--> Influence of salt on structural style in extension and inversion of the Algarve Basin, Portugal

European Regional Conference and Exhibition

Datapages, Inc.Print this page

Influence of salt on structural style in extension and inversion of the Algarve Basin, Portugal

Abstract

The Algarve Basin is a Meso-Cenozoic sedimentary basin lying on top of the Carboniferous basement located in the southwestern margin of the Iberian Peninsula, north of the present day Africa-Iberia plate boundary. The Algarve Basin developed as a rift basin associated to the opening of the North and Central Atlantic Ocean and westward propagation of the Tethys Ocean during the breakup of Pangea. The Basin comprises sedimentary rocks from Upper Triassic through Lower Cretaceous. The main depocenter, up to 3 km thick, is located in the central part of the offshore Algarve Basin. Onshore, the basin crops out along south Portuguese coast, irregularly penetrating to the hinterland between 3 and 25 km. Its structure reveals a prolonged tectonic history comprising various pulses of Mesozoic extension and Cenozoic compression.

The basin extends as much as 100 km offshore, as recognised in several seismic surveys and 5 wells. The southern basin boundary, located offshore, is represented by the Gulf of Cadiz Basement High, having a NE-SW trend.

This work deals with the structure along the northern margin, where the Mesozoic extensional and Cenozoic inversion structures crop out. The strike of the extensional structures ranges from E-W to N-S and the contractional structures are inverted extensional structures, following the same trend. Influence of Upper Triassic/Hettangian salt is well documented offshore (e.g. Matias et al., 2011), while onshore it is less understood. It is argued that the thickness of the Hettangian evaporite layer determines the structural style throughout the basin during the extensional and inversion episodes. The basin is affected by thick-skinned deformation in the northern margin of the basin, where salt is thin or absent, such as basement involved fault systems and short-cut structures. On the other hand, basinward, i.e. as the Hettangian salt thickens, the margin is affected by thin-skinned deformation, such as listric and down-to-the-basin growth faults, diapirism and salt-cored detachment folds. The aim is to discuss the origin of tectonic features, the relevance of salt, and understand their relevance for regional tectonic evolution.