Nature » Geology

Geological History 2

The platform of Friuli became the only source of carbonate debris, which temporarily accumulated at the edges of the scarp and then slided into the underlying basin. These were great landslides, capable of covering great distances and then stop against the scarp of the Trento Wrinkle. In this way the Vajont Limestone originated, gradually filling the Belluno basin and overlapping the Inferior Red Ammonite.
When the production of oolitic sands stopped, the Vajont calcarenite was replaced by thinner sediments which later will give origin to the Fonzaso Formation, grey-greenish flinty limestone which can be seen at Buse delle Vette.
At the end of the Jurassic period, a new slowing down of sedimentation due to the scarce production of debris by the Friuli platform and to the action of sea currents sweeping the seabed, led to the formation of the Inferior Red Ammonite, a very compact kind of rock, with evident nodules and fossils, which can be observed at Vette di Feltre, near Malghe di Erera and Campotorondo, in the Prabello Agnelezze group and in the south of Van de Zità. In the Cretaceous period (from 140 to 65 million years ago) the sea grew deeper and carbonate muds gave origin to the so-called Biancone, an ivory white rock with frequent nodules or stripes of grey or black flint, characterized by a typical concoid fracture (just as in glass) and a very thin grain. The Biancone forms the three top pyramids of Vette di Feltre, it emerges on the steep slopes at the foot of Sass de Mura, on the southern slope of Mt. Grave and Mt. Tre Pietre.