DOLOMITES - Annexes 2-8 - Provincia di Udine

NOMINATION OF THE DOLOMITES FOR INSCRIPTION ON THE WORLD NATURAL HERITAGE LIST UNESCO
70
the emipelagic deposits of Biancone and Scaglia Rossa
With the end of the Jurassic and the beginning of the Cretaceous, around 150 million years ago, the
entire Dolomites area was affected by the deposition of calcareous mud of planktonic origin, typically
whitish in color (Biancone Formation). During the Cretaceous, while the western Dolomite areas
were still in deep seas, further north, the collision between Africa and Europe caused rocky islands
to emerge in the area corresponding to the present-day Switzerland and Austria. From this emerged
land, subjected to the erosive action of weathering processes, great quantities of argillaceous sediments
invaded the “dolomitic” water and were deposited on the seafloor.
At those times, in the area of Giudicarie Valley a real tectonic threshold was active (the Giudicarie
Paleoline), that prevented propagation of these sediments southwards. With the passing of time the
effects of the Alpine compression felt more violent. Along the Giudicarie belt a series of folds rose
up with a NE-SW orientation, separated by crests of varying depths. This paleogeographic situation
prevented the ocean currents from oxygenating the entire seafloor and sediments very rich in
organic substances accumulated in restricted areas. This is the Scaglia Variegata, a typical succession
of gray, greenish and whitish micritic limestones, usually bioturbated (Chondrites), with radiolarians
and foraminifers, well-stratified (5-15 cm) and sometimes chert-containing (nodules and beds
of black chert), alternating with grey-greenish, black and reddish marls, sometimes bituminous and
very thinly layered.
Tipical landscape with Puez Marls (Col da la Sonè).
In the Adige Valley, south of the Valsugana Line and in the Dolomites Friulane, the sediments of
this time were widespread, north of the Valsugana and in the rest of the Dolomites are those preserved
only in the area of the Puez and in the Gardenaccia (Puez Marls). This unit is sporadically
found in the area of the Altopiani Ampezzani, where it is frequently involved in the so-called ‘peak
overthrusts’, and comprises a rather monotonous alternation of siltous marly limestones, gray-green
(very occasionally reddish) marls and rare green and blue argillites. The Puez Marls contains abundant
macrofauna with echinoderms, bivalves and, above all, ammonites (the hetermorphic ammo-