DOLOMITES - Annexes 2-8 - Provincia di Udine

NOMINATION OF THE DOLOMITES FOR INSCRIPTION ON THE WORLD NATURAL HERITAGE LIST UNESCO
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Sedimentation continued bed after bed in the basins that separated these reefs, originating from the
erosion of vulcanites and from the precipitation of carbonates exported from the platforms (S. Cassiano
Formation). This formation, world famous for its fossiliferous content, was originally named
Cassianer Schichten by Münster (1834), from which the name San Cassiano Beds derives, used in
Italian geologic literature and geologic cartography. The San Cassiano Formation is very well represented
within core and buffer areas; some areas, such as Prati di Stuores, the area of Sett Sass, the surroundings
of Cortina d’Ampezzo, the area of Picco di Vallandro/Dürrenstein, the Forcella Giau (to
quote just a few), are famous for the noteworthy fauna fossils, known by the scientific community
thanks to numerous paleontologic writings produced from the second half of the 1900s mainly by
German speaking researchers, as well as the patient work of R. Zardini in more recent times.
Panoramic view of Giau Pass. Notice the contrast between the green fields grown on basinal and fine sediments (WEN-SCS) and
the high and rocky cliffs of La Gusella (Cassian Dolomite).
The San Cassiano Formation comprises a complex of alternating pelites, marls, pure to marly micrites,
oolithic calcarenites, bioclastic and oncolithic calcarenites and calcirudites. Carbonate lithotypes
are mixed in various proportions with sandstones of volcano-detritic origin and produced by
the erosion of the crystalline basement, probably exposed in the emerged areas situated to the south
of the current Valsugana Line. Hybrid arenites are extremely frequent, with a mixed carbonate-terrigenous
composition, which would imply a mixing of the two components in shallow water before
resedimentation in the basin. The dominant are light gray and yellowish in color. The arenite strata
present thicknesses between centimeters and decimeters, while the fine parts are present both in
sets from dozens of centimeters to meters and as thin interbedding between the arenite layers. The
depositional structures exhibited by the arenites (erosional base, direct gradation, plane-parallel lamination,
current ripples, flute-casts, absence of evident wave structures) are indicative of turbiditic
transport with episodes of debris-flow and slumping. The San Cassiano Formation is, at least in the
mid to upper parts, dominated by the carbonate component originating from the prograding platforms,
even when the siliciclastic import does not decrease. Near the platform areas, the Formation
is clearly organized in cycles of coarsening-up/thickening-up (CU/TU) facies of various thicknesses
from a few meters to a little over 10 meters (Masetti et alii, 1991), that is lost in the more central basin
areas. The more proximal CU/TU cycles end with carbonate olistolith swarms deriving from the
external margin of the platforms (‘Cipit Limestone’ Auct.). In the eastern sector (far from the contemporary
carbonate platforms) and in the southern sector (closer to the siliciclastic coastline), the
terrigenous fraction can dominate the carbonatic one. The S. Cassiano Formation is indicated to be
Upper Longobardian, and to most lower Carnian Stages (Julian according to Krystyn, 1978) on the