Middle–Late Eocene structure of the southern Levant continental margin — Tectonic motion versus global sea-level change

Abstract

During the Paleogene greenhouse episode Earth experienced the warmest period of the Cenozoic while global sea level rose by more than 100 m. However, geological evidence from the Levant margin, northwestern Arabian plate, indicates that throughout this period seabed deepening exceeded 1000 m. Lithology from Israel, Syria, Lebanon and Jordan is mainly pelagic and neritic, interfered by occasional fossil sub-marine slumps. In order to understand this dissimilarity we quantify the vertical tectonic motion of the Levant continental margin through the Paleogene. The margin began to take shape during the Late Permian and it was reactivated during the Oligocene. Based on information from outcrops, drillholes, seismic reflection and refraction, gravity, and previous publications, a multi-layered model of the Levant lithosphere was established. Layers include the Moho, top of the crystalline basement and covering sediments up to the Late Eocene. The model was restored horizontally by 100 km along the younger Dead Sea transform. Assuming local isostatic compensation, vertical restoration yielded the paleo-bathymetry which prevailed across northwestern Arabia during the Middle–Late Eocene. Results show that following the margin subsidence the Cretaceous Levantine platform became ramp shaped during the Eocene. Most parts of the central Levant were submerged under ~ 200 to ~ 1800 m of water, while the paleo-bathymetric gradients ranged from ~ 2° at the shelf to ~ 6° at the slope. The apparent dissimilarity between sea level and our tectonic-based calculations is up to an order of magnitude. These differences may be resolved by accounting for vertical tectonic motions and sediment supply rates. Our results stress the importance of the presented crustal structure. As opposed to the backstripping procedure, the structural map of the top Eocene interface was constructed upwards from the well established top Turonian (Judea Group) interface since only scarce and sporadic outcrops of the target horizon are available. We suggest that a similar approach should be applied to re-evaluate the depositional environments across the entire continental margin of the eastern Mediterranean, an area with proven hydrocarbon prospects.