Residual topography, lithospheric structure and sunken slabs in the central Mediterranean

The central Mediterranean comprises subduction, collision, and backarc exte nsion, all in a relatively small area. In this paper, we analyze the topogr aphy of this region, examining the influence of subducting slabs on overrid ing plates. We take the observed surface elevation, remove the contribution of the crust to it and use the residual topography to identify regions tha t are unusually low, unusually high, or normal. Then, we calculate lithosph eric thickness where local isostasy applies. The results provide informatio n about the structure of the lithosphere in this complex region and about t he vertical tectonics. In particular, we found a difference between the sou th Tyrrhenian subduction zone and the Apennines, consistent with the proces ses of slab rollback and slab break-off, respectively. In the south Tyrrhen ian the edge of the oceanic plate is strongly pulled down whereas the edge of the overriding plate (the Calabrian Peninsula) is uplifted. This opposit e trend indicates weak plate coupling - that is, the subducting slab, which is rapidly rolling back hangs almost entirely on the oceanic plate and the overriding plate is free. In contrast, in the Apennines high residual topo graphy and uplifting are detected on both sides of the mountain belt, consi stent with complete break-off of the subducted lithosphere. (C) 2001 Elsevi er Science B.V. All rights reserved.