Revising the western Hyblean sedimentary succession: an update from field mapping and integrated stratigraphic analysis

In south-east Sicily, the succession characterizing the western sector of the Hyblean Plateau is mainly composed of carbonate sediments interbedded with volcanic rocks, ranging in age from Late Cretaceous to Quaternary. This succession has recorded the important climatic variations taking place during their formation. The field work of the geological sheet 648 (Ragusa), in the framework of the CARG Project, has provided the opportunity to carry out a thorough review of the successions cropping out in the area, whose last update dates back to the late ‘90s. The outcropping sedimentary succession is mainly represented by the Ragusa, Tellaro and Palazzolo Formations, ranging in age from Oligocene to late Miocene. The review we are currently carrying out consists of an accurate field mapping accompanied by a series of stratigraphic logs and sampling for a set of stratigraphic analysis, represented by integrated biostratigraphy (foraminifers and calcareous nannofossils), magnetostratigraphy and isotope stratigraphy. The results have allowed to provide detailed ages for the different traditional members of the Ragusa Formation (Leonardo and Irminio), highlighting the presence of intraformational unconformities. Another important topic is the geometric stratigraphic relationships between the Ragusa and the overlying Tellaro Formation, generally consisting of a gradual vertical transition, but affected by a lateral transition. A marked sharp angular unconformity, postdating lower Miocene tectonics, is also present in the Ragusa High area. The Oligo-Miocene litostratigraphic record helps to define a polyphase tectonic evolution, and a syn-sedimentary growth of structures along the Ragusa High hosting the Ragusa oil field.