Integrated stratigraphic approach to the study of the Neogene-Quaternary sedimentation and volcanism in the northern Hyblean Plateau (Sicily)

The investigated area lies along the northern margins of the Hyblean Plateau. Upper Miocene volcanoclastics and alkaline volcanics (GRASSO et alii, 1982), corresponding to the Sortino Synthem, comprise the pre-PlioQuaternary substrate in wide areas of the eastern sector of the map. The youngest volcanics consist of subaerial nephelinitic lavas (Catalicciardo Unit) with a K/Ar age of 5.46 +/-0.62 Ma. (BALOGH, pers. comm., 2000). Carbonates are, however, poorly represented in the underlying Monte Climiti and Carrubba Formations. Nevertheless, the Carlentini Formation is extensively developed as a cover beneath the Quaternary carbonates. This consists of subaerial lava and alkaline pyroclastics with coral bioherm intercalations of Tortonian age. A prolonged emergence episode separates the Miocene Catalicciardo Unit from the Pliocene, and is associated with deep subaerial incision of the earlier successions. This is the oldest of the first-order sequence boundaries used to define the region. A second, important first-order sequence boundary cuts deeply into the top of the Militello Formation tholeiitic volcanic complex (SCHMINCKE et alii, 1997), but is only clearly seen in the western sector. The Quaternary pale yellow calcarenites onlapped across this s.b. I boundary. The upper limit of these carbonates (Poggio Spica Synthem) is marked by another first-order sequence boundary which separates the Sicilian-Stage, greyish-blue clays from the underlying Poggio Spica (Emilian) calcarenites (PEDLEY & GRASSO, 2002). This can be clearly seen in marginal outcrops of the Lentini Graben. A major post-Sicilian regression (middle Pleistocene) is marked by extensive palaeosols containing important terrestrial vertebrate remains. Thin arkosic shallow marine Panchina carbonates of the Villasmundo Unit are only developed in the eastern sector above this s.b. I surface. The present land surface may be considered as the fifth and final sequence boundary. On the basis of these five first-order sequence boundaries, five main field-mapping units have been defined. The Emilian carbonates (Poggio Spica Synthem) have been singled out for special study as they have a ubiquitous distribution that enables a finer subdivision on the basis of second-order sequence boundaries and depositional mechanisms controlled by palaeobathymetry. Litostratigraphic units have been defined and named as follows: - the older formal and informal names have been maintained (e.g. Monte Climiti Formation, GRASSO et alii, 1982); - for units that have never been described and/or named in existing literature, the term unit, followed by the name of the locality where it is best exposed, has been adopted.