Carta Geologica d'Italia alla scala 1:50.000 e note illustrative del foglio 594-585 PARTINICO-MONDELLO.

Abstract

The 594-585 ”Partinico-Mondello” Map Sheet 1:50.000 includes marine and land areas of the topographic map sheet “Partinico” and “Mondello”. The map sheet “Partinico-Mondello” (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 Maghrebides to the Calabrian arc and the Southern Apennines. The fTB and its submerged western and northern exten- sions are partly located between the Sardinia block and the Pelagian-Ionian sec- tor, and partly beneath the central southern Tyrrhenian Sea. In this sector of the Mediterranean area, the main compressional movements, after the Paleogene Alpine orogeny, began with the latest Oligocene-Early Mio- cene counterclockwise rotation of Corsica-Sardinia, believed to represent a volca- nic arc, and its collision with the African continental margin. Thrusting occurred 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. 237lAND AREAS geomorphology The geomorphological evolution of the studied area has been controlled by strong down-cutting and dismantling processes that have produced both the ero- sion of thick volumes of very recent terrigenous deposits and the exhumation of older rocks. Due to tectonic uplifting, these deepening processes are developed intensively on “soft rocks” (Numidian fysch clayey deposits), producing large river valleys whose slopes are affected by water erosion and surfcial landslides (Nocella and Oreto rivers); erosion has slowed down considerably along the more resistant Mesozoic-Tertiary carbonate rock units of the wide ranges of the Palermo Mountains. In the present-day, relicted planation surfaces and abandoned valleys, fault/fault-line scarps and karst “dolines” and “poljes” occur in the mountainous areas. On the other hand, the geomorphological setting of the coastal areas has been infuenced by important Quaternary extensional tectonics that were at the origin of the lowering of the northern sectors of the Sicilian chain submerged by the Tyrrhenian Sea and invaded by coastal marine depositions (Marsala synthem). Uplifting, involving also the subsided blocks, together with sea level variations, has led to the progressive withdrawal of the sea that originated a succession of marine terraces, Tarantian-Latest Pleistocene in age, followed by the emersion of the present-day coastal depressions (Partinico, Carini and Palermo plains). Du- ring the Upper Pleistocene to Holocene, the uplifting rates reach values between about 0.08 and 0,15 m/kyr. stratigraphy The carbonate and terrigenous rock facies analysis and stratigraphy has led to the reconaissance of large Paleozoic to Miocene sedimentary units pertaining to different crustal paleogeographic domains; the former developed along the Pela- gian (African) passive continental margin and the adjacent Tethyan Ocean. The “Tethyan” successions correspond to the deep sea, clayey carbonate and volcanoclastic rocks known to have been deposited in the Sicilide Domain. The passive continental margin, rock units are Meso-Cenozoic shallow water carbo- nates, deep water carbonates and siliceous rocks that were deposited in some domains, locally known as Panormide, Trapanese and Imerese. The terrigenous evaporitic and clastic-carbonate rocks, Miocene to Pleistocene in age, formed during the foredeep evolution of the Sicilian fTB. A detailed stratigraphy of the rock-successions is summarized in