In this area the stratigraphy outcropping, covers a very long interval of time: here the most complete stratigraphic series of the whole Dolomites are present, starting from the Cambrian metamorphic basement and reaching the youngest Oligo- Miocene terms. The stratigraphic and sedimentological features of the various formations are well perceptible, even though these are often disturbed by regional tectonic lines that sometimes double the stratigraphic succession. In this system, the depositional environments and the lithologies of the entire Dolomite sequence are well represented, regarding both the terrigenous or terrigenous- carbonate facies, and the carbonate facies, with some stratigraphic peculiarities in the eastern area. This vast sector presents a tectonic setup in the form of a wide syncline with a WNW-ESE direction, having as nucleus Cretaceous sediments. The syncline has been divided into blocks by overthrusts and fault lines, oriented in the most diverse directions. A structural element typical in the Sesto Dolomites are the graben structures with throws of hundreds of metres; structures of particular interest are the so-called "peak overthrusts (sovrascorrimenti di vetta)" within the Jurassic limestones (Remeda Rossa/Rote Wand - Piccola Croda Rossa/Kleine Gaisl, Tofana III and Tofana II, Vallon Bianco, Col Bechei). To simplify the description, this system (the largest of the candidature) may be split into three branches from north to south according to the distribution of the major mountain groups.
Dolomiti di Sesto/Sextner Dolomiten - Dolomiti di Braies/Pragser Dolomiten - Cadini di Misurina
The mountain landscape is characterized above all by sedimentary rocks witnessing the period of time between the Lower Permian and the Upper Triassic: the gently sloping sides to the left of the Sesto valley/Sextental and of the Pusteria valley/ Pustertal consist of up to 2000 m of Val Gardena Sandstone, of the Bellerophon Formation and of the Werfen Formation. To the terrains of the Lower Triassic follows a powerful succession of carbonate platforms and their basins, starting from the Lower Serla Dolomite to the Contrin Formation, which are relatively tabular in their geometry. On this relatively homogeneous substrate lay the jagged crags of the Sciliar/Schlern Dolomite (Gruppo di Rocca e Croda dei Baranci/Haunold- Birkenkofel-Gruppe, Gruppo dei Tre Scarperi/Dreischuster-Massiv, Col Vallaccia) and the Cassian Dolomite (Picco di Vallandro/Dürrenstain, Cadini di Misurina). The more diffuse lithological formations are the Sciliar Dolomite and the Cassian Dolomite forming among others, the Croda Rossa di Sesto/Sextner Rotwand, Cima Undici/Elfer, Monte Popera/Hochbrunnerschneid, Cima Una/Einser, Punta dei Tre Scarperi/Dreischusterspitze, Rocca dei Baranci/Haunold and the Croda dei Baranci/Birkenkofel. These grey rock masses are covered by vary coloured marls and clays layers and by light coloured dolomites (Travenanzes Fm) that condition suggestive changes in our perception of forms, colours and landscapes. In the southern part of the Dolomiti di Sesto/Sextner Dolomiten and of the Dolomiti di Braies/Pragser Dolomiten, the Sciliar Dolomite and the Cassian Dolomite instead constitute, the majestic bases of those real and true monuments of the mountain chain: Cima Undici/Elfer, Monte Popera/Hochbrunnerschneid, Cima Dodici/Zwölferkofel, Monte Paterno/Paternkofel and the Tre Cime di Lavaredo/ Drei Zinnen, whose all peaks are composed of Dolomia Principale. The high plateaux from which the Tre Cime/Drei Zinnen rise with elegance are formed by the Travenanzes Formation (Raibl Fm. Auct) which lies over the Heiligkreuz Formation. The Travenanzes Fm. reaches here notable thickness and crops out with continuity near the saddles: in the mountain morphology it can be identified in the form of benches. In the hollows, it forms an impermeable substrate on which are spread green alpine grasslands and scintillating lakes. This formation hence forms extended flat areas among the massive grey dolomites, such as for example the Alpe dei Piani/Bödenalpe, or it's related to incisions, as at the Forcella Giralba/Giralbajoch, Forcella Pian di Cengia/Büllelejoch, Forcella Lavaredo/Paternsattel or the Forcella S. Candido/Innichriedl. The youngest stratigraphic unit is here the Dolomia Principale, typically characterized by the regular horizontal stratification, which constitutes among others, the famous peaks of the Tre Cime di Lavaredo/Drei Zinnen, the Monte Paterno/Paternkofel and the Croda dei Toni/Zwölferkofel.
