Palaeostrait tectonosedimentary facies during late Cenozoic microplate rifting and dispersal in the western Mediterranean

Palaeostraits are common features formed during the extension and fragmentation of active continental margins, when back-arc basins are formed and microplates develop through upper-plate extension. In this contribution, we focus on narrow seaways and straits associated with successive pulses of late Cenozoic rifting along the southwestern Eurasian continental margin, and the ensuing formation and dispersal of microplates. The incomplete and largely non-cylindrical Africa–Eurasia continental collision in the Mediterranean region provides snapshots of the various phases of microplate fragmentation and dispersal, punctuated by the presence of narrow seaways/straits. These peculiar physiographical conditions induced current amplification, and led to the accumulation of characteristic large-scale, cross-stratified deposits and tidal facies in an otherwise generally microtidal setting. Although not univocally related to rifting, the identification of such distinctive sedimentary facies within deformed orogenic belts may ultimately help in terrane analysis and in the discrimination of individual microplates, which were then amalgamated. Recognition and dating of palaeostrait tectonosedimentary facies can thus constrain the presence and the onset of extension in the geological record.