Evolución del sector septentrional del margen continental catalán durante el Cenozoico



Preliminary integrative analysis of the geological record in the onshore and offshore areas of the Northern Catalan continental margin, enable one to trace as far as the shelf edge, the main Eastem Pyrenean Paleogene contractive structures (axial zone antiformal stack, Figueres-Montgrí thrust-sheet, Vallfogona thrust) and their coeval foreland basin. These structures are cut by two major, NE-SW to NNE-SSW and NW-SE oriented, extensional fault systems. The activity of the NE-SW to NNE-SSW fault system (mainly Late Oligocene-earliest Miocene in age) would have resulted in most of the crustal extension and thinning recorded in this extensional margin of the Valencia Trough. On the other side the NW-SE faults were at least partially active as strike-slip faults during the Paleogene, with displacements which are difficult to be precised. Nevertheless these faults were mainly normal faults during Middle Miocene to Quatemary. Although the faults display minor slips than those of NE-SW orientation, they are closely related to a noticeable alkaline volcanic activity which denote they reach the lower litosphere. The Cenozoic stratigraphy in the Northern Catalan continental margin records and was influenced succesively by: 1) the Paleogene (Paleocene-Early Oligocene) upbuilding of the Pyrenean orogen and the evolution of its foreland basin; 2: the activity of the Late Oligocene-Early Miocene NE-SW to NNE-SSW faults and coeval lithospheric uplifting, both related to the the NW Mediterranean rifting; and 3: the later thermal subsidence of the continental margin developed during the Middle Miocene-Quaternary and which was opposite to the isostatic rebound of the Pyrenees and its southern foreland. Middle Miocene to Quaternary sedimentation related to the resulting total subsidence of the continental margin was modified by the generation of local depocenters. These depocenters resulted from the excavation of topographical depressions and the more or less simultaneous activity of the NW-SE faults. Some of these low lying zones were superimposed and accentuated pre-existing contractive Paleogene depressions. In some cases this fact controlled the develoment of significative Late Neogene depocenters and the location in the continental margin of some conspicuous Neogene and recent submanne canyons.

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