Gravity Inversion Mapping of Crustal Thickness and Lithosphere Thinning for the Eastern Mediterranean and North Africa

Cowie, Leanne ¹; Kusznir, Nick J.¹
(1)Earth Interior Dynamics, University of Liverpool, Liverpool, United Kingdom.

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 and North Africa in order to determine the distribution of oceanic lithosphere, ocean-continent transition and continental rifting. 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 consistent with published seismic results (Voogd et al, 1992). The predicted basement crustal thickness at the north African coast has values of less than 30km, substantially less than in the continental interior to the south, possibly corresponding to the relict Tethyan margin. Continental lithosphere thinning factor maps from gravity inversion for Africa do not show rifting continuity between the Cretaceous African rift system (Benue Trough, Chad, CASZ and Sudan basins) and the 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. Continental lithosphere thinning and post-breakup residual thicknesses of continental crust determined from gravity inversion have been used to predict the preservation of continental crustal radiogenic heat productivity and the transient lithosphere heat-flow contribution within thermally equilibrating rifted continental margin and oceanic lithosphere. The resulting crustal radiogenic productivity and lithosphere transient heat flow components, together with base lithosphere background heat-flow, are used to produce regional maps of present-day top-basement heat-flow. Data used in the gravity inversion are public domain bathymetry, free-air gravity and sediment thickness data from Smith and Sandwell (1997), Sandwell and Smith (2009) and Laske and Masters (1997) respectively.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.