Stratigraphy and structural evolution of the messinian evaporite complex of the Eastern Mediterranean
Creators: name: Allen, Hayley
Publisher: name: Imperial College London
Year: 2014

description: The offshore Eastern Mediterranean constitutes an area of c. 250,000 km2 and is located on the northern margin of the subducting African plate. It is a region of numerous tectonic domains that have resulted in a complex, high-relief crustal structure of sub-basins and highs. Superimposed on this complicated structural framework and Mesozoic-Cenozoic sedimentary fill is a vast salt succession, which we term the Messinian Evaporite Complex (MEC), that is locally &gt;3 km thick and has a total volume of ~1 million km3. The evaporites were deposited between c. 5.96-5.33 Ma as a result of the Messinian Salinity Crisis, a major evaporitic drawdown event affecting the Mediterranean basins, resulting in the deposition of this vast salt deposit in the deep basins and widespread incision at the margins. The overwhelming majority of previous research conducted on the MEC has focused on isolated outcrop or sub-surface studies from relatively marginal settings, despite the fact that much of the salt sits out in the deep basin. This has led to confused stratigraphic schemes and much debate over the origin, extent and timeframe for the deposition of the MEC. This thesis aims to progress understanding of the structural and stratigraphic development of the MEC in the deep basin by utilizing regional 2D seismic surveys and a high-resolution 3D seismic cube (covering a total area of c. 180,000 km2) underpinned by marginal well data to perform comprehensive seismic facies and structural analyses of evaporites across the eastern Mediterranean sub-basins. For the first time in the literature, we present systematic interpretations of the variability of seismic facies and structural styles of the MEC at a regional scale across the Eastern Mediterranean. Our research has revealed a thick succession of up to seven alternating high to low amplitude, laterally persistent seismic sequences in the Levantine Basin, which display high levels of internal deformation. These stacked sequences pass abruptly into an evaporite interval dominated by transparent seismic facies, with high levels of mobility, producing classical salt-tectonic structures affecting both the salt and overburden in the Herodotus Basin. A series of structural domains have also been identified that are related to on-going, thick-skinned, collisional tectonics in the region and thin-skinned, gravity processes associated with the Nile Delta and Levant margin. The project therefore offers a unique opportunity to study the impact of major sea-level fall on facies and depositional patterns during the early stage tectono-stratigraphic evolution of a saline giant. This has led us to propose new models for the stratigraphic and structural development of the region, and poses new questions regarding the effect of these facies variations on calculated velocities and therefore, depth migration and conversion attempts. The relative youth of this saline giant makes it an excellent natural laboratory, offering exciting new insights into the structural and stratigraphic complexity of evaporite-bearing successions. In terms of its youth and depositional timeframe, the MEC is unique, although the processes we document here may be applicable to other salt-bearing sedimentary basins worldwide.