Implications of seismic data for the structural evolution and numerical modelling of the Eastern Mediterranean Basin
Libby, Simon Austin
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The Eastern Mediterranean region includes several diverse tectonic domains. Their complexity and interaction have led to competing theories for the region’s evolution. This study aims to resolve some of these issues by using interpretations of regional seismic reflection data located in the offshore waters of Cyprus, Syria, Lebanon and Israel. The extent of the available data is unprecedented for a single study in the area, and the academic nature of the study means the remit is not constrained by political boundaries. The interpretations facilitated a new regionally consistent understanding of the tectonic evolution of the area that included several key conclusions. On the basis of literature review and regional seismic data, the western boundary of the ‘Sinai Plate’ that underlies the Eastern Mediterranean was concluded to run further west than is commonly drawn. However, the ‘Sinai Plate’ may not represent a true tectonic plate as it is not fully rifted at the Gulf of Suez. This study had access to a seismic data set from offshore Syria that only a single published paper had previously investigated. This allowed numerous new observations of a relic subduction zone beneath the Cyprus Arc to be made. The structural restoration constrained by these observations required a restructured plate evolution that included the arrival of the subduction zone in the latest Cretaceous, and provided the keystone to a new explanation for a set of normal faults mapped in the Levantine Basin. These layer-bound normal faults exist spatially and temporally where one might expect compressional features. The interpretation of the regional seismic data more than doubled the area documented as being affected by this deformation, and highlights a set of anticlines that are perpendicular and contemporaneous to the faults. Numerical analysis was conducted on detailed 3D interpretations of the faults using purpose-written software. In combination with observations from seismic data, this analysis provided evidence that contradicted previously published explanations, and suggested the shear system associated with the formation of the neighbouring Levant Shear Zone could have generated the deformation. Both Wilcox-strain-ellipse and extension associated with tectonic indentation of Eurasia contributed to the deformation. Seismic lines over the enigmatic Eratosthenes Seamount with a significantly higher fidelity than those in previously published work showed features that included prograding foresets and an erosive escarpment. These previously undocumented features formed the basis for an updated evolution of carbonate growth on the feature. A depression surrounding the bathymetric high is defined by an external escarpment. Numerical modelling of halokinetic deformation supports inflation of an evaporite body as the explanation for the formation of this depression. Well-imaged internal salt reflectors also indicate an episode of halokinesis immediately after evaporite deposition, contrary to some published interpretations. The new regional insights and detailed interpretations of localised features observed in the newly available 3D datasets are summarised in a series of maps detailing the evolution of the area.