Italy Tectonics and Genesis Part I

By | February 16, 2022

According to IAMHIGHER.COM, Italy is a young land; on the contrary of Iberia, generated by a primordial nucleus that grew larger through the geological ages by successive additions, it arose mainly thanks to the most recent of the great orogenetic corrugations, the Alpine; the remains of the most ancient structures are, as far as the extension is concerned, subordinate and peripheral by position.

The orogeny of the Paleozoic era (see Europe: Geology) had raised a land to the west of the current peninsula, which later disappeared almost completely, of which Sardinia, Corsica, and the Maures group with the Hyères islands in the Mediterranean are wrecks. Provence. Further to N., where the Alps later rose, other lands connected the now mentioned with the Ercinidi of Mesoeuropa.

The general paleozoic substratum of Sardinia belongs to this ancient Hercynian country, where the sediments of the Middle Cambrian arched first, then covered by the Ordovician transgression and upset all immediately after by the Caledonian orogeny, which produced strongly constipated folds and perhaps also ruts ( Iglesiente and Nurra). The rest of the Paleozoic was deposited around the land thus arisen, until the Hercynian folding in the Upper Carbonic intervened, followed by granite intrusions and porphyry effusions, widely developed in eastern Sardinia and western Corsica. The granites of Sardinia are accompanied by gneiss, mica schists and phyllites that Lamarmora already judged ancient Paleozoic metamorphic.

Massive masses of ancient soils mostly in the form of crystalline schists are found in the Alps and in the southern Apennines, which, with less certainty than Sardinia and Corsica, are considered to be the remains of Hercinids locked in the alpine folds. The least controversial, within the limits of the Italian region, are the Argentera, Mont Blanc, the Gotthard and the Calabro-Peloritano massif, considered indigenous. However, there is no evidence of any of these that at the end of the Palaeozoic they were wholly or partially emerged. Thus, the true extent of the earth formed in that time and duration with not too variable limits remains unknown throughout the Mesozoic. On one side of it there was a sedimented continental sea with  Germanic facies  ; on the other, the Tethys with  facies  depositsalpine.

In the Mesozoic era, it was of relative calm, epeirogenesis prevailed. We find evidence of this in Sardinia, where strips of Autunian (Permian), of Mesozoic with  Germanic facies  , from the Trias to the Cretaceous, and of Eocene still rest with penet horizontality on the Hercynian plateau in the same way as in Calabria and in the Peloritani the Mesozoic. The eruptive activity did not stop. This is proven by the eruptions of “Pietra Verde” from Trias in the Eastern Alps, and various eruptions of Predazzo in Trentino, the very extensive prasinites, euphotids and serpentines of the calcescists of Alto Adige, Grisons and the Western Alps, the basalts from the Jura onwards of Sicily; the Apennine ophiolites.

At the end of the Eocene, the irresistible thrusts of Alpine dastrophism lift the sediments of the Tethys into grandiose folds and overturn them against the Hercynian massifs so that extensive slopes of carriageway override them.

Sardinia alone remains immune, but under the enormous pressure it breaks from N. to S. giving rise to a median pit (Campidano, Logudoro) which will later be filled by sediments and eruptions, which, starting with the production of the pit , will persist until the Pliocene. The shining shales with ophiolites of Capo Còrso and those to the east of the S. Fiorenzo-Corte-Ghisoni line are raised against the Corsican granites from the eastern band in folds of a distinctly alpine character.

The major work of the uplift was the Alpine System with the characteristic course of the tectonic lines that directed almost E.-O. in the eastern sector, they curve in the western part in a vast semicircle that seems to join up with the Apennines to surround the Padanian gulf. Curvature attributed to the presence of the three presumed autochthonous Hercynian massifs of Mont Blanc, Belledonne-Pelvoux, Argentera, against which the folds would have adapted by bending. It is admitted that the system consists of two large units: the Alpids properly called N., with tormented tectonics of overlapping strata and intense metamorphism, against which the Dinarids composed mainly of secondary layers and of the ancient tertiary , a  facies normal, with simpler structure than ordinary folds and fracture dislocations. The line of separation between Alpids and Dinarids, not evident from any morphological accidentality, would start from Ivrea, would pass to N. dell’Adamello and would continue towards E. (Alpine-Dinaric line or Tonale or Insubric line; see Alps: Geology ).

In the Miocene the Apennines already took shape from Liguria to Sicily, at first not yet continuous, but interrupted by arms of the sea, of which the most important crossed it from the NNE. to SSO. between Umbria and Abruzzo. To the north of this channel runs, from Liguria and Piedmont to Umbria, the wide axial bundle of land mainly tertiary (clayey schists and sandstones), with a structural trend from master to sirocco (Liguridi), flanked on the west side by the Spezia downwards, from the Tuscan Preappennino (Apuane and Catena Metallifera) still an archipelago, with prevailing Paleozoic and Mesozoic soils and tectonic lines north from NW. to SE. but which around noon become N.-S. in the Grosseto area (Toscanidi).

Italy Tectonics 1