Estructura y evolución geodinámica del extremo noreste del margen continental catalán durante el Neógeno


  • R. VEGAS


The neogene structure and geodynamic evolution of the continental margin between the Cape Bagur and the Cape Creus, has heen studied by means of multichannel seismic profiles. This structure is explained in a regional geodynarnic framework: the opening of the Western Mediterranean and the changes of the relative motion between the European and Afncan plates (NNE in the Latest Oligocene and NO in the Tortonian age).

Major margin structures consist of a set of structural highs, grabens and semigrabens infilled by Neogene-Quaternary sediments, whose thicknesses range from 400 m near the coast to 4.000 m in the continental slope. This structures are associated to NE-SW to N-S and NWSE to WNW-ESE fault systems. The NE-SW to N-S system produces the structural configuration of the continental margin and the KW-SE to WNW-ESE is associated to the main basins: Rosas and Bagur.

Three main units have been differenciated in the seismic profiles overlying a pre-Neogene basement: the two lowest units (Oligocene?- Lower Miocene and Middle-Upper Miocene units) are associated with the development of neogene deposits, whilst the third consist of post-Messinian deposits (Plio-Quaternary unit).

The proposed geodynamic evolution of the area includes two stages: (1) latest Oligocene-Burdigalian rifting where extensión was accomodated by NE-SW normal faults and NW-SE transfer faults related to the Burdigalian drifting, (2) Tortonian to Present stage characterized by the blocking of the NE-SW faults and the extensional development of the NW-SE fault trend. Each stage involves a basin geometry and a style of faulting.