Geologic history of the Dolomites

The Dolomite mountains surrounding Cortina - and which create scenery unique in the world - are the result of the elevation and folding of large rock masses caused by tremendously powerful tectonic movements.
These phenomena ravaged an area which, about 234 million years ago, was the site of a warm sea, rather like the Caribbean today, dotted with rocks and small islands. One of these was in the Mount Cernera area, where gastropods, branchiopods, algae, sea anemones and characteristic ammonites have been found.

Subsequent volcanic eruptions created numerous islands.
Ongoing erosion produced large quantities of volcaniclastic deposits, dark rocks containing numerous plant fossils, a sign of the presence of tropical forests (230 million years ago).
Later on, evidence of a tropical sea (229 million years ago - Middle Triassic), rich in coral reef, was found in softer rocks such as marl and marl limestone: the so-called "San Cassiano Formation".

After the sea level dropped, large land areas emerged that drastically altered the appearance of the area (225 million years ago): the coral reefs disappeared and extensive flat sea-beds were formed; the sea facilitated the growth of large bivalves and many different species of fish, as well as the appearance of the first land reptiles.
The discovery, not only of animal fossils, but also of coal and amber, testifies to the existence of luxuriant forests.
Subsequently (224 million years ago - Middle Upper Triassic), the level of the sea rose again and, cyclically, covered the land, depositing carbon mud, the Principal Dolomite, that enveloped large lamellibranchs, called megalodonts.

Later on, tectonic upheavals caused the sea-bed to drop, slowly but relentlessly (210 million years ago - Late Triassic), creating tropical shoal conditions; the clear and rough waters favoured the formation of underwater sand dunes: the deposits consisted of carbon mud and sand. The climate became damper and colonies of branchiopods appeared in the sea.

Subsequently (185 million year ago - mid Jurassic), due to the sinking of the sea bottom, the bed dropped below one thousand metres.
The very strong ocean current did not favour the creation of large deposits. This was the marine environment most suited to large shells like ammonites. The few remaining deposits, coloured red and rich in ammonites, became known as Ammonite Red.
These were later covered by friable grey rock, only in some areas unaffected by subsequent tectonic upheavals: these are the so-called "Marls of Puez". Today these appear as hills of moderate height.

Following a period of strong earthquakes and elevation, an environment was created distinguished by a very broken coastline with high cliffs overlooking the sea and a series of valleys; fast-flowing rivers carried the debris down to the sea, thereby forming the beaches.
This way, the younger Dolomite rocks were born (25 million years ago - Tertiary), the so-called "Conglomerate of Mount Parei", consisting of rounded pebbles mixed with sands, algae, shells and sharks' teeth.