the following factors: (a) the hydrography of the shelf-slope waters, i.e. the nepheloid layers follow the isopyenals; and (b) the cyclonic circulation of the water masses (the Liguro-Provençal Current and, in particular the proximity and depth of the Levantine Intermediate Water circulation). On the northeastern part of the margin along the slope, the seaward extension of the nepheloid layers is sharply bounded and is concentrated in canyon heads by the general water circulation. In the southwestern part, the decreasing depth of the major flow of the general circulation and its increased distance seaward from the upper slope allow the seaward and downward expansion of the nepheloid structures. The suspended material extending offshore is swept away and diluted by the general circulation. The stepwise increase toward the southwest, in suspended particulate contents in the slope waters between the northeastern and southwestern ends of the Gulf of Lions, is assumed to be due mainly to inputs from the shelf through the canyons. The Marseille canyon, at the northeastern part of the Gulf of Lions margin, is influenced less by the Rhoˆne and other rivers of the shelf. The influence of the Rhoˆne is seen first at the longitude of the Rhoˆne's canyons. In the southwestern part of the Gulf, the Bourcart and Lacaze-Duthiers canyons are areas through which the suspended material, originating from the whole shelf, passes.