Deformed Messinian markers in the Cyprus Arc: tectonic and/or Messinian Salinity Crisis indicators?

Abstract

This paper focuses on Messinian Salinity Crisis (MSC) evaporites in the Cyprus Arc (eastern Mediterranean) using high-resolution reflection seismic and multi-beam data. The results shed new light on the Miocene to Present tectonic evolution of this area and contribute to our general knowledge of the MSC in a deep basin setting. The evaporites and overlying formations show a complex deformation pattern due to a combination of thick- skinned plate-tectonic convergence and thin- skinned disharmonic deformation related to the mobile evaporite-bearing unit. Several MSC markers are identified and precisely mapped: the base of the MSC unit is a ‘decollement’ level, whereas the top is clearly identified as a toplap surface. Intra-MSC markers and two MSC subunits are identified and mapped over the entire study area. The geometry of MSC markers shows that the lower MSC subunit was deposited in a relatively quiet tectonic setting. The nature of the anisopachous upper unit indicates a syn-depositional phase of large- scale plate-tectonic activity. A thin- skinned phase of compressional deformation during the Late Miocene affected the entire MSC unit, overlain by undeformed Pliocene-Quaternary layers. A second thin- skinned phase, well expressed in the bathymetry, occurred from the Pliocene to Recent, resulting in extensional gravitygliding within the evaporites and the Pliocene-Quaternary sequence. We show that the MSC had a dramatic impact on the regional structure. For instance, the erosive nature of the top of the MSC unit is linked to the desiccation episode rather than to the cessation of tectonic activity. This particularly strong and short-lived erosion may have been enhanced by the regional effects of the MSC, owing to differential uplift/subsidence caused by the drawdown. The evaporites are essential markers for constraining the tectonic framework, provided that active deformation can be distinguished from passive gliding associated with extensional/contractional deformation.