Geotrail Wolayersee

The Wolayer Valley in the East separates two entirely different realms of rocks. The bright limestones of the Kellerwand in the south were formed some 400 million years ago in a shallow sea. In contrast, the colorful sandstones, shales and limestones of the Rauchkofelböden in the north were deposited between 460 and 330 million years ago in deeper seas. The present-day distance between these two rock types is too narrow to be explained by natural variation in the original depositional environments. Their present vicinity is due to almost unimaginable movements of huge rock masses that brought the separate rock realms together. This displacement of rocks leads to a structure which geologists call a fault. Because of the close neighbourhood of sediments of shallow and deep seas the Lake Wolayersee region got world renowned.

Stopping Point 2 - The Lambertenghi Ridge

Looking north, you can see the Lambertenghi Ridge, the ridge west of the Volaia pass that connects to the north-east corner of Mount Capolago. It represents, in some ways, a synthesis of the geological makeup of the Volaia area. A thrust fault connects two different sedimentary sequences: one is made up by rocks that deposited in an open sea over a time frame going from the Upper Ordovician to the Lower Carboniferous. Another sequence is of equal age but constituted, especially in its Devonian part, by rocks deposited in lower sea environments.

Stopping Point 3 - A boundary between two periods: the RLF III section

The RFL III section is an outcrop of about twenty meters highlighted by a trench dug during the First World War. It is located in the basin south of the Refuge Lambertenghi-Romanin, about a hundred meters further downstream, near the path that leads to Mount Capolago. The grey limestones that emerge along the western rampart of the trenches seem equal to each other, but in reality, they contain the limit between two geological periods: the Silurian and the Devonian. This limit was recognised thanks to numerous micro-palaeontological and stratigraphic investigations.

Stopping Point 4 - A complex structure

The Wolayer Pass is the saddle that separates the imposing limestone cliffs of Mount Capolago/Seekopf to the west from those of Cima Lastrons del Lago/Seewarte und Coglians/Hohe Warte to the east. It owes its origins to an important tectonic line north-south, a fault that cuts the cliff deposits, remains of the oldest marine environments. A fault is a fracture within a rocky body, which testifies to the movements of the block in which the body was divided. This fault is characterised by a rather important vertical movement, but also by a relative horizontal displacement which is estimated in about half a kilometre (546 yards).

Stopping Point 5 - The age of reefs

During the Devonian Period, a shallow warm ocean with coral-type reefs extended across the future Carnic Alps. The center of the reef was located in the region of present day Lake Wolayersee. The deposits of the lagoon form the Biegengebirge mountains as we see them today. The Hohe Warte and Seewarte represent a reef core composed of corals, sea-lilies, snails (gastropods), shells (bivalves), stromatoporoids (sponges) and Orthoceras (tubes-form cephalopods). The large block at this stop contains excellent examples of gastropods. Nearby, in the surrounding debris from mountain Seewarte, numerous other fossil examples can be found.

Stopping Point 6 - Lake Wolayersee - in the centre of marine deposits

The Lake Wolayersee developed during and after the last Ice Age, the so-called Würm glacial period, which started around 115,000 years ago. Back then, the glacier in the area carved out a trough and flowed over the Wolayer Pass in the south towards northern Italy. Once the ice had retreated, around 10,000 years ago, the trough filled with water and formed the lake which in places reaches 14 meters depth. The lake is fed by the influx of underground water from the surrounding talus material. The maximum water temperature is 14 °C.

Stopping Point 7 - Appreciating the little things

At this stop you can see spiral-like fossils within the limestone cliffs which are up to 5 centimeters long. These are 370 million years old goniatites, the extinct predecessors of ammonites of the Devonian Period. Much more significant for geologists are the jawbone remains of conodonts (not visible to the unaided eye). The jawbone forms of these extinct marine organisms changed quickly over time; hence they are ideal for determining the exact relative age of rocks. Despite their geological importance, the appearance of these animals remained unclear for over 100 years until 1983 when the first complete fossil was found. Since then we know that they were approx. 5 centimeters long and resembled eels.

Stopping Point 8 - Lifeless deep-sea rocks

This site is the home of the youngest rocks along the Geotrail with an age of approx. 330 million years. The brownish Hochwipfel Formation was formed in the course of the incipient, globally-ubiquitous mountain-building process called the Variscan Orogeny. Sea basins subsided and huge quantities of loose material in the form of turbidity currents were transported into the deep oceans. This deep-sea environment was unfavorable for fossilization, therefore fossils are rare in the shales, sandstones and breccias of the Hochwipfel Formation. The Hochwipfel Formation is the dominating rock type in the Austrian part of the Carnic Alps east of the Plöcken Pass, whereas west of Lake Wolayersee it is only exposed locally.

Stopping Point 9 - „Animal” flowers and other controversial creatures

This fossil-rich limestone block is derived from the Kellerwand cliff in the south and is dominated by sea lilies (crinoids). Despite their flower-like appearance, they do not belong to flora but are faunal remains. A stem with roots anchors crinoids securely to the sea bottom; the top end contains the so-called crown from which the arms of the animal extend. Usually only fossil parts are preserved, here especially cross sections of the crown or stem segments. Fossilized corals and extinct stromatoporoids (sponges) are also common in this block. The latter are thought to have been a type of sponge (although this is still a subject of debate) and were important in forming reefs.

Stopping Point 10 - The superlative rock face

The impressive Kellerwand cliff and the Hohe Warte mountain (2,780 m) in the south represent the highest peaks in the Carnic Alps. Aloft the Kellerwand hides the southernmost glacier in Austria, the Eiskar. The Kellerwand rocks were formed in the Devonian Period over some 30 million years. The lower parts of the Kellerwand are distinctly bedded. They are deposits of an open sea with depths of several tens of meters and more, while the overlying massive parts represent a former reef core and the fore-reef. The conspicuously folded layers in the center part of the cliff were caused by tectonic processes. The red Findenig Limestone of the Rauchkofel in the north was also deposited far away from the reef in the open sea.

Stopping Point 11 - Mountains on the move

Looking behind, we may get an idea of the tremendous natural forces having a large effect on earth´s surface. The pale Wolayer Limestone in the east has no continuation across the gully in front of us where the reddish Findenig Limestone is exposed. The rock association got out of order because of tectonic processes which have detached and shifted entire rock formations, called a fault by geologists. Through this movement the rock was broken and fractured, making it vulnerable to erosional processes. Because of these processes, faults are usually the origin for trenches and entire valleys. The Gailtal-valley itself is part of the longest tectonic fault of the Alps, namely the 700 kilometers long Periadriatic Lineament.

Stopping Point 12 - Evidence of deeper seas

The reddish-brown calcareous rock is named Kok Formation. The rock was deposited in moderately deep shelf seas that covered the area 430 million years ago. Characteristics of the Kok Formation are dark iron-manganese-crusts and a high number of representatives of Orthoceras (“straight horn“), predecessors of the ammonites. At the same altitude, 25 meters further to the southwest we encounter an entirely different rock. The black Bischofalm Slates comprise mainly quartz minerals and were deposited in a calm ocean basin. The quartz derived from radiolarians, tiny single-celled organisms. Due to very weak ocean currents, the water became depleted in oxygen. Therefore, organic material was not decomposed by aerobic processes and accumulated in the rocks in the form of black carbon.

Stopping Point 13 - The oldest of the rocks

At this site we encounter the oldest rocks of the entire Geotrail: The Himmelberg-Formation and the Wolayer Formation. Both were deposited around 450 million years ago in the Ordovician Period. The surrounding area of this stop is composed of the grey-green Himmelberg-Sandstones which are river transported sediments that have been deposited near a shoreline. They are usually fossil-free and comprise mainly quartz. Further to the south, a grey ridge of rock catches the eye. This is the slightly younger calcareous Wolayer Formation, which is a usually fossil rich marine sediment. There is an easy way to distinguish both rocks here in the field: The striking yellow-green map lichen grows solely on lime-free surfaces, so it is found only on the quartz-rich sandstones.

Stopping Point 14 - Nodular limestones - A peculiar structure

The nodular limestones of the Findenig Formation developed from a clay-rich lime mud which was deposited at sea depths of 100 meters or more during the Devonian Period, some 390 million years ago. It mainly comprises microscopically small shells and skeletons of marine organism (plankton). Dark and light red layers alternate within the rock. The dark layers are rich in clay while limestone dominates the light red sections. The eye-catching net-like structure developed through compression of lime mud, which caused the separation of clay and lime particles. The color is derived from finely dispersed haematite, a ferrous mineral.

Geosite 1 - A mass grave of primeval squids

This approximately 420-million-year-old limestone boulder from mountain Rauchkofel shows remarkable numbers of representatives of Orthoceras (“straight horns“). They are filled with white calcite. Locally, these marine animals were up to 9 meters long. They were the predecessors of the famous ammonites. The bright circles with diameters of up to 10 centimeters are the fossilized cross sections of the central bladders (buoyants) of the free-floating sea lily Scyphocrinites.

Geosite 2 - Fragmentary history of the Earth

At this site we see a communication trench from Word War I. Here the light-grey, 450-million-years-old Wolayer Formation is bounded by the reddish-brown, 430-million-years-old Kok Formation. This gap of approx. 20 million years geologists explain by the rising of the sea floor or the retreating of the sea, where no sedimentation took place. The limestone of the Kok Formation contains large numbers of representatives of Orthoceras. The calcareous Wolayer Formation is rich in fossilized small ringlike stem and tentacle segments of cystoids, which belong to the echinoderms. They had a characteristic sack-like body covered by numerous calcareous plates.