The influence of base-salt relief, rift topography and regional events on salt tectonics offshore Morocco

Abstract

Abstract This study integrates borehole-calibrated 2D and 3D seismic interpretation with numerical models to provide a regional analysis of the complex salt tectonics offshore central Morocco. We investigate the mechanisms controlling along-margin structural variations, the effects of thick-skinned shortening and the sequential evolution of allochthonous sheets. Additionally, we analyse how base-salt relief generated complex flow kinematics and alternation of extensional and contractional domains by causing flux variations at both autochthonous and allochthonous salt levels. The area is divided into three structural provinces, with the central, Essaouira segment, having greater downdip translation, structural complexity and volume of allochthonous salt, which suggests the salt was originally thicker and better connected across multiple syn-rift structures. The southern segment, Agadir, is dominated by up-right squeezed diapirs formed by early load-driven rise and late shortening; limited salt and overburden translation and no allochthonous sheets. The northern segment, Safi, is narrower and has a smaller number of salt structures that were affected by abrupt translation due to steep detachment gradient. Late, oblique thick-skinned shortening generated contractional structures in the entire salt basin, which are most prominently developed in Essaouira due to a favourably-oriented NW-SE syn-rift structure, the Talfeney Accommodation Zone. Allochthonous salt sheets formed during four phases from the Albian, Late Cretaceous, Paleocene to Oligo-Miocene by two main mechanisms: contraction and basinward salt expulsion. This work improves understanding of the structural configuration along the Moroccan margin guiding the identification of potential sub-salt plays and contributing to a better comprehension of salt-related deformation along rifted passive margins worldwide.