Chapter 16 – Salt Tectonics Within the Offshore Asturian Basin: North Iberian Margin

The Asturian Basin is one of several basins developed in the North Iberian Margin during the opening of the Bay of Biscay. The infill of the basin ranges from the Upper Paleozoic to the present, holding a thick Mesozoic sedimentary sequence with Keuper evaporites at the base and up to 4000 m of Jurassic and Cretaceous deep marine sediments. The structural architecture of the offshore Asturian basin is strongly related to salt tectonics. We present new interpretations showing minibasin-scale halokinetic features, diapir geometry, and presalt structures that illustrate the relationship between diapirism and regional tectonic events. Two salt tectonic domains are identified based on the style of salt deformation: a Western Salt Domain, dominated by vertical salt walls, and an Eastern Salt Domain toward the deeper part of the basin, with fewer diapirs and more salt-detached thrust faults. Additionally, this domain shows more prominent salt sheets with greater lateral extent. We propose a halokinetic structural evolution that is representative for the interpreted salt-related structures: (1) Early Permian to Triassic stretching was followed by Keuper evaporite deposition; (2) Upper Jurassic to Lower Cretaceous rifting triggered reactive to passive diapirism over the footwalls of presalt normal faults; and (3) Paleogene shortening caused existing diapirs to be rejuvenated and squeezed, developing salt sheets before getting buried by the Miocene posttectonic sediments.