The meeting place of backarc and foreland rifting: The example of the offshore western Sicily (Central Mediterranean)

Coeval rifting processes affecting both backarc, thrust belt and foreland occurred in offshore western Sicily (Central Mediterranean) as indicated by the analysis of a large seismic data set calibrated with well data, onshore data and dredges in a dedicated GIS software environment. Structural pattern of the investigated area, 3-D geological models and a Pliocene-Lower Pleistocene evolution of extensional sedimentary basins have been reconstructed. In detail, two zones characterized by basins with different directions of extension have been recognized: one trending NE-SW, located south of the Egadi Islands; another trending E-W, positioned north of the Egadi Islands. The first group of basins represents the continuation of those of the Africa foreland basin (Pelagian Block), as the second one characterizes the opening of the backarc (southern Tyrrhenian margin). Both basins affect the collisional chain (Maghrebian thrust belt). An eastward progression of extension, from lower Pliocene to lower Pleistocene, based on different onset of the basin fill, has been documented in the Southern Tyrrhenian margin. The study area represents the meeting place of backarc and foreland rifting that affected the late Miocene thrust belt. The recognized pattern of extensional deformation of the upper plate adds some constraint on the geodynamic evolution of the African and Eurasia plates and supports a model of westward dipping slab in the Central Mediterranean. It is hypothesized that the along-trench variation of the nature of the plates, due to paleo-margin configuration, has a profound impact on the upper crustal deformation during the convergence and thus the meeting place of backarc and foreland rifting could represent the surficial signature of the slab detachment since Pliocene times.