Structural highs formation and their relationship to sedimentary basins in the north Sicily continental margin (southern Tyrrhenian Sea): implication for the Drepano Thrust Front.

Abstract

Two high-penetration seismic profiles across the continental margin of north Sicily (southern Tyrrhenian Sea) have been interpreted to construct a crustal section across the margin and to provide a three-dimensional perspective on the upper crustal setting of the Solunto High and its structural relationships with the adjacent Cefalu` Basin. Crystalline rocks of the Kabilian–Calabrian Units (KCU) are recognized in the Solunto High region and farther to the north. The KCU body is tectonically superimposed onto sedimentary rocks pertaining to the Sicilian–Maghrebian Units (SMU) and the Solunto High corresponds to the thrust sheet culmination. Its occurrence in the Solunto High demonstrates that the Drepano Thrust Front is continuous from the Elimi Chain in the west to the Calabrian–Peloritani in the east. At the crustal scale, the continental margin of north Sicily shows tectonics features typical of most subduction zones and of rifted continental margins. Continental collision was achieved in the (?)Oligocene–early Miocene and caused the superposition of the KCU crystalline rocks on the deep-water carbonate resting on the African continental margin. Contractional deformation persisted until the late Miocene resulting in the tectonic superposition of deep- onto shallowwater carbonates and the formation of the Sicilian–Maghrebian fold-and-thrust belt. Extension began in late (?) Tortonian times, lasted till the early (?) Messinian and caused the opening of the Cefalu` Basin and other basins further to the north. Late (?) Messinian–early Pliocene contractional and/or transpressional deformation reactivated previously formed oblique ramps in the inner sector of the thrust belt. This event was responsible for uplift of the KCU in the Solunto High region. In the middle–late Pliocene, renewed extension determined further opening and subsidence of the Cefalu` basin. Lithospheric breakup took place in the late Pliocene. Presently, the north Sicily offshore is a zone of compressive stress and the area north of Solunto High is a zone of weakness.