Geological history of Sardinia

Sardinia is largely formed by rocks of the Palaeozoic era or, to be more precise, the Cambric and Silurian eras. The Cambric lands are to be found in Inglesiente and Sulcis, made up of diverse sedimentary rock, metamorphosis belonging to three distinct series: an arenacea formation at its base, on the surface a complexity of clay scissions and an interpolation of chalkstone and dolomites; the site of zinc and silver lead deposits (territory of Iglesias).
During the Carboniferous period the corrugation of the earth provoked the rising of great magmata land masses hence the intrusion of granite. The solidification of the magma formed the foundations of the island and, furthermore, it was the transformation of the fragmented rock of a complex of scissions of clay, quartz, porphyry and others that cloaked the underlying granite. The granite intrusion has, without doubt, constituted the geological event that has primarily influenced the physical aspect of Sardinia; in fact it demonstrates the fundamental lines of its logography, its land and part of its existing mineral deposits. Consequently, it has also influenced the formations of the numerous great fractures similar to those of Iberia.
The lands of the mid- and superior-Palaeozoic are not widely represented. Until the beginning of the Mesozoic era, the ancient terrain of Sardinia was reduced to a vast plain of featureless land partially submerged in the Jurassic and Cretaceous seas, where it accumulated chalk and dolomite debris that eventually formed chalk banks and dolomites. The great alpine corrugation produced quakes so devastating that great fractures appeared in the ancient landmass, causing the fragmentation of the Palaeozoic and Mesozoic crusts in various areas, some being raised, some lowered and some even submerged.
Because of this, Sardinia has been likened to an unconnected mosaic. A series of fractures formed tectonic fissures that divided the island longitudinally into two unequal parts; one oriental, mountainous and continuous, the other occidental divided into smaller parts by minor fissures. During the mid-Miocene era the fissures were filled and progressively a new transgression caused the breaking of Sardinia and produced a great marine canal in which various deposits accumulated forming a series of sedimentary terrains stretching from Cagliari to Sassari.
 The tectonic movements caused other fractures that, overlaying those previous provoked great depressions, and the breaking away of the Isles of San Pietro and Sant'Antioco from Sardinia. From these fractures, during the last tertiary and quaternary abundant basaltic geysers have sprung up in Oristano, the valley of Tirso, Logudoro and the coastline. From the quaternary deposits, the canal that separated the oriental and occidental parts of the island was filled, forming fields. During the quaternary period Sardinia became similar in its aspect as we see today with only minor changes occurring in more recent times.
In substance, the island is constituted by an ancient continental landmass, isolated and partially dismembered from its alpine orogeny, which explains its low seismic activity.