Structure and present-day compression in the offshore area between Alicante and Ibiza Island (Eastern Iberian Margin)

Abstract

This study deals with the structure and recent deformation of the Eastern Iberian margin, extending from basement to seafloor and including the south-western margin of the Valencia Basin, the Alicante Shelf, the Ibiza Channel and its southern margin descending into the Algerian Basin. This area underwent a complex tectonic evolution linked to the back-arc opening of the North-western Mediterranean and the concomitant contraction of the Betic belt due to the collision with blocks located between Africa and Europe. This Oligo-Miocene structural heritage gave rise to a complex and continuous deformation through times including Late Miocene post-orogenic extension and Pliocene to Quaternary compression in the western Balearic area and coeval extension in the Valencia basin.This study presents maps of the depth to basement and Base of the Pliocene, as well as bathymetry data and seismic lines, which provide a precise integrated 3D study of the offshore domain. It reveals a major reactivation of the area, represented by the N80 to N60 trending structures, small discontinuous folds and thrusts in the Ibiza Channel and a large flexure on the Alicante shelf. The structures are picked out by erosion surfaces or deposits linked to the Messinian Salinity Crisis (MSC). These markers are ubiquitous in the seismic sedimentary sequences and record the lateral and vertical deformation active from the Messinian Salinity Crisis to the Present. The contraction in the western Iberian margin and concomitant extension in the southern Valencia Basin are consistent with the regional stress field as determined from the focal mechanisms of offshore earthquakes or recent GPS measurements. The tectonic compression of the studied area casts doubt on the eventual propagation of the present-day compressive stress from the Algerian margin to the Western Balearic Promontory.