Dolomiti di Sennes/Sennes Dolomiten - Fanes - Lagazuoi - SettSass - Tofane - Cristallo
In this sector of the system, the deposition of the Travenanzes Formation (Raibl Fm. Auct), is followed by a very well documented impressive succession of many hundreds of meters of shallow water carbonate sediments. These are represented by the Dolomia Principale, the Calcari di Dachstein and the Calcari Grigi which are characterized by a regular stratification and they form potent sequences that can be found over a large surface area that extends from the nucleus of this zone, as at the Croda Rossa/Hohe Gaisl, to the external parts, such as at the Tofane or at the nearby M. Cristallo. To the north the Calcari Grigi are stratigraphically followed by the Encrinite of Fanes Piccola/Klein Fanes/Pices Fanes and by the Rosso Ammonitico. Even though distributed in limited outcrops and often dismembered by tectonic events, the carbonate-terrigenous rock units that stratigraphically cover the Rosso Ammonitico, allow the documentation of a large part of the Cretaceous. At last, in net stratigraphic unconformity, we find the M. Parei Conglomerate (Oligocene). In the southern portion (Lagazuoi, SettSass, lower edifices of Tofane and of Cristallo), prevalently the Cassian platforms prograding on the corresponding basins emerge; over these follow the vary coloured argillites of the Travenanzes Formation and the Dolomia Principale. The Sett Sass group is one of the symbolic zones from a geological point of view, for the dolomitic stratigraphy, both for the perfect preservation of the depositional geometries of the Carnian carbonate platforms, and for the fossil bearing locations that are famous since the second half of the XIX century. The period of time that is documented there, goes from Late Ladinian (Middle Triassic) to the Early Norian (Late Triassic).
The oldest formations outcrop in marginal areas and are represented by the terrigenous- carbonate basin units of the Upper Ladinian (from the Zoppè Sandstones to the S. Cassiano Formation) and their heteropic carbonate reef formations, that, in a generalized shallowing stand of the basin, lead to the almost complete filling of the Ladinian Carnian basins. The final flattening occurs with the Heiligkreuz Formation that in these areas is very characteristic. On it, lays the Travenanzes Formation followed by the 1300 m thick Norian-Liassic calcareous-dolomitic complex (Dolomia Principale, Dachstein limestones, Calcari Grigi) typical of the Eastern Dolomites.
Stratigraphic and paleontological emergencies
- As can be seen from this impressive list of mappable lithostratigraphic units, this area documents a potent and complete succession of facies and paleoenvironments witnessing in great detail a long interval of the Permian/Mesozoic time, in a thickness of more than 3000 meters.
- The Anisian, Ladinian and Carnian platforms are preserved in three dimensions in all their parts, showing both spectacular examples of heteropy with the basins, and documenting inner platform and lagoon facies.
- In this area the recovery of the bio-constructors after the P/T crisis is documented in one of the most potent and diversified successions of carbonate platforms in the Dolomites
- The finds of fossil plants in this area are very important. In particular the Pra della Vacca/Kühwiesen Lagerstatten (Anisian) had supplied an impressive quantity of plants, fish and even a reptile. Equally significant are the finds of plants in the Ladinian sediments studied since two century ago (Wissmann & Münster, 1841).
- The basin successions from the Anisian, in particular those of the area of Braies/ Prags, are rich in fossil bearing localities studied for years and famous for the invertebrate marine fauna (ammonoids, bivalves, brachiopods) and constructor metazoans.
- In the area of Lagazuoi - Col dei Bos
- Tofane, a section of approximate length of ten kilometers is preserved; there we can analyze in detail the variation in the types of deposition of the Carnian carbonate platforms during all the phases of the crisis of the carbonate producers which occurred at the Julian/Tuvalian boundary.
- The Sett Sass group includes the type-area (Sett Sass group) of Cordevolian (Carnian historic subdivision) introduced by Mojsisovics et alii in 1895.
- At the southwestern margin of the core zone, in the section of Prati di Stuores/ Stuores Wiesen a GSSP (Global Boundary Stratotype Sections and Points) has been proposed for the base of the Carnian (228 My). The formal proposal has been done at the end of the 90s (Broglio Loriga et al., 1998; 1999) and now it has been ratified and it will be approved during the next International Geological Congress hold in Oslo in August 2008.
- In the ridge between the Sief and the Sett Sass slopes and, above all, between the Piccolo Settsass and the area of Prati di Stuores/Stuores Wiesen, there are various locations that are important at world level for palaeontology, palaeoecology and biostratigraphy, for the abundant foraminifera micro-fauna, Ostracoda, Roveacrinida, Holothurioidea, Asteroidea, Ophiuroidea and for the macro-fauna of bivalves, gastropods, brachiopods, ammonoids, serpulas, remains of coral and sponges.
- The reef of the Piccolo Settsass (Richthofen Reef ) and the spectacular progradational one of the Sett sass represent one of the first known examples of fossil reefs and today they still are a seismic scale example of the depositional geometry of terrigenous-carbonate systems.
- For the Carnian interval, we remember the Heiligkreuz Fm, which is very rich in fossil fauna and where, beside the many invertebrates, have been found remains of the cranium of a Stegocephalus (amphibian) and dinosaur footprints, which are among the oldest in the world. - In the area of the Tofane, within the Carnian sediments of the Heiligkreuz Formation amber among the oldest known have been found. This amber contains one of the oldest association of preserved soft-bodied microorganisms such as bacteria, fungi, algae and protozoans.
- From a stratigraphical point of view, we mention the presence of a conglomerate near Monte Parei, that, unique in the Dolomites, is attributed to the Tertiary. The formation crops out below the peak of the mountain on a morpho-structural ledge directed E-W at an altitude of approximately 2580 m; a further outcrop is present at height 2377m between the Col Bechei di Sotto and Croda d'Antruilles. The fossils association (foraminifers type amphystegina) found in the sandstone strata, allows this formation to be referred to the Oligocene-Miocene boundary, approximately 25 million years ago.