Sedimentary and tectonic evolution of the eastern Hyblean Plateau (southeastern Sicily) during late Cretaceous to Quaternary time

Abstract

Two palaeogeographic domains have been distinguished in the Cretaceous-Quaternary sequences which crop out in the Hyblean region of southeastern Sicily. In the northeast shallow-water algal-bryozoan calcarenites of Oligocene-Miocene age overlie either Cretaceous rudist limestones or volcanics. Further to the northeast, the stratigraphic gap increases as the Miocene limestone thins, and in the A.G.I.P. well Catania 10, Plio-Pleistocene sediments and volcanics directly overlie Upper Jurassic rocks. In the southwestern part of the Hyblean Plateau pelagic sediments occupy the Cretaceous-Miocene interval. They were deposited in a shallow basin dipping gently towards the southwest. The transition between the two zones is marked by much evidence of synsedimentary tectonic activity, such as widespread slumping and the development of megabreccias composed of Cretaceous and Eocene blocks. The palaeogeographic picture is one of carbonate reefs and volcanic seamounts developing in the Upper Cretaceous. They formed platforms, fault bounded to the west and southwest, from which were derived the detrital sediments found in the basin, and occasional spectacular gravity slides. In present-day terms the structural high probably corresponds to the northeastern margin of the Hyblean Plateau and in part to the (Siracusa) Syracuse-Malta Escarpment. The pattern is little changed in the Upper Miocene with volcanoclastics of phreatomagmatic origin, intercalated with coral bioherms, overlying algal-bryozoan calcarenites. Upper Tortonian-Lower Messinian limestones with a restricted fauna indicate a shallow-water environment which grades up into continental conditions. In the eastern Hyblean Plateau, the Tertiary sequence is capped by Pliocene submarine to subaerial mafic lava flows. Lower Pleistocene sediments consist of biocalcarenites and clays which fill deep graben delimited by Plio-Pleistocene faults, the inshore continuation of the Malta-Syracuse Escarpment system of faults. From a tectonic standpoint the Hyblean region, a gently deformed segment of the African continental margin, acted as a foreland during Tertiary times. A Cretaceous-Eocene tectonic phase was responsible for the palaeogeographic pattern which existed during most of the Cenozoic. The present pattern is the result of three main tectonic phases following the regional Upper Miocene uplift, of Early-Middle Pliocene, Plio-Pleistocene and middle Pleistocene-Recent age which influenced the tectonic evolution of the present Ionian coast and the Malta-Syracuse Escarpment.