GEOLOGY
Different lithologies characterize geologically the territory of Carbonia giving the landscape distinctive and unique features in Sardinia.
Hills of modest height form its orography; Monte S. Michele Arenas is the highest hill with 492 metres above sea level.
The area presents rocks of various petrographic and structural features whose age, on the whole, covers more than 500 million years. These rocks witness the geologic events that followed one another in Sardinia; these events are well represented in the region of Sulcis, with the richness of its fossils perfectly preserved up today.
The north and east areas of the town are characterized by Paleozoic rocks set out as a semicircle that bounds the basin of Carbonia: the lithologies are represented by limestones and sandstones often very fossiliferous. They go back to the Cambrian period (570 million years). The fossils commonly found are the "Archeocyata" (an organism with features of transition between the corals and the sponges) and the Trilobita (crustaceans): paleontologists and scholars come from all over the world to search for them because they are the most ancient fossils in Europe.
Archeociatine
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Trilobita
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The landscape is very particular, characterized on the one side by the lack of superficial water and on the other by an abundance of Karst cavities esteemed very important from a morphological and mineralogical point of view. It is especially notable the cave called "Corona sa Craba" where peculiar concretions of the rare blue barite can be found.
The landscape originated from the carbonate rocks appears with reliefs nearly always covered with the Mediterranean maquis; they are characterized by very irregular surfaces, rough and uneven reliefs in contrast with the remaining areas of the municipal territory.
Cave of Beghe Forru
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The west and south areas of the town present volcanic rocks that go back to the Tertiary period (Oligo-Miocene, 26 million years); they originated during the phase of the anticlockwise rotation of Sardinia and Corsica (after the detaching from the French and Spanish coasts), phase that saw the present displacement of the two islands. These rocks belong to the Cenozoic formations that are typical of Sulcis, with basalts and andesites at the bottom and above ignimbrite rocks (their age goes from 28 to 11 million years) for 500 metres of thickness.
This part of the territory is characterized as well by the presence of numerous small cavities that contrarily to the rocks of Karst origin, are contemporaneous to the formation of the rocks in which they are found. On these rocks the atmospheric elements have created, during some millions years, original shapes called "Tafoni".
Tafoni (Monte Crobu)
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Under these volcanic rocks, with some outcrops in the surroundings of Bacu Abis, there is the most important Italian coal-field. The coal seams that go back to the Eocene (54 million years) were noticed for the first time by Alberto La Marmora in 1857.
Working mine (Seruci)
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Fossil palms and "foraminifera" ("Alveoloine" and "Miliolidi") can be found in the lignitiferous basin, composed of calcareous and clayey layers and thick levels of coal.
The Quaternary period is represented both by sediments of sea origin, characterized by a fossil fauna consisting of molluscs (Gastropada) typical of warm seas and by sediments of continental origin. The alluvia, situated in the west of the town, refer to this same period and were constituted by the crumbling of the preceding geological Formations that outcropped in the territory.
Situated on the border between the municipal territory of Carbonia and Gonnesa, the peculiar fossil dunes of Fontana Morimenta go back to the interglacial Riss-Wurm stage; inside them important fossil remains of a dwarf Elephant (Elephas melitensis, of only 1.40 metres of height) were found. In these same dunes there are also the remains of Cervidae (Megaceros Cretensis) and various kinds of reptiles.
