DOLOMITES - Annexes 2-8 - Provincia di Udine

NOMINATION OF THE DOLOMITES FOR INSCRIPTION ON THE WORLD NATURAL HERITAGE LIST UNESCO
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the Calcari Grigi and the definition of an early-drowning carbonate platform
Towards the end of the Triassic, the paleogeographic scenario of the Dolomite area and of the entire
southern Alpine region changed in a radical way. The phase of differential subsidence and the establishment
of a distensive regime ascribable to the formation of the passive margin are characterized
by paleogeographic and paleostructural elements that are elongated in a north-south direction, and
are known in literature as Lumbardy Basin, Trentino Platfomr, Belluno Basin and Friuli Platform
(Bosellini, 1973).
Croda del Becco. Well stratified limestones (Calcari Grigi group)
The sediments that characterize this great carbonate platform comprise the Calcari Grigi Group,
within which it is possible to identify more units (Mt Zugna Formation, Loppio Oolitic Limestone,
Rotzo Formation and Massone Oolitic Limestone).
In the Dolomite area the Calcari Grigi Group comprises a strong succession of dark gray to light
gray or hazel micritic limestones with abundant fenestrae, oolith pockets, mollusks and echinoderms
bioclasts, and rare benthic foraminifers. The layers, sometimes amalgamated, present parallel joints
sometimes slightly wavy, and have a thickness of 30-50 centimeters. Intercalated to these are sometimes
strata of 15-25 centimeters of marly carbonate laminites, whitish in color, that flake in millimeter
sheets and which can give origin to teepee structures. Fragments of these laminites can be found
at the base of the strata within the intraformational small breccias. There are also intercalations of
centimetric horizons of gray-greenish pelites.
Towards the top the succession is less monotonous due to the greater alternation of lithotypes. The
strata, 20-40 centimeters, present flat and parallel joints and sometimes are amalgamated in blocks
of metric thickness. These are micritic, bioclastic and pellettiferous-oolithic limestones, with a color
ranging from gray to hazel and even white. In thin sections one can recognize: dark gray mudstones,
containing rare grains among which small peloids, sponge spicules and indeterminable agglutinate
foraminifers can be identified. There are also dissolution cavities full of spathic calcite and geopetal
cavities. The micritic matrix is locally recrystallized. Also present are fossiliferous and pellettiferous