The stratigraphy outcropping in this area covers a very long interval of time: here there is one of the most complete stratigraphic series of the whole Dolomites, starting from the Early Paleozoic metamorphic basement and reaching the Cretaceous terms. The stratigraphic and sedimentological features of the various formations are well perceptible, even though these are often disturbed by regional tectonic lines like the Valsugana Line: this complex tectonic structure is the most important of the Dolomite Region and it split the System (the second for areal extension of the candidature) into two branches.
Dolomiti Bellunesi – Vette Feltrine - Brendol-Piani-Eterni-Cimonega - Schiara-Talvena - Pramper-Cime di San Sebastiano
The succession in this southern sector is very thick and goes from the Sciliar Dolomite to the Scaglia Rossa. The Vette Feltrine certainly represents the most remarkable area of the system from a stratigraphic and paleontological point of view. This is due to the great variety and quantity of fossils that have been studied ever since the 19th century and to the classic formations that here show very peculiar facies and relevant variations in thickness. For instance, the Calcari Grigi in the Vette are known worldwide because they contain fossils of calcareous and siliceous sponges that belong to a geological era in which this kind of remains are very rare; moreover they contain a layer of glauconitic encrinites very rich in ammonites (Hildoceras, Harpoceras,...) that are perfectly preserved and boast an extraordinary stratigraphic value (Coston delle Vette, Col Fontana). Given its wide and varying paleontological content, the Rosso Ammonitico Inferiore is no doubt the most interesting formation. This unit is followed by several other formations: the Fonzaso Formation, the Rosso Ammonitico Superiore and the Biancone (Vette della Vallazza and Pavione Mount).The Cimonega area stands out in the rock system for its typical Dolomitic appearance. It consists of a block of dolomite that detached from the wide Ladinian platform of the Pale di S. Martino and overthrusted south of the Valsugana Line overlying the Cretaceous and Jurassic grounds of the Neva Syncline. The most eastern area is represented by the highland of Piani Eterni-Erera where outcrops a complete stratigraphic succession typical of the Trento platform. The Middle Jurassic succession (Calcari Grigi Group - Rosso Ammonitico Sup.) is here particularly condensed due to the frequency of stratigraphic hiatus and its units are also characterized by rapid lateral variations. The eastward decreasing in thickness of the Fonzaso Fm and the related increasing of the Vajont Fm are important evidences that during the Middle Jurassic, the Piani Eterni-Erera used to be a structural high at the margin of the Trento platform, surrounded by deeper waters. In the deep canyons and on the inaccessible walls of the eastern Schiara–Talvena group it’s possible to observe the outlines that led to the fragmentation of the Triassic platform and that affected the stratigraphic successions of the Belluno basin, the tectonic configuration of the group and, indirectly, the evolution of the landscape. Some of the formations described above (Dolomia Principale, Calcari Grigi) have been here replaced by the relative formations of basin facies (Soverzene Fm, Igne-Calcarenite Fm in the Val degli Erbandoli), while others feature much higher thicknesses (Calcare del Va-jont, Fornazo Fm); for instance, the group of the Calcari Grigi shows a thinner thickness to the east of the Medone Line until it disappears completely to the east of the Marmol paleo-line. This unit is replaced by thin, grey bituminous layered dolomites that alternate with thick breccia bodies, coming from the Trento platform (Schiara Dolomite), and from the grey bituminous dolomites with beds and nodules of black chert (Soverzene Fm). The geologic scenario changes quikly northward: the Cime di San Sebastiano and the Pramper are mainly characterized by the Dolomia Principale that lies on the conglomeratic and terrigenous-carbonate facies of the Travenanzes Formation.
Pale di San Martino-San Lucano – Civetta-Moiazza
The stratigraphic series cover a period from the Early Paleozoic to the Late Carnian- Norian. The formations in this branch mainly witness the geological history of the Permo-Triassic and, in particular, the Anisian-Ladinian periods are very well documented. The oldest lithologies that can be found, the schistose crystalline basement of the Early Paleozoic, outcrop to the south of the Pale Group, in the Primiero hollow. The Complesso Vulcanico Atesino narrows off to the south and east, and it is only evident in the north-western part of this group. The impressive complex of the Pale of S. Martino and the lower edifice of the Civetta-Moiazza group is formed by a large platform body developed between the Anisian and Carnian periods. It extended in a NE-SW direction, moving SSE, N-NW, as highlighted by the depositional geometries and lateral relationships with the coeval basin deposits. The basement of this important paleogeographic domain is made of Dolomia dello Sciliar/Schlern that here reaches a thickness of 1500-1800 m. In the west-northwestern part we find volcanoclastic rocks, lavas and dykes that also have a consistent and thick lateral continuity, ranging from just a few through to tens of meters. They sutured in onlap the old slope of the Sciliar platforms, perfectly preserved on the western side of the Pale di S. Lucano. At the Monte Agner and Mt. Pelsa, the upper part documents the carbonate platform sedimentation after the volcanic paroxysmal phase (Cassiana Dolomite). The superimposition of the Cassian platforms is marked by a spectacular paraconformity: those are set on a previously eroded substrate after a period of emersion, characterized by paleo-karstic features. The higher edifice of the Civetta-Moiazza group is characterized by a 1000 m. thick regular sequence of dolomites and limestones dating from the Norian and Liassic (Dolomia Principale, Dachstain limestone, Calcari Grigi). These sequences lay or directly on the Cassian Dolomite, or by the interposition of the Heiligkreuz Fm and of the Travenanzes Formation.
Stratigraphic and palaeontological emergencies
– This system shows in great detail a considerable succession, that goes from the Early Paleozoic throughout the entire Cretaceous.
– The southern sector documents the entire structural and stratigraphic evolution of the south-alpine passive margin, particularly in the area of the Schiara Talvena, part of the margin itself is preserved and fossilized under the post-rift deposits of the Late Jurassic.
– Extraordinary exposures of the drowning facies of the Jurassic Trento platform.
– The pre-volcanic platform (northern sector) is three dimensionally preserved in all its parts, and shows spectacular examples of geometric relationships with the volcanic bodies that onlap its slopes.
– The top of the pre-volcanic reef documents an important emersion phase, with widespread paleo-karstic features of the Triassic, with dolines and caves later filled with breccias and sealed by later generations of carbonates related to low tides.
– The Anisian-Ladinian basin and intra-platform successions are rich of fossil areas, which have been studied for more than 200 years.