AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin

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High hopes: Esperança salt revisited

Abstract

Recent activity in hydrocarbon exploration offshore Portugal, in particular in the Algarve basin, has increased the interest in salt tectonics studies in this area. Development of a comprehensive study of the petroleum systems of this basin is inevitably connected to the analysis of the salt system and related tectonics. The geological history of the Algarve basin includes extension episodes through Triassic, Jurassic and Early Cretaceous, followed by tectonic inversion since Late Cretaceous due to the Europe-Africa compression. Recent studies of the basin identify the presence of two separate evaporitic units. The deepest one is an autochthonous unit deposited during the first stages of extension, Late Triassic – Early Jurassic (Hettangian), and it is present throughout the Algarve basin. The shallowest evaporitic unit (also called Esperança salt), as per reflection seismic interpretation, is thought to be placed between the Jurassic and Cretaceous sequences and its presence is restricted to the eastern side of the Algarve basin. This study presents results from the interpretation of a reprocessed regional 2D seismic survey and a 1500 km2 3D seismic survey, integrated with gravity and magnetics data. It focuses in the eastern part of the Algarve basin, were the allochthonous salt unit has been previously described by various authors. The work tries to summarize the historic research regarding this feature and provide new ideas by analysing key sections of the mentioned surveys that help understand its age and origin and alternative interpretations.