Italy Geopaleontological Description Part 1
According to Collegetoppicks, Italy examined from the geological point of view presents such a quantity of land, both chronologically and lithologically considered, such a variety and often complication of tectonic phenomena, which is not found elsewhere on Earth in a relatively small area. However, due to the relative recent formation of Italy, the archaic rocks do not emerge. In fact, the more intensely crystalline soils, such as gneisses, micascists, granites and similar rocks, which appear widely in the Western Alps and in the Calabrian region and which for a long time were attributed to the archaic or archeozoic era , now instead we tend to consider them mainly as metamorphic representatives of paleozoic soils.
However, it does not seem unlikely that the deepest part of such gneissic formations could still refer to the Higher Archaic or Proterozoic.
The Paleozoic or primary era is represented, however, in Italy in almost all its periods, but with very different facies . First of all, it should be noted that a good part of the gneissic, micascistose, granite and similar formations, eminently crystalline, which develop quite extensively in the Alps, especially in the West and in the heart of the Central ones, as well as in the Calabrian-Sicilian region, and in central Sardinia. northern, are referable to the Paleozoic, without however being able to generally specify the age due to the lack of fossils, essentially due to the intense metamorphism; their upper part is attributable to the Permo – carbonic for carbonaceous traces, but in their lower part there is so far no possibility of determining safe subdivisions.
Apart from these metamorphic formations of the Paleozoic, the following periods are represented in Italy:
Cambric . – It appears essentially in southern Sardinia (Iglesiente) for about a thousand square kilometers, with a thickness of several hundred meters.
The series is represented, from bottom to top, by philladic schists, calcescists and limestones (the so-called metalliferous limestone , including part of the well-known mineral deposits of Sardinia); sandstone and sandstone schists, here and there again with limestone. This series is often rich in various fossils, especially Trilobites ( Paradoxides , Conocoryphe , etc.), Lingules, Archaeociates, Bilobites, etc.
Siluric . – It appears typical especially in the Eastern Alps and in Sardinia.
In the Eastern Alps the series is formed overall, from bottom to top, by: brownish or varicolored schists and calcescists with many Brachiopods ( Orthis , Strophonema , etc.), Cystoids, etc .; sometimes very rich brownish schists in various forms of Graptolites; brownish limestones, with a power of up to 300-400 meters, with frequent and varied Orthoceras , Cyrtoceras , Cardiola , Rhynchonella , some Trilobite, various Corallarî, etc. At the base of the series constituting the Apuan Alps there is some outcrop of limestone and mica schists with Orthoceras, which appear to be attributable to the Silurico; doubts are the analogous references of certain schists on the island of Elba. On the other hand, in Sardinia the siluric series is very well constituted, from bottom to top: by breccias or conglomerates; from a powerful formation of clayey or arenaceous, brownish schists, with several Trilobites ( Asaphus , Trinucleus , Dalmanites ), Phyllocarids, various Brachiopods ( Lingula , Orthis , Strophonema , Leptaena , etc.), Crinoidei, Cistoidei, etc .; by various gray-brown clayey scholars with different forms of Graptolites; from limestones with numerous Orthoceras and Cyrtoceras , several Mollusks (Cardiola , Pleurotomaria , etc.), Ostracodi, etc.
Devonico . – It was well recognized in the Eastern Alps, where powerful masses of grayish limestone (even a thousand meters thick) belong to it, mostly reef-like, with hundreds of fossil species, with a predominance now of the Corallarî, now of the Brachiopods , now of the Cephalopods; frequent are the genera: Pleurotomaria , Euomphalus , Murchisonia , Loxonema , Clymenia , Posidonomya , Stringocephalus , Productella , Rhynchonella , Spirifer , Atrypa , Stromatopora , Pentamerus , Syringopora , Cyathophyllum , Alveolites . In Sardinia special limestones in Clymenia belong to the Upper Devonico .
Carbonic . – Although they do not generally include real industrial hard coal, the soils of this period are very developed in Italy. In addition to the metamorphic facies (different crystalline schists, here and there graphitosis or even anthracitiferous) that develops especially in the Western Alps and in some points of the peninsula, the Carbonic is represented by brown schists of various kinds, sometimes richly phyllite with Sphenopteris , Pecopteris , Cordaites , Calamites , Sigillaria , Lepidodendron , Asterophyllites , Annularia , Lepidophyllum, and in the Eastern Alps from schists, sandstones and brown limestones, sometimes arenaceous to Fusuline, Coralli, Fenestelle, Crinoids, Bryozoans, Brachiopods ( Spirifer , Productus , Chonetes ), Mollusks ( Conocardium , Bellerophon , Euomphalus ).
Part of the various eruptive rocks (porphyry, porphyrites, diabase) and perhaps some plutonic ones (granite and the like), which are sometimes found associated with the schist masses of that period or of more ancient soils, is also referable to Carbonic.
The carbonic soils, often very powerful and often with passage to the metamorphic facies , develop in the Alps, they also reappear in several points of Tuscany, the island of Elba and Sardinia, where they are sometimes anthracite.
Permic . – The soils belonging to this period are in Italy, as often elsewhere, so connected with those of the Carbonic and analogous to them for lithological characteristics, that it would be logical to combine them in a single Permo – Carbonic (or Anthracolitic) whole.