Mesozoic tectono-sedimentary evolution of the Trapanese SouthernTethyan margin (NW Sicily) integrating facies and stratigraphic analysis with subsidence history

Abstract

Several Mesozoic successions of the Southern Tethyan margin were accumulated on a carbonate platform evolving to pelagic plateau depositional systems. Rifting paleotectonics was the main process conditioning their tectono-sedimentary evolution. The well-exposed outcrops in the NW Sicilian fold and thrust belt of the so-called Trapanese carbonate platform to pelagic succession highlight the occurrence of lateral facies and thickness changes, paleofaults, volcanics, and resedimented deposits. The integration of facies analysis, stratigraphic data, and subsidence history have permitted to decipher the polyphase tectono-sedimentary evolution and to distinguish different depositional settings. Structural lows, filled with up to 100m of pillow lavas and reworked deposits, appear as intraplatform basins bordered by structural highs, as horst ridges, characterised by condensed sedimentation, and isolated seamounts. These sectors were linked among them by stepped fault margins, scalloped margins and depositional slopes. The tectonic history, highlighted by the backstripped sections, reveals superimposed evolutionary stages reflecting rifting and rapid tectonic subsidence, leading to continental break-up (Late Triassic-Early Jurassic stage); the Middle Jurassic stage reflects slow thermal subsidence in the basin shoulders and higher rates in the intervening depressions; the Late Jurassic-Early Cretaceous regional uplift interrupts the thermal subsidence curve trend. The tract of the Late Cretaceous-Eocene curve suggests again slow thermal post-rift subsidence, also influenced by sediment load. The different subsidence curves, reconstructed from different positions in the sedimentary basin, demonstrate that its evolution could be driven by the identified syn-sedimentary faults that were formed and/or re-activated during several tectonic events encompassing the whole Jurassic-Cretaceous time period. The regional significance of this tectonics indicates that the Sicilian sector of the Southern Tethyan continental margin was tectonically active for the whole Mesozoic.The reconstructed paleophysiography of the Trapanese continental margin, during the Mesozoic, appears characterised by a segmented and drowned carbonate platform with morphostructural highs separated by deep channels. The comparison with the present-day morphostructural setting of some regions of the Atlantic continental margins (e.g. Caribbean, Brazilian equatorial margin), suggests also for the study region that the occurrence of transcurrent/transform faults and stretching of the continental lithosphere can have played an important role in determining the physiographic conformation.