Paleozoic (541-251 million years ago) The oldest rocks in Italy may include oceanic crust subducted during the
Caledonian orogeny and 440 million year old
Ordovician granites. Only detrital
zircons in the Alps dates to the
Precambrian. These granites are located offshore of
Venice, found in the Agip Assunta well and deformed, transforming into
orthogneiss during the
Hercynian orogeny. Overall, Italian
Paleozoic rocks commonly show evidence of the Hercynian orogeny in the Alps,
Sardinia, the
Apuan Alps of Tuscany, and the
Peloritani mountains of Sicily and Calabria. The Hercynian orogeny produced a large thrust belt, thickened the crust and led to polyphaser metamorphism yielding rocks such as
gneiss,
phyllite and
amphibolite.
Metamorphic facies range from high-pressure
kyanite to low-pressure
andalusite. The Western Alps at
Mont Blanc and
Monte Rosa, the
Southern Alps at Braveno,
Brixen,
Cima d'Asta, Doss del Sabion and the
Barbagia and
Gallura granites in Sardinia are all examples of
Carboniferous and
Permian granite
pluton and
batholith intrusions.
Ignimbrite eruptions had an important role at the same time in forming parts of the central Southern Alps. Sedimentary rocks from before the Permian have remained intact and unmetamorphosed (or only having experienced low-grade metamorphism) in the Paleocarnian
charn of the eastern Southern Alps. The
metamorphic grade increases to the west, reaching
amphibolite grade in the Orobic Alps and
granulite grade in the
Ivrea-
Verbano Zone. Most of the basement rocks in the
Dolomites are
phyllite or gneiss at
greenschist grade. Within the Dioritic-Kinzigitic unit,
biotite and
sillimanite-rich gneiss outcrop in Calabria. peridotite from the
Ivrea zone At the same time in the Permian and Carboniferous, the opening of the west branch of the
Tethys Ocean reoriented sections of Italy atop the
Adriatic Plate and created the Ligure-Piemontese ocean basin, leading to widespread deposition of carbonates, evaporites and
red beds. Units such as the Valgardena Sandstone emplaced during a westward marine transgression in areas later uplifted as the Alps. These sandstones were succeeded by
sabkha, the lagoonal Bellerophon Formation, volcanic rocks, the
Werfen Formation and Servino Formation.
Mesozoic (251-66 million years ago) Even in the 19th century, geologists recognized
Ladinian and
Carnian age
carbonate platforms in the
Dolomites that likely formed as
coral atolls. Throughout the early
Triassic, the
Zorzino Limestone, Rhaetian Choncodon Dolomite,
Riva di Solto Shale and Zu Limestone filled the Lombard Basin. Up to two kilometers of carbonates assembled in the late Triassic as the
Dolomia Principale. Meanwhile, the Lagonegro Basin accumulated limestone, chert and marl into the
Jurassic. Complex tectonics produced
horst and graben features and some lowlands deposited evaporites, such as the Burano Anhydrite—now a significant unit in the
Apennine Mountains. Jurassic tectonic conditions differed somewhat from the Triassic, resulting in new basin formation and a carbonate depositional environment akin to the current day Florida-Bahamas platform. Southern Alps basins such as the Lombard Basin and the Belluno Basin gathered marl and limestone, while
turbidite and nodular limestone was more common in the Vajont Limestone, Fonzaso Formation and Selcifero Lombardo. In addition to wide shelf environments like the Bahamas, seamounts like the Trento Swell or the Sicilian Iblean and Saccense zones, some basins such as the Piemontese Basin, the Lagonegro Basin and the Ligurian-western Tuscan Ligure Basin were situated above
ophiolite and ended up with abundant
radiolarite fossils in limestone. rock of Jurassic age from Lombardy During the
Cretaceous, global high sea levels and local tectonic conditions produced a greater share of basins than platform environments (although the Campano-Lucana,
Friuli,
Apulia and Latium-Abruzzi platforms persisted). More
pelagic, open water sediments like marl joined
breccia and underwater debris flows. Triassic conditions persisted in only one location in Sardinia where up to one kilometer of carbonates finished depositing in the Cretaceous, atop deformed Cambrian-Carboniferous
metamorphic basement rock. Changing interaction between the
European Plate and the Adriatic Plate resulted in tectonic compression along the Adriatic Plate's northern margin, kicking off the formation of the Alps and the Apennines. In the late Cretaceous, foredeeps filled with
flysch and
molasse sediments shed off the rising mountains. Examples include the Bergamo Flysch within the Lombard Basin of the Southern Alps. The Mesozoic was largely quiescent in terms of
magmatism, but some igneous activity did take place. Pietra Verde sandstones from the
Ladinian in the Southern Alps contain
calc-alkaline rock while granite,
shoshonite and
monzonite intruded the Dolomites region into the
Carnian. In fact, subsurface rocks in the
Po Valley, the Lagonegro Basin, west
Trentino, the Venetian foothills, Sicily, Lombary and the northern Apennines show signs of
volcaniclastic sediments and
pillow lava from the time period. Although the oceanic crust of the Tethys Ocean has been recycled into the mantle, sections of it remain as ophiolite with
peridotite,
gabbro,
prasinite,
serpentinite and pillow lava of Jurassic to Cretaceous age in
Liguria,
Tuscany,
Val d'Aosta and
Piemonte. Petrological research indicates that
ophiolites in the Alps are metamorphosed, while those in the Apennines are not. The Ragusa Basin in the Iblean Plateau of Sicily had magmatism in the Jurassic, together with the Trapanese Basin, followed by Cretaceous activity in the
Syracuse area.
