What are Fossils?
The Museo Zardini of Geology in Cortina d’Ampezzo is one of the best places in the Dolomites where to acnowledge oneself with the dramatic geologic history of the area, and also where to admire an outstanding collection of fossils.
But what justifies the presence of some 20,000 fossil specimens – belonging to 1,000 different species – in a museum?
On the planet there exist – or have existed – living beings that have peculiar traits, and certainly fossils are among the most extraordinary. They are unique creatures, in that they managed to survive through time beyond the limits of their natural life span.
Fossils have been able to leave petrified traces of their existence – or at least an impression of it. For this to occur, however, two conditions were necessary; first of all, the ‘lucky’ circumstances of dying in a place where the organism was protected from one of its worst enemies: air (and good insulating material are, for instance, drops of plant resin, thin marine mud sediments and volcanic dust).
The second condition that favoured fossilisation was the presence of hard parts resistant to attacks from the outside – such as shells, bones or carbonised tree trunks.
What Good Are Fossils?
Fossils not only tell us about how such living creatures looked like and how they behaved in a far-off past; they also provide experts with lots of valuable information, and allow them to obtain an idea about the climate, environment and the period in which these organisms lived. It is thanks to the fossils, in fact, if we now know that the Dolomites were not always the mountains we see today.
Starting 234 million years ago, various types of enviroments succeeded one another: tropical coral reefs rich in animal life, deep ocean plains composed of red mud, beach and coastal plains inhabited by large bivalves all created the ideal living conditions for strange, spiral-shaped animals known as ammonites to appear.
In the museum, the layout and the detailed panels intend to facilitate the illustration of how these environments followed one another during the course of the various geological eras: each period had its own particular fossils, on display in the different sections, while the typical rock formations are shown in photographs.
The history of the evolution of our planet and of life on Earth is certainly one of the most fascinating aspects in the natural sciences – as well as an amazing enigma in itself.
Particularly interesting, in this regard, is the period between 234 and 65 million years ago, known as Triassic, during which the layers of rock found today in the Cortina d’Ampezzo basin (Conca d’Ampezzo) – and surrounding areas – were deposited.
These rock strata contain a wealth of fossils – traces of the incredibly prolific and diversified life forms that characterised this period in the region.
Most of these fossils are now also labeled as Triassic – in that they take their name from the geological period bearing the same name, but in fact many of them span also the length of the Jurassic and Cretaceous periods, thus covering the whole of the Mesozoic era.
Believe it or not, during that time the Dolomites were more or less located at the Tropics, on the western edge of a large marine gulf that penetrated into a supercontinent now known as Pangaea.
This sea, called Thetis, was warm, clear and suitable for the growth of reefs separated by water straits – some deep, others less so – in conditions similar to those that can be found today in the Maldives archipelago, the Caribbean or the Great Coral Reef of Australia.
Let's now look in more detail at the various geological periods (and related rock types), as they are represented in the museum.
Sciliar Dolomite and Buchenstein Group
At the end of the so-called Anisian stage, about 234 million years ago, in the area around Monte Cernera – to the south of the Ampezzo basin – there was an atoll surrounded by the sea that became increasingly deeper in the direction of Cortina.
Various types of fossils were found in those rocks, pointing to different environments; amongst these, were the ammonites – creatures that lived in the deep sea around the atoll – and other organisms that created the atoll itself (algae, brachiopods, large and small bivalves, gastropods and sea anemones).
The discovery of ammonites, particularly, was of great scientific value: as these are animals that evolve in different and unique forms, through them it has in fact been possible to reconstruct a precise geological time frame for that period.
As far as the organisms that created the atoll are concerned, their presence and subsequent disappearance would seem to point to the fact that the atoll, after an initial stage of growth, had slowly and gradually started to sink.
Wengen Group - La Valle Formation
During the Upper Ladinian stage, around 230 million years ago, in some parts of the sea located west and south of the Ampezzo basin, volcanic eruptions began to occur, with the subsequent formation of islands.
Following the erosion of these islands, dark deposits – known as volcanoclastics – were produced. In these rocks, besides marine organisms (Lamellibranchia and ammonites), important plant fossil remains were found, indicating that tropical forests grew on some of the lands above sea level.
San Cassiano Formation
At the beginning of the Karnian stage, some 229 million years ago – when volcanic activity had ceased – in the Ampezzo basin and surrounding areas a relatively deep (300-500 m) tropical sea environment was recreated, dotted with coral reefs just below the water surface.
In this tropical sea – reconstructed in a simplified manner in the museum – calcareous mud and deposits of various types built up, including algae, single corals, shells (Lamellibranchia, gastropods, cephalopods, brachiopods), sea urchins (Echinoids) and sea anemones (Crinoids).
These deposits, which subsequently produced soft rocks like marl and marly limestone as we see them today, are now collectevely known under the name of San Cassiano Formation.
The volcanoclastic particles, carried by underwater currents and landslides, built up against the escarpment of Monte Cernera, to the south of the Ampezzo basin: a mountain which is like an open book where to observe many of the geological phenomena that contributed to the creation of the Dolomites.
Volcanoclastic particles were then buried and fossilized within the reef, thus retaining their original shape; of that reef, the escarpment and underwater slopes connecting the barrier itself to the sea bottom are still identifiable today. These slopes of white and grey Dolomite rocks continue in fact to stand out against the darker deposits of volcanoclastics.
The eastern and south-eastern faces of Col di Bos and Sotecordes are another typical example of rock formation within the Dolomites.
The section to the left of this mountain range is made of Horst and crystalline rocks, and documents well the presence of the former coral reef; on it, living organisms such as algae, calcareous sponges and corals proliferated.
Alongside the coral barrier, towards the more open sea, an escarpment formed mainly by detritus extended. The reef was broken off by the waves, and this is represented today by boulders and smooth rock faces.
At the end of the escarpment and at the bottom of the open sea – corresponding to the fields and woods to the right of the mountain – particles and shells continued to deposit the organisms that went on to form what we identify today as the rocks and fossils of the San Cassiano