Geotrail Findenig - Passo di Lanza
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Geotrail Findenig - Passo di Lanza
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Stop 1: Stromatoporoids at Cason di Lanza
Near the Cason di Lanza, along the forest road that goes up towards the Val Dolce are outcrops of grey limestones from the Middle Devonian. You can pick out numerous fossil remains, the most abundant, which appear as thin tubes, are Stromatoporoids, distant relatives of the current sponges that lived in the lagoons protected within the bodies of the reef. Sections of some corals and the rather rarer brachiopods can also be distinguished. These rocks are called informally “Stromatoporoid limestones” due to the abundance of the remains of these organisms.
Stop 2: Outcrop of Val Gardena Sandstones
The forest road is crossed by a narrow strip of dark red rocks that stand out from the grey and brown ones. They derive from the ancient sands of a desert environment and were formed about 260 million years ago, at the end of the Palaeozoic, during the Upper Permian. They are called the Val Gardena Sandstones and are widespread further west, near the Rio Cordin. Their peculiarity is that here they have been set among older rocks by the tectonic upheavals that generated the Alps.
Stop 3: Panorama across the Val Dolce
From this vantage point, equipped with signs, one can observe one of the most evocative parts of the area called the Val Dolce. The name derives from the characteristic morphology that contrasts with the rugged limestone walls of the Creta d’Aip of the Monte di Val Dolce and the Cavallo di Pontebba which together form the backdrop. These differences are due to the differing degrees of erodibility of the outcropping rocks.
Stop 4: Fossil tracks on the path
Here we find traces left by organisms that lived on the seabed during the Upper Carboniferous. These are “footprints” resulting from the activity of invertebrates that moved, fed and excavated burrows and tunnels in the muddy sediments. It is difficult to understand which animals made them because almost always where fossils tracks occur no shells or other fossilized remains are found. This is due to the environmental conditions, which did not favour the conservation of organic remains, or because the animals that left them had no hard parts to fossilize. These “ichnofossils” are a fundamental testimony for a more complete view of the life of the past.
Stop 5: The Grotta di Attila
The characteristic shape of the entrance to this karst cave, which resembles a lock or the hilt of a sword, has given rise to various legends. The most famous is linked to the passage of the Huns led by Attila through these areas. The treasure of the heathen leader (which has never been found) is alleged to have been hidden here. The cavity, crossed by the stream that collects the waters of the peat bog, consists of a tunnel almost 500 metres long.
Stop 6: Panorama across the peat bog of the Grotta di Attila
Looking south, you can see the peat bog where the Grotta di Attila opens. These peat bogs, quite widespread in the Cason di Lanza area, are marshy pieces of land derived from the natural infilling of ancient ponds shaped by glaciers. Particularly important for their ecological value, these peat bogs contribute to making this part of the Carnic Alps unique.
Stop 7: Algal oncoids on the saddle
The strange structures, observable in these rocks, are called algal oncoids and are the result of the deposition of concentric layers of calcium carbonate around fragments of shells or rock, by cyanobacteria. These structures are still being formed today on seabeds characterized by the influence of waves or strong currents. In the Carnic Alps they are located in the Lower Permian of the Val Dolce Formation (= Austrian Grenzland Fm).
Stop 8: Panoramic view across the Forca di Lanza
Looking south, we can observe the pale rocks of the Devonian cliffs of Monte Zermula and the Zuc della Guardia. The more rounded form of M. Pizzul, in the background, is due to its rocks being more of the open sea coeval with the reef and thus more easily eroded. These two sequences, deposited in relatively distant areas, are now almost in contact with each other as a result of the tectonic movements that led to the formation of the Alps.
Stop 9: Panoramic view of the Cima di Lanza
The stratified aspect of the Cima di Lanza that we can observe to the east is due to an alternation of more compact calcareous banks and less cohesive pelitic strata. These rocks were laid down between the Upper Carboniferous and Lower Permian (about 320-280 million years ago) in a period of frequent variations in the sea level, due in part to massive glaciations.
Stop 10: Overview of the Pale di S. Lorenzo geological fault
On the south-west slope of the Pale di San Lorenzo the deformations undergone by the Permo-Carboniferous rocks during the Alpine Orogenesis are clearly visible. These very evident folded limestone layers are sometimes twisted and sometimes interrupted and / or displaced by sub-vertical faults.
