Oblique Convergence Along a Crustal Discontinuity in Western Sicily

Abstract

The results of an integrated stratigraphic, structural, geophysical and geochemical study reveal the presence of a crustal discontinuity in western Sicily that, at present, runs roughly N-S along a band from San Vito Lo Capo to Sciacca (SVCS). This discontinuity separates a western sector with normal crustal thickness from an eastern one floored by a thinned crust. The boundary between the two zones is nearly orthogonal to the main thrust propagation of the Sicilian thrust and fold belt. To this discontinuity appear related the different Permian to Tertiary sedimentary evolution recorded by the two zones, with thick carbonate platforms in the western sector facing deep-water successions in the eastern one. Along the transition zone the presence of Upper Triassic reefs, huge megabreccias bodies and widespread submarine volcanisms account for the presence of a long lasting weakness zone reactivated time by time by transpressional or transtensional stress fields in relation to the different geodynamic regime of the central Mediterranean area. We speculate that this transition zone has represented a segment of the passive margin of the Ionian Tethys. During the Maghrebian convergence a different style of deformation has affected the two sectors floored by different sedimentary multilayers. The orthogonal to oblique differential convergence between the two sectors has resulted in right-lateral transpressional motions leading to oblique thrusting of deep-water-derived thrusts onto platform-derived thrusts associated to clockwise rotations. The oblique convergence is still ongoing as demonstrate by the seismicity of the area, by the geothermal field with high mantle-derived helium fluxes and by the GPS data performed by different authors. The structural model developed on the base of our data should be taken into account for future hydrocarbon exploration in western Sicily.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015