Carta geologica d'italia alla scala 1:50.000 e note illustrative del foglio 595_Palermo

Abstract

The Map Sheet 1:50.000 595 ”Palermo” includes marine and land areas of the topographic map sheet “Palermo”. The map sheet “Palermo” (Palermo Province) covers a part of the Sicily Fold and Thrust Belt (FTB) which has developed along the plate boundary between Africa and Europe in the Central Mediterranean. The Sicily FTB links the African Maghrebide to the Calabrian arc and Southern Apennines. The FTB and its submerged western and northern extensions are part- ly located between the Sardinia block and the Pelagian-Ionian sector, and partly beneath the central southern Tyrrhenian Sea. In this sector of the Mediterranean area, the main compressional move- ments, after the Paleogene Alpine orogeny, began with the latest Oligocene-Early Miocene counterclockwise rotation of Corsica-Sardinia, believed to represent a volcanic arc, and its collision with the African continental margin. Thrusting oc- curred in connection with the westward subduction of the Adriatic and Ionian lithosphere beneath the Corsica-Sardinia block. Today, a westward subduction is indicated by a North-dipping Benioff zone, as deep as 400 km, west of Calabria and the Apennines, and the related calc- alkaline volcanism in the Eolian Islands. Subduction and thrusting are contempo- raneous with a back arc-type extension in the Tyrrhenian Sea.186 LAND AREAS geomorphoLogy Three different sectors can be distinguished in Sheet 595: 1) the Palermo and Bagheria coastal plains, characterized by several poly- cyclic marine terraces organized in different orders; 2) the isolated carbonate reliefs of Monte Pellegrino and Monte Catalfano; 3) the internal Belmonte Mezzagno highlands and the Oreto and Eleuterio river valleys. The geomorphological evolution of the area has been controlled by strong down-cutting and dismantling processes that have produced both the erosion of thick volumes of mainly Tertiary terrigenous deposits and the exhumation of mainly Mesozoic carbonate rocks. Due to tectonic uplifting, these proces- ses are intensely developed on ”soft rocks “(Numidian Flysch clayey deposits), producing large river valleys with slopes affected by water erosion and surficial landslides (valleys of Fiume Oreto, Fiume Eleuterio and Fiume Milicia); they have, however, considerably slowed down along the blocks of more resistant rock (Mesozoic-Tertiary carbonate units), forming the wide Palermo Mountains. At the present-day, relict (planation surfaces and abandoned valleys), structural (fault/fault-line scarps) and karst (sinkholes and polje) forms occur in the highlan- ds. The geomorphological setting of the coastal areas has been influenced more by significant Quaternary extensional tectonics that originated the drowning of the northern sectors of the Sicilian chain in the Tyrrhenian Sea above which the marine deposition was deposited (Marsala synthem). The uplifting, involving also the lowered blocks, has resulted in the progressive retreat of the sea that gave origin to a succession of marine terraces, Ionian-Latest Pleistocene in age, and fi- nally the emersion of the present-day coastal depressions (Palermo and Bagheria plains). During the Upper Pleistocene to Holocene, the uplifting rates reached values generally lower than 0.1 m/ky. stratIgraphy The carbonate and terrigenous rock facies analysis and stratigraphy led to the recognition of large Paleozoic to Miocene sedimentary bodies pertaining to diffe- rent and separate crustal paleogeographic domains; the former, developed along the African passive continental margin and the adjacent Tethyan ocean. The “Tethyan” successions correspond to the deep clayey carbonate and vol- canoclastic rocks known to have been deposited in the Sicilide Domain. The pas- sive margin rock bodies are shallow water carbonates, deep water carbonates and 187 siliceous carbonates that were deposited in domains, lo