GEO FACTS
The geology of the Bletterbach Canyon
The first scientific evidence in the surroundings of the Bletterbach gorge dates back to 1891, reports about geological funds from the Bletterbach, however, were first compiled some decades later.
Only since the 1930s, Leo Perwanger, an engineer from Redagno-Radein, provided a description of the Weißhorn’s geological structure, of carbonized plant remains and of petrified marine animals found in the gorge.
In 1948 scientist Piero Leonardi run into the first footprints in the gorge and issued a series of scientific publications and papers.
In the 1970s, Leonardi worked extensively in the Bletterbach gorge together with scientists and students of Ferrara, Rome, Padova and Cagliari University. He organized the very first expeditions and started a systemic research work. The Viennese scientist Wilhelm Klaus documented fossil pollen for the first time in the early 1960s.
Since 1973, researchers of Utrecht University have been working on plants fossils. For all these years, Josef Perwanger supported the research work, and gave his name to two footprints of the Bletterbach gorge he had discovered himself.
The fact that many fossils are found in a confined space, the gorge’s good accessibility and clear recognition of different petrified stratification make this UNESCO World Heritage site to a classic example for science.
To date, scientists are engaged in analyses of the Bletterbach gorge’s geology – in close collaboration with the Museum of Nature South Tyrol in Bolzano-Bozen, the MUSE Science Museum of Trento and the LMU University Munich. Over the past years, many results have been achieved: the discovery of hundreds of plant fossils and scientific analyses thereof, the recovery of a marine saurian’s bone and activities like the observation of erosion, rock shifts and displacements taking place within the streambed.
Fossil plants, shell imprints and fossil animal tracks in the Bletterbach gorge tell their stories about the flora and fauna of those times. Moreover, stones of any colour and shape tell us something about life on earth of millions of years ago:
Fire inside out – Bolzano quartz porphyry/rhyolite:
In the wake of violent volcanic eruptions, about 280-274 million years ago, hot ashes and lava streams covered the area that used to be located nearby the equator, generating the so-called Bolzano quartz porphyry/rhyolite. Today the reddish volcanic rock is part of the Etschtaler Vulkanitgruppe and constitutes the basis of the Bletterbach gorge.
From sand to stone – Gardena sandstone:
After violent volcanic eruptions 274 million years ago, heat, water and wind started their destructive work. In the course of millions of years, they washed away huge parts of porphyry rocks. Torrential streams and rivers transported fine sand to coastal areas depositing layer after layer. Stuck together by chalky and loamy material and compressed under enormous heavyweight layers positioned on top of them, they eventually created a new type of rock –sandstone. Due to the incorporation of various minerals, layers show different colour shades. Animal tracks and plant pieces were embedded in sand or mud and have thus been preserved until today, providing therefore an insight into the life of the geological past. Within these layers, we are also able to find traces of a lizard species – it is the one representing our GEOPARC Bletterbach logo.
Gypsum – the Bellerophon strata:
Towards the end of the Permian period, the land drifted away and the sea advanced. Shallow coastal waters and lagoons characterized the coastal areas, comparable with today’s Adriatic Sea in the area of Venice. The climate, however, was hotter and drier. The shallow lagoons were subject to periodical tidal changes, being dried out and then flooded again later on. In the mud of the lagoons under tropical sun, gypsum tubers were formed and are thus part of today’s layers. White and reddish gypsum strata in the gorge indicate nearby marine habitats.
The big extinction – the Permian-Triassic line:
The horizontal line between the Bellerophon strata and the Werfen Formation is coincident with the Permian-Triassic line and marks therefore the end of the Palaeozoic and the beginning of the Mesozoic (252 million years ago). Due to a catastrophic incident, for reasons that have still not been entirely clarified, most of the then existing animal and plant species became extinct within quite a short time. Experts assume that it could have been a climatic catastrophe triggered by volcanic eruptions.
A sea full of fossils – the Werfen Formation:
The Werfen Formation is composed of a variety of finely sequenced layers of limestone, marl, sandstone and argillite. Their formation dates back to the Lower/Early Triassic 252-245 million years ago, and they are thus the oldest layers of the Mesozoic. At the GEOPARC Bletterbach they are about 400 m (1,312 ft) deep, and their differences in structure suggest the interplay of periodical tidal changes. The Werfen Formation is partially rich in fossils. On the marine layers of the Lower/Early Triassic there is the only a couple of metres high Richthofen conglomerate, composed of different-sized rock pieces deposited by the rivers.
Tropical climate – the Contrin strata:
On top of the Richthofen conglomerate we can find the Contrin strata that set up the peak of the Weißhorn. Rocks were deposited in a tropical sea with shallow, clear and well-aerated waters. They were mainly formed due to the limestone-binding activity of Dasycladales algae.