Cenozoic (66 million years ago-present) , southeast Italy sediments of Pliocene–Pleistocene age in
Atri, Abruzzo During the
Paleocene, the Eurasia-Africa convergent margin driving the Alpine orogeny accompanied the closure of Alpine Tethys ocean basin. As a result, magmatism emplaced in the Periadriatic region lasting into the
Oligocene:
Basalt dyke intrusions (Dolomites) and volcaniclastic rocks (
Lessini Mountains), alongside various
batholiths (acid rocks like
trachyte,
tonalite,
syenite,...) can be found. The Alpine tectonics affected the magmatic bodies during the uplift: the Insubric Lineament dividing the Southern Alps, for example, sheared the Bregaglia batholith. Sedimentary processes were affected from the orogeny in form of turbiditic deposits accumulating in nearby basins. In the North-east, Eocene age flysch shed off the
Dinaric Alps can be found in the present-day foothills of Friuli region, while shallow water deposition (shale and carbonates) persisted in areas further away from the thrust belt. Paleontological evidences include the fish fossils of
Bolca quarry ( close to
Verona). In the
Eocene, the Apennine orogeny started evolving independently from the Alps as a result of a new west-dipping subduction and continental collision between Corsica-Sardinia block and Adria microplate. Following the eastward migrating subduction zone, sediments of the Adriatic margin and Ionian Basin accreted onto the Apennine area as a tectonic nappe stacking from the west. As the Adria microplate migrated to the northeast with an anti-clockwise rotation, Apennine foredeeps migrated to the east with continued flysch deposition in younging basins from west to east (Macigno, Cervarola, Marnoso-Arenacea...). In the Northern Apennines, the Liguride units (oceanic sediments and ophiolites) were deformed and later (Oligo-Miocene) thrusted upon Tuscan and Umbria-Marche Units (passive margin pelagic basins). In Central-Southern Italy, carbonate platforms (Lazio-Abruzzi, Apulia...) persisted alongside turbiditic basins (Lagonegro...) up until late Miocene. In the Southern Apennines, like the Liguride Units, flysch units with
ophiolite were incorporated in the orogenic arc (Cilento Flysch, Flysch Rosso and Frido Flysch). The deformational history of these units is recorded by the alternating shale, sandstone and conglomerate. In Sicily the Maghreb-related Numidian Flysch from Miocene contains quartz and
arenite sands likely deposited by a river delta from Africa and overlain by the coarser Goroglione Flysch. During the
Miocene, the ongoing uplift affected Alps as well as the Paleo-Apenninic chain and backarc to foredeep basins continued developing. In the Southern Alps, Gonfolite Lombarda and Molassa Bellunese flysch started filling the Po basin. Around the Apennines and Sicily, late Miocene evaporites were left by the
Messinian salinity crisis (for example, Gessosso-Solfifera Formation). The opening of backarc basins like the Thyrrenian Sea caused the Calabro-Peloritan block to be separated from Sardinia, moving further south-east and finally included in the southern apenninic arc. Uplift continues today and since the Pleistocene, Calabrian sedimentary rocks have uplifted more than .
Pliocene-Quaternary volcanism in Italy occurred with the onset of
extensional tectonics of backarc basins like the
Tyrrhenian Sea: seamounts and island arc volcanism developed as well as on-land magmatism in Tuscany, Lazio and Campania, often aligned with NE-SW trend followed by the main normal faults of the Apenninic chain. For example, the islands of
Elba is an exhumed granitic batholith over thinned continental crust, while
Stromboli is a stratovolcano originated atop newly formed oceanic crust. The most recent volcanic island is
Ferdinandea near Sicily, once emerged with the 1891 offshore eruption but quickly eroded below the water, remaining as the
Graham Bank. Historically active volcanoes are sometimes very explosive like
Vesuvius, while others like
Mount Etna tend toward less explosive basaltic eruptions. ==Natural resource geology==