Lithospheric structure beneath the Alboran Basin: Results from 3D gravity modeling and tectonic relevance

A three-dimensional gravity modeling combined with integrated heat flow and elevation modeling is conducted to map out the crustal and lithospheric ma ntle thickness in the Alboran Basin, in the westernmost Mediterranean. A "s ediment"-corrected Bouguer anomaly has been derived using a depth-to-the-ba sement map and densities determined from well logs and seismic data. The gr avity effect of the base of the lithosphere has been removed from the sedim ent-corrected Bouguer anomaly to obtain a "crustal" Bouguer anomaly, which has been inverted for crustal thickness. The resulting lithospheric structu re is further constrained by elevation data under the assumption of local i sostasy. The low residual elevation anomalies obtained (+/-100 m in average ) suggest that the area is in local isostasy, particularly the medium- and long-wavelength topography features. Variations in crustal thickness range from 36 km underneath the Betic and Rif Chains to <12 km beneath the easter nmost part of the Alboran Sea Basin, in the transition to the South Baleari c Basin. In western Alboran the Moho lies at a rather constant depth of sim ilar to 18 km, deepening sharply toward the Gibraltar Strait down to 30-32 km. The base of the lithosphere shallows from 140 km depth in the Gibraltar Strait to <45 km depth in the easternmost Alboran Sea. Lithospheric thinni ng penetrates to the southeastern side of the Iberian margin crosscutting t opographic highs of the central and eastern Betic Chain. Our results favor mantle delamination produced by detachment and subsequent peeling away of t he lithospheric mantle rather than convective removal of the lithospheric m antle either by orogenic collapse or detachment and sinking of a lithospher ic slab.