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Pietraroja Geopaleontological Park

Geologycal short account

The present structure of southern Apennine results from a lot of streamings, crossing that are events which happened since Pleistocene (1,7 million years ago) to now and which are still happening.

Till Pleistocene the big mountain chains which made the framework of Apennine range and particularly the Matese carbonatic rocks, were in the making in a sedimentary basin which filled up the present Mediteraneum sea (Tetide basin). Actually in the upper Triassic (210-230 million years ago) the "pangea" breaking started.

Era_1

Afterwards owing to the spreading or stretching movements which occurred in Jurassic (150 million years ago), the separation among the many continental plates of Pangea and Tetide making between Europe and Africa started.

Era_2

Inverting pushes in Eocene (40 million years ago) owing to the pressing pushes between Africa and Europe caused "Tetide" closing.

Era_3

The pressing pushes lasted in Miocene (20 million years ago) and made the carbonatic piles broke in big blocks in the former sedimentary basin causing the Apennine orogenesis.

Era_4

Apennine chain started rising in Pliocene after the pressing pushes between Africa and Europe came to an end.

Era_5

Starting from development of Apennine chain we may suppose that the calcareous massifs grew up in a sedimentary basin where the carbonatic salts set up well-balanced calcareous piles which grew and grew. That balance lasted perhaps 150 million years and if we consider that carbonatic sediments settled down by a medium speed of about 2,5 cm each one thousand year, a pile of some thousands metres of calcareous sediments was made up and they produced the calcareous rock. Only in Cretaceous (70-140 million years ago) there were events which changed that dynamic balance and which are linked with the movement which caused the opening of southern Atlantic and with the pressing pushes between Africa and Europe. In spite of these risings the fossils give evidence of a natural and alive environment with lukewarm oxygenated waters where calcareous mud and remains were stored in order to make up a cliff: the surroundings might have been very similar to the present Australian Coral Reef or to the Bahamas Islands.

In the basin where the present Pietraroja and other places (Castellammare di Stabia, Carso triestino etc) were making, the natural conditions, which made Pietraroja a geopalaeontological feature, occurred just during the Cretaceous.

Structurally it appears as a ‘monoclinale’ lightly sloping down to east bordered by ‘strike fault’ which isolate it between Titerno river and Torbido stream.

Cusano is situated near Pietraroja and in the south-east; in Titerno lower valley there is Cigno mountain. Among the three ‘monoclinali’ we can notice palaeontological similarities even for calcareous stones and ‘ittioliti’ (fishstones) besides the obvious structural similarities.

Pietraroja area might have been like to a low lagoon since by analysing mineralogical compounds, calcareous stones make up the upper layer of all its typical geological structure:

They were made up in smooth water surroundings, on the contrary the different geological makings show that they come from quite different surroundings with slightly upset waters.

Calcareous and ‘ittioliti’ microcristallinicalcite’is a proof of rather quick sedimentary surroundings but poorly active. The amount of fossil in calcareous fish stones’ittioliti’ may come from the same making surroundings. As matter of fact, either the investigation about microfossils (radiolari etc…) or about macrofossils (shellfishes, anphibians, reptiles, etc…) show lagoon surroundings which came irregularly in touch with the open sea.

Perhaps the open sea and lagoon came in touch with each other when tides and storms happened. There were frequent dryings up and fresh waters flows, probably coming from the emerged lands not far from the lagoon. We suppose that the emerged lands were nearby since there are a few pollens in the same calcareous stones.

 

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Con il contributo dell'Ordine dei Geologi della Campania

       
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