Geological history

Geological history
(photo by: PN Dolomiti Bellunesi)

In the Upper Trias (230-210 million years ago) the region was situated in the tropical area and its climate was similar to the current climate of the Caribbean. In a boundless and shallow coastal sea characterized by tidal fluctuations, the sediments which later on will give origin to the deposit originating the Dolomia Principale formation. Dolomia Principale is the most widespread rock in the Park. It forms the socle of great part of the Park mountains. The abrupt and almost inaccessible Monti del Sole are almost exclusively set in this formation.
Subsequently, after stretching movements of the earth’s crust, a much deeper sea drill, the Belluno basin, developed between two Platforms or Wrinkles (Trentino and Friuli). The Park area found itself in the transitional area between the basin of Belluno and the Ruga Trentina (wrinkle), where different sedimentary environments could be found.

In the western area, the carbonate muds deposited, which later will give origin to the formation of the Grey Limestones (more or less rich in dolomia and sometimes rich in fossils) while, in the Jurassic period (170 million years ago), the collapse of the Trento platform took place and a long pause in the sedimentation process favored the accumulation of rests of marine organisms. In this way, the Inferior Red Ammonite originated, a reddish limestone characterized by evident nodules.

The basin of Belluno was interested by calcareous formations rich in clayey or flinty components (Soverzene and Igne Formations).

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 basin of Belluno 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.

The most recent formation outcropping within the Park is the Scaglia Rossa (Upper Cretaceous). This is a brick red or grey-rosy marly limestone outcropping in the Park near the Mountain Hut Boz, on Mt. Brendol and Talvena: the toponyms “Le Rosse di Erera” or “Le Rosse di Vescovà”, “Val dei Ross” clearly indicate this kind of rock.
Scaglia Rossa originates from muds deposited in a deep-sea environment, but it contains a considerable quantity of clay, with many traces of fossils left by big worms sieving the seabed.
The presence of clay denotes that there is debris coming from emerged areas after the first stages of the Alpine orogenesis. The uprising of Dolomiti Bellunesi mainly occurred in the last ten million years within the more general process of the earth’s crust compression, which gave rise to the Alpine chain and intensely deformed, refolded, fractured and overlapped the rock layers.
In some areas, this process led to the formation of spectacular “thrusts” of older rocks over more recent ones. Dolomiti Bellunesi chain structurally corresponds to a big anticlinal “wave” (Coppolo-Pelf anticline), running from Vette di Feltre to Schiara.