Arquitectura estratigráfica de los depósitos del Plioceno- Cuaternario en las plataformas continentales del Sur de la Península Ibéricasu relación con los cambios eustáticos y paleoceanográficos

Resumo

A Quaternany stratigraphic stacking pattern on the continental shelves of the southern Iberian Peninsula has been determined by analysing and comparing a dense network of low-, medium-, high- and very high-resolution mono-channel and multi-channel reflection seismic lines and welllog data. Four major low-resolution depositional sequences related to a 3rd-order cycle at 1.51.6 Ma have been recognised in the Pliocene-Quaternary sedimentary record (M/P1, P2, P3/ Ql y Qll). They are separated by three discontinuities corresponding to the most drastic changes in climate and palaeoceanography affecting the Atlantic and Mediterranean linkage, and especially to the most prominent sea-level falls in the Messinian (M) at 5,5 Ma, in the lower Pliocene at 4,2; in the Upper Pliocene at 2.4 Ma (UPR), and in the Mid Pleistocene at 900920 ky (MPR). These major sequences were built up by asymmetrical sea-level cycles, which the regressive and lowstand system tracts are the best deposits, controlling the main progradation of the shelf. The Quaternary shelf stratigraphy can be divided into minor asymmetric depositional sequences of 4th-order, but the overall architectural stacking shows a clear change after the MPR discontinuity attributed to the onset of the 100 ky eccentricity orbital cycles, which abruptly increased the amplitude of sea-level variations (100120 m) during the last 900920 ky.