Crustal Thickness and Oceanic Lithosphere Distribution in the Eastern Mediterranean from Satellite Gravity Anomaly Inversion

The distribution of oceanic and continental lithosphere in the eastern Mediterranean is not well understood. Gravity inversion, incorporating a lithosphere thermal gravity anomaly correction, has been used to map Moho depth, crustal thickness and continental lithosphere thinning factor for the eastern Mediterranean in order to determine the distribution of oceanic and continental lithosphere and the ocean-continent transition location. Data used in the gravity inversion are bathymetry, free-air gravity and sediment thickness data from Smith and Sandwell (1997), Sandwell and Smith (2009) and Laske and Masters (1997) respectively. Moho depths from the gravity inversion are dependent on the age of oceanic lithosphere and continental breakup because of the lithosphere thermal gravity correction; however, these ages are uncertain for the eastern Mediterranean. Gravity inversion sensitivities to break-up ages of 225Ma (late Triassic) and 100Ma (early Cretaceous) have been examined. Gravity inversion results show thin crust (5 - 10km thickness) for the Ionian Sea and the Herodotus Basin of the eastern Mediterranean consistent with these basins being underlain by oceanic or highly thinned continental crust. Predicted Moho depths from the gravity inversion are in agreement with published Ionian Sea ESP results (Voogd et al, 1992) and suggest a gravity inversion reference Moho depth increasing to the north, which we attribute to subduction dynamic subsidence. Calibration of gravity inversion Moho against ESP results show a trade-off between break-up age and reference Moho depth; a Cretaceous age ocean requires a larger Moho reference depth than a Triassic age ocean. Lithosphere thinning factor maps from gravity inversion for Africa do not show continuity between the Cretaceous African rift system (Benue Trough, Chad, CASZ and Sudan basins) and eastern Mediterranean basins. If the Ionian Sea is of Cretaceous age then it more probably links to Cretaceous rifting and sea-floor spreading to its north and north-west.