Stop 11: 150 million years in 150 steps
In the next 150 metres you will travel through 150 million years of Earth's history. Look closely at the colours of the rocks! There are some that are a deep red and that settled on gigantic alluvial plains near the coasts about 260 million years ago, when the environment was characterized by desert conditions. There then follow the brownish rocks of the Auernig Formation rich in fossils, dating back to about 300 million years ago.
At the point where the Alta Via Carnica meets the Via delle Malghe, you can observe black rocks dating back to 410 million years ago from deeper marine strata.
Stop 12: The “2-shaped” fold
On the western side of Mount Cordin there is a clearly visible layered structure, dubbed by the locals “The fold in the form of a 2” for its characteristic shape. Its structure and excellent visibility are provided by the red rocks of the Val Gardena Formation, folded to form a number 2 in pale dolomitic rocks. The fold is among the most imposing deformation phenomena of the Carnic Alps.
Stop 13: Petrified eggs?
On this spot you will find a rock formation that is common between Pramollo and the Zollnersee lake bearing round inclusions similar to nuts, with dimensions that can reach those of an egg in rocks with a fine consistency. These are called concretions and are not fossils, but anorganic formations. Substances such as manganous and ferrous oxide are released in the rock and transferred due to the absence of oxygen. When oxygen is again present in sufficient quantity, these substances disappear and solid aggregates are formed, the concretions. Mineral precipitations, for example, are recognizable in the calcareous deposits in kettles.
Stop 14: The fold in the rock
At this point it is possible to observe a fold in the rock, originating from the Alpine Orogenesis. As the sketch shows however, it is affected by the phenomenon of erosion. In rocks there are two types of deformation. In detail, massive rocks such as limestone deform with fracture, are friable and form cracks. Deformation without fracture however is typical of rocks with a fine consistency, such as those visible at this stop and they react in a plastic fashion, forming folds. Here you can see a rock that has a very sharp fold, with a characteristic thickness of the layers.
Stop 15: Sea and land carved in stone
On the rock wall at the edge of the path, you will come across rocks of the Auernig Formation dating back about 300 million years ago and which formed the sea coast at a time when it was very populated with life. These rocks are made up of marine and coastal sediments and here it is possible to observe both. In the lower part there are grey limestones laid down in a warm and not very deep sea. When the sea receded, the rivers brought sand that became consolidated, forming brown sandstones (visible here above the limestone). At the next stops you will discover more details about this rock formation.
Stop 16: Limestone producers
Here you can see the most important limestone producers of the Auernig Formation, the calcareous algae. To perform photosynthesis, these organisms needed sunlight and therefore lived in the sea at depths of between ten and thirty metres. When they died, their calcareous skeleton disintegrated, mostly becoming a lime-based paste. The cases in which a skeleton has remained intact are rarer. Here you can see two of the most common types of calcareous algae: stick-shaped and salad leaf-shaped. Their scientific names are real tongue-twisters: Anthracoporella spectabilis and Archaeolithophyllum missouriense.
Stop 17: Tracks in the rock
The slabs of rock with a polished surface observable at this point also belong to the Auernig Formation. On these rocks dark circles about one centimetre in diameter can be frequently found and are sections of excavation tracks (Skolithos) of invertebrate animals that once populated the sedimentary areas close to the coasts. With a little luck it is possible to identify another type of track (Psammichnites) about a centimetre wide bearing a median line. A snail-shaped mollusc with an organ similar to a proboscis is believed to have produced this track when going in search of food.
Stop 18: “Animal” Flowers
In the limestone rocks at this stop there are sections through crinoids (sea lilies), the commonest fossils of the Auernig Formation after the calcareous algae which were mostly echinoderms growing firmly attached to the bottom and which still populate our seas today. They consist of a root, a stem and a crown with tentacles, which look very like flowers. When they die, sea lilies decompose very quickly and it is precisely for this reason that specimens complete in all their parts represent very rare finds. The thickness of the stems that can be seen here suggests that the sea lilies back then had a height of 50 – 100 centimetres.
Stop 19: Peaks and hollows
Around Lodintörl it is possible to observe the imposing, almost white, limestone relief of the Auernig Formation, or what is presumed to have been a limestone reef. Here, in a marine habitat characterized by optimal conditions, living organisms were able to reproduce in large quantities and contribute to the formation of the reef.
South of the Italian – Austrian international border is an almost circular pit formed by erosion and about 200 metres in diameter. This is a doline or sinkhole, a karst phenomenon with a conical funnel shape. The name derives from the Slovenian word meaning “valley”.