DOLOMITES - Annexes 2-8 - Provincia di Udine

NOMINATION OF THE DOLOMITES FOR INSCRIPTION ON THE WORLD NATURAL HERITAGE LIST UNESCO
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Age of geological units comprised in the Dolomites area. Timescale according to Gradstein et al. (2004)
Pre-Carboniferous Crystalline Basement
The oldest rock units of the Dolomites belong to the Paleozoic “Metamorphic Basement”, which
has good surface exposure in the Valsugana valley up through Agordo town, and into the Pusteria/
Pustertal valley. Paleozoic geologic units in the Dolomites are commonly complex metamorphic
rocks, made of albitic schists, porphyroids, and phyllites. These rocks were metamorphically altered
from greywackes (clay-rich sandstones), shales, siltstones, and rhyolites (volcanic rocks) respectively.
Paleozoic rock units in the Dolomites also extend from Carnia as part of the low-grade metamorphic
rocks of the Paleo-carnian belt, to the Lombardy. Deposition of metamorphosed sediments from the
Paleo-carnian belt occurred along the northern margin of Gondwana. These rocks have been identified
as Upper Ordovician and Devonian in age. Subsequently the Hercynian mountain chain was
built through a series of successive orogens during the Carboniferous and Permian Periods more than
280 million years ago. The extensive tectonic forces in this orogenesis (mountain building) compressed
and altered the sediments into metamorphic rocks. The final phase of the Hercynian orogenesis
involved widespread magmatic intrusion, which deformed the weak metamorphic strata before
cooling. Typical examples of these intrusive igneous rock bodies can be found in the western section
of the Dolomites where granites of Bressanone/Brixen extend from Val Pusteria/Pustertal nearly to
Vipiteno/Sterzing. But other well exposed examples exist in Lana, near Merano/Meran and farther
south where plutons (subsurface magma bodies) of Cima d’Asta and Doss del Sabion (Bosellini,
1996) can also be traced to the Hercynian orogenesis.
the Permian Period: dismantlement of the hercynian mountains
The dismantling of the Hercynian mountains began with the weathering and erosion of gained elevations
in subsequent periods. Eroded sediments were transported away by streams that etched
river valleys while filling others with sediment, altering the Hercynian landscape to one of hills, valleys
and fans of accumulated sediment (alluvial plains). Sand, gravel and detritus accumulated in the
deeper depressions forming what is now called the Ponte Gardena Conglomerate. The Ponte Gradena
Conglomerate preserves part of the Hercynian dismantling, through its unsorted, poorly stratified
sediments that indicate it was a high energy alluvial environment. Rocks from this section are made