Estratigrafia sísmica do Cenozóico na plataforma continental algarvia: interpretação do controlo tectónico da sedimentação

Abstract

Keywords: Algarve; continental platform; Cenozoic; seismic stratigraphy; tectonics; basin analysis. The interpretation of 64 seismic reflection profiles in the algarve continental platform (36º20' - 37º00' paralels and 7º20' - 8º40' meridians) calibrated with five petroleum exploration wells, with the identification of the geometric relations between six Cenozoic seismic units (B to G) and teetonic structures, allowed the construction of sucessive time-isopach maps (twt/s) and detailed interpretation of the geologic evolution. Two major tectonic structures were identified: a) the Portimão-Monchique fracture zone (striking N-S); b) an off-shore NW-SE fault zone, probably the S. Marcos-Quarteira fault. This accident separates two tectonic domains: the western domain (with N-S and E-W predominant structures and, secondarily, NW-SE and NE-SW) and the eastern domain (dominated by WSW-ENE, NW-SE, NE-SW, NNE-SSW'and NNW-SSE structures). A persistent halokinetic activity had two major moments: a) sin-C unit; b) sin- and post-E unit. An increasing flexuration of the margin was identified, with spacial and temporal variation of the subsidence. The tectonic regime is considered as generally compressive, but the interpretation of the successive stress-fields is rendered difficult by the existence of tectonic sub-domains and evaporitic structures.