224 million years ago, during the Norian stage, a general increase in sea level
resulted in land areas being periodically covered by the sea (tidal plains), as
is the case today of a number of islands belonging to the Bahamas archipelago.
In this environment, simplified in the picture on the right, the Main Dolomite
deposits began to form. A typical feature of Main Dolomite is its cyclic nature,
which can be seen by observing the rock faces. These consist of very regular strata,
indicative of events that occur cyclically. By carefully observing each single
stratum, we can see that these, in turn, consist of two parts: one is densely
laminated and corresponds to carpets of fossilised algae, the other is thicker
and consists of calcareous mud transformed into rock which contains the internal
models of bivalves, the megalodonts. The cycle was repeated dozens and dozens of
times due to a lucky concurrence of circumstances, among which a slow, but
continuous lowering of the sea-bed (subsidence). By offsetting the depositing
of mud and the growth of the carpets of algae, this resulted in the water
remaining shallow throughout the region.
The repetition of these cycles for about ten million years produced an accumulation of 1000 metres of deposits that today form the magnificent rock faces around Cortina d'Ampezzo.