Marsili and Cefalù basins: The evolution of a rift system in the southern Tyrrhenian Sea (Central Mediterranean)

Abstract

The Marsili Basin (in the southern Tyrrhenian Sea), whose mode of extension is still a controversial issue, is the youngest bathyal basin of the Central Mediterranean. A thin sedimentary cover in the basin permits to image basement fabric and structure by swath mapping and seismic reflection data. We investigate the crustal structure of the southern Tyrrhenian Sea, extending from the bathyal Marsili Basin to the adjacent Sicily continental margin. Interpretation of seismic reflection profiles (calibrated by well and dredge data) and crustal cross-sections were used to identify the stratigraphic infill, structural pattern and large-scale crustal features of the region. We recognized three basins in the southern Tyrrhenian Sea: (1) the Termini basin that is an overfilled sedimentary basin on the continental shelf area; (2) the Cefalù basin, located on the continental slope area and filled by thick deep water turbidite deposits; (3) the distal Marsili basin, filled by hemipelagic and thin distal turbidite deposits. The sequence stratigraphy interpretation permitted us to recognize fourth-order depositional sequences and the stratigraphic signature of the rift stages. An important increase in the sedimentary supply from the continental shelf to the bathyal basin occurred approximately over the last 0.5 Ma and is related to the uplift of the coastal area. The stratigraphic constrains indicate a Lower Pleistocene age for the opening of the southern Tyrrhenian Sea basin. The structural map reveals a complex fault pattern, in which coeval normal faults disclose a triangular basin from the Marsili bathyal basin to the Sicily continental margin, associated to an Euler pole in the northern Sicily. Tacking in account the faults pattern that developed in the whole Southern Tyrrhenian Sea during the Lower Pleistocene, we reconstructed two opposite triangular basins separated by a perpendicular rift. For analogy with the contiguous Vavilov basin, we propose that the extension in the Marsili basin reached the mantle exhumation stage.