Post-salt carbonates control salt-tectonic minibasin formation

Abstract

Salt tectonics on passive margins are driven by sediment loading and gliding with minimal influence from basement-involved tectonics and is associated with variable and complex salt structures, such as minibasins and diapirs. A major enigma in salt tectonics is the origin of load-driven diapir-flanked minibasins, synclinal depocenters formed by localized subsidence of synkinematic sediments into salt. How can less-dense clastic sediments sink into the denser salt, promoting diapirism at their flanks? We use two-dimensional numerical modeling of lithospheric extension including syn- and post-rift sedimentation to understand the evolution of salt-tectonic minibasins along rifted passive margins. Our results show that these minibasins are driven by deposition of dense early post-salt carbonates and then amplified during progradation of less-dense and compacting clastics. In contrast, basin-scale salt flow driven by clastic progradation alone, without deposition of early post-salt carbonates, does not produce minibasins as observed on salt-bearing passive margins.