Tectono-stratigraphic evolution of a basin generated by transpression: the case of the Early Pliocene Lascari basin (Northern Sicily)

Integrated stratigraphy and structural analysis carried out in the Madonie Mts. (Northern Sicily) is aimed to the description of a syn-sedimentary tectonic event, recorded in a small infra-pliocene basin restricted to the Lascari Syncline core. The onset and evolution of the basin was driven by transpressive tectonics, generating a lens-shaped, deep and narrow tectonic depression, bounded by steep and high, tectonically controlled slopes, also reflected in the present-day topography of the area. During the genesis of the basin, the tectonic control interferes with a dramatic sea level oscillation during the Messinian-Early Pliocene time interval. In this paper, the syn-tectonic deposits of the Lascari basin are studied using both stratigraphicsedimentology methods and the structural analysis, also considering the deformations affecting the underlying bedrock. The EW trending Lascari Syncline, where the Pliocene syn-tectonic basin is hosted, belongs to a system of north verging folds, deforming the pre-existing, originally flat thrusts , generated in Langhian-Serravallian time at shallower crustal levels. The growth geometry that characterizes the stratal pattern of the Pliocene succession and its basal angular unconformity suggest that the activity of the transpressional event, generating the basin, started at least during the Messinian continuing through the Early Pliocene. The geometry and the style of deformation of the northward vergent structures, recognized in the study area, are coherent with other, coeval tectonic features of the NW portion of the Sicilian Fold and Thrust Belt, previously recognized by other Authors. A similar genesis and tectonic evolution can be therefore hypothesised for other Messinian-Pliocene basins, occurring in the same region. Basins generated in a transtensional tectonic framework are widely described in the international literature; here we describe an example of a sedimentary basin, generated at the core of syncline related to transpressional tectonics.