Geomorphological description

The Sciliar/Schlern – Catinaccio/Rosengarten – Latemar system, has rather accentuated morphological unity, although it presents a great variety of landforms, with sheer dolomite peaks up to nearly 3000 m and high relief energy. At its feet there are mild slopes of clayey-arenaceous or volcanic rock types, in places covered by vast talus cones and scree slopes. From a morphotectodynamic viewpoint, no particular morphostructures are found, apart from an alignment of landforms linked to a neotectonic fault located in Val di Fassa, north of Pera. This is a right-strike slip, with alignments of saddles, escarpments, landslides and erosion forms. This structure is also responsible for the piracy of the upper Val di Dona by the Torrent Udai. Furthermore, tectonic movement is also shown by the displacement of a series of intrusive dykes. From a morphoselective viewpoint, the first cause of landform variety can be found in an area’s structure and, in particular, in its lithology and in the tectonic configuration of its rocks. From a morphotectostatic viewpoint, the escarpments in the dolomite group show a rough correspondence between the directions of tectonic disturbances (faults and fractures) and the margins of slopes. More in particular, some sub-parallel tectonic lines which intersect the Sciliar Natural Park, between Fiè (to the W) and Catinaccio d’Antermoia (to the east), constrain the meridian trend of some valleys, as the Duron and Ciamin valleys, and alignments of peaks, as the crests of Cime di Terrarossa/Roterd Spitz and those between Cima di Mezzodì and Cima Principe. Also the structural surfaces that can be observed in Col di Udai are characteristic of this area. Spectacular landforms can be seen, such as Torri del Vaiolet and the southern slope of Catinaccio/Rosengarten, isolated by a series of joints in the Sciliar Dolomite formation. Crests of Denti di Terrarossa/ in correspondence of a bundle of tectonic fracturesCrests of Denti di Terrarossa/ in correspondence of a bundle of tectonic fracturesFrom a morpholithological viewpoint, the system shows various rock types, which have created very diverse landscapes, both at a small and large scale. The main mountain massifs, such as Sciliar/Schlern, Catinaccio d’Antermoia and Latemar, are bordered by steep escarpments in Sciliar Principale. In sharp contrast with them are the mild slopes at their foot, which have been prevalently modelled in the arenaceous-marly rocks of the Permian (Val Gardena and Bellerophon Formations) and, in particular, the Lower Triassic (Werfen Formation). Also some Dolomite passes have been shaped in the particularly erodible formations of the Permian and Lower Triassic, such as the Costalunga Pass, which separates the mountain group of Catinaccio/Rosengarten from Latemar, or the Lavazè Pass, west of Pala di Santa, or the Nigra Pass, west of Catinaccio/Rosengarten. Dolomite morphological features are in sharp contrast with those in porphyry: for example, Latemar compared with Pala di Santa. The latter consists of a mildly inclined plateau whereas the former is a rock massif with steep walls. There are many ledges in correspondence of the Buchenstein Formation, on the faces of Catinaccio/ Rosengarten and Latemar, and Travenanzes Formation on Sciliar/Schlern. There are also numerous gorges and canyons separated by high rock towers, set in a typical Dolomite landscape. From a morphoclimatic viewpoint, the landscape shows considerable evidence of LGM and Lateglacial glacialism. Earlier debris deposits were found near Moena and Vigo di Fassa, just to the east of this system. These are alluvial and slope deposits, stratified and generally cemented with particle sizes ranging from blocks (sometimes rounded) to sand. Their thickness ranges from a few metres to 20-30 m. They are in turn covered by LGM moraine deposits and should therefore be ascribed to an interglacial period (probably Riss–Würm). Some exhumed landforms, in the permian porphyries along the Duron valley, could be ascribed to a interglacial or pre-glacial period. During the LGM the plateaux were covered by ice caps, from which only the highest peaks emerged. The valleys were filled by long tongues of slowly moving ice. It is presumed that the glacier which flowed over Alpe di Siusi/Seiser Alm came from Val di Fassa and passed through Passo Sella, whence it flowed into the glacier of Val Gardena. The oldest materials can be attributed to a Pleniglacial or early Lateglacial glaciation and are found as thin deposits spread along isolated areas of the right-hand side of the Val di Fassa. The moraine deposits in the form of terraces and frontal systems, visible almost everywhere along the axis of the valley and on the sides of the Valle del Vaiolet, may be ascribed to the LGM.Catinaccia d’Antemoia from Sciliar / SchlernCatinaccia d’Antemoia from Sciliar / Schlern The moraine deposits observed in Monzon, north of Pera, and in the hamlet of Pian, NE of Campitello, are an isolated example of advancement during a phase of general retreat. The principal forms that can be attributed to the erosional action of glaciers are the cirques located on the highest points of Catinaccio d’Antemoia (which are currently subject to deterioration). The ridge line that connects Torri del Vaiolet to Pale Rabbiose is marked by a continuous sequence of glacial cirques. Some are well preserved, such as Coronelle and Cigolate, others, such as those at Rabbiose Pale, have been partially destroyed. Other forms of erosion include roches moutonnées, rock bars and small basins that, together with karst processes, created two lacustrine hollows currently located in Val d’Antemoia, just to the south of Val di Lusia. Other fairly well preserved Lateglacial traces are found on Latemar, uphill of Malga Gardonè and south of Doss Cappello. An example of transfluence of the LGM glacier can be observed in proximity of Passo delle Pale, where it is oriented towards the Lavazè valley. Glacial modelling created numerous small lakes. However, over the course of several millennia, they have been transformed into peat bogs and wet meadows by gradual burial. During glaciation the highest tops emerging from the ice were modelled by periglacial processes which continued after the glaciers’ retreat and still shape most of the system’s landscape to date. As a consequence, the top parts of the slopes were bordered by glacionival degradation escarpments. In correspondence with tracks there are talus cones and scree slopes. Other periglacial phenomena observed in the area of the system are gelifluction processes and protalus ramparts. With regard to slope movements, several earth flows and two landslides connected with glaciopressure phenomena are found. The former, approximately 2 km upstream of Campitello di Fassa, obstructed the Duron Valley. This landslide body is made up of Ladinian volcanic rock which collapsed from the northern slopes of Mount Ponsin in two successive periods. The occlusion of the valley narrows and the consequent formation of a lacustrine basin can be attributed to the first slide, by far the more important. During the maximum expansion of the LGM, the glacier of the Duron Valley, originating in the eastern part of the Sciliar/Schlern ridge, and a branch of the Gardena Valley glacier flowing into the Fassa Valley to the west of Sasso Piatto, converged directly upstream of this landslide. The latter slope movement, which originated from the SE slope of Punta Scalpello, between Mazzin and Pera di Fassa, is located at the confluence of Val di Fassa and Val Soial which contained a glacial branch stemming from Catinaccio/Rosengarten. Other movements are found in the Sciliar/Schlern plateau. The entire Mt. Pez area is affected by a deep gravitational movement consisting of highly developed lateral-spreading. Typically, these complex processes developed where a brittle rock mass – intersected by vertical fractures and not confined laterally – rests on ductile rock types. In this particular case, the N-S and E-W joints splitting up the Dolomia Principale into a number of blocks with different behaviour, have allowed rain water to rapidly seep into the underlying argillites of the Travenanzes Formation. As these formations swell, they penetrate the overlying dolostones from below through the discontinuities, favouring fracture widening. In this way, the large blocks of Dolomia Principale push each other away (lateral spreading). There are also some rock falls and debris flows, such as those of Lavina Bianca, in the area of S. Cipriano. This system shows marked regional extrinsic and intrinsic geodiversity, compared with other non-dolomite areas: its characteristics of high relief energy, with representative examples of structural landforms, widespread glacial evidence and traces of mass movements with glaciopressure implications, make it a model of geomorphological evolution in a dolomite area.