Pliocene-Quaternary Deformational Structures in the Eastern Algarve Continental Shelf, Gulf of Cadiz

Abstract

The eastern Algarve continental shelf in the northern margin of the Gulf of Cadiz has been investigated by analysing a set of high-resolution seismic reflection profiles. We examine the major structural elements affecting the upper sedimentary units. A seismo-stratigraphic interpretation and regional correlation allowed the identification of a major discontinuity that separates two main intervals, pre-Middle Pleistocene (MP) and post-MP. In addition, a number of deformation features such as ENE-WSW to NE-SW thrusts, kilometric-scale N-S to NW-SE folds and NNE-SSW to NNW-SSE sub-vertical normal faults were identified affecting the Pliocene-Quaternary sedimentary record, indicating neotectonic activity. The structures pre-dating MP are in agreement with a dominant transpressive regime along the continental shelf, under the Late Cenozoic NW-SE oblique convergence and related to the reactivation of Mesozoic diapiric structures. The structures post-dating MP induce a lower deformation of the sedimentary cover but were still active during the last glacial maximum, in agreement with the low uplift recognized in the Portuguese mainland.