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The Algarve Basin is a Meso-Cenozoic sedimentary basin overlying Carboniferous basement, located in the southwestern margin of the Iberian Peninsula. Its structure reveals a protracted tectonic history comprising various pulses of Mesozoic extension followed by Cenozoic compression. This work deals with the structure along the northern margin, where the Mesozoic extensional structures and Cenozoic inversion structures crop out. The strike of the extensional structures ranges from E-W to N-S, as controlled by a shift from Tethyan-dominated extension in the east to Atlantic-dominated extension in the west. Contractional structures are inverted extensional structures, following their same trends. It is argued that the thickness of the Hettangian evaporite layer exerts a strong control on the structural style throughout the basin during the extensional and inversion episodes. The basin is affected by thick-skinned deformation along the northern margin, where salt is thin or absent, basement involved fault systems and short-cut structures. Basinward, as the Hettangian salt thickens, the margin is affected by thin-skinned deformation, with listric and down-to-the-basin growth faults, diapirism and salt-cored detachment folds. The aim was to discuss the key tectonic features, the relevance of salt, and understand the nature, timing, and significance of all these structures in the regional tectonic evolution. [ABSTRACT FROM AUTHOR]

Western Iberia is considered an archetypal example of a hyper-extended Atlantic margin that has been studied by multiple authors, who have defined its regional-scale structure and mapped out the different tectonic domains. However, to date, there is no detailed mapping of faults, depocenters and other structures at the scale of the entire margin that is fully consistent with the magnitude and temporality of Mesozoic extension and Cenozoic inversion experienced by this margin. Limitations in the data (quality of reflection seismic, ambiguity in interpretation of potential field and seismic refraction data,...) mean that their interpretation is non-unique, making it difficult to converge on a single detailed interpretation without incorporating further constraints.The present study describes the tectonic evolution of the western Iberia margin based on three different sectors; Galicia, Peniche-Alentejo and Algarve-Gulf of Cadiz. Our interpretation indicates that estimates of beta factor (crustal extension) based on fault heaves can be a factor of two less than estimates from crustal thickness derived from refraction seismic or isostatic equilibrium methods. The resulting interpretation has been sequentially restored to identify the structural elements that give rise to the extension discrepancy. These observations have in turn been used to iteratively improve the seismic-based interpretationand reduce the differences between discrepancies in extension measurements.The Mesozoic extensional structure of this margin is further complicated by Cenozoic inversion. Some inversion features elevate features that were already highs during the extensional stage, making it difficult to separate the impact of both tectonic events and being a possible source of the extension discrepancy. We have tried to discriminate the syn-rift structure from post-rift margin inversion along the margin based on gravimetric and magnetic data, seismic and well data.The final result is an interpretation that is our best attempt at honoring all sources of information (geophysical and well data as well as tectonic evolution, structural constraints, subsidence history ...) with the ultimate goal of reducing the uncertainty derived from the non-unique interpretation of the different data sources. [ABSTRACT FROM AUTHOR]

The SW Iberian margin developed as a passive margin during Mesozoic times and was later inverted during the mainly Cenozoic Alpine orogeny. The initial syn-rift deposits include a Lower Jurassic evaporite unit of variable thickness. In the onshore, this unit is observed to thicken basinward (i.e., southward), in fault-controlled depocenters, and salt-related structures are only present in areas of thick initial evaporites. In the offshore, multiple salt-structures cored by the Lower Jurassic evaporites are interpreted on seismic reflection data and from exploratory drilling. Offshore salt structures include the allochthonous Esperança Salt Nappe, which extends over an area roughly 40 × 60 km. The abundance of salt-related structures and their geometry is observed to be controlled by the distribution of evaporite facies, which is in turn controlled by the structure of rift-related faulting. This paper presents a comprehensive study of salt tectonics over the entire onshore and offshore SW Iberian passive margin (southern Portugal and Gulf of Cadiz), covering all aspects from initial evaporite composition and thickness to the evolution of salt-related structures through Mesozoic extension and Cenozoic basin inversion. [ABSTRACT FROM AUTHOR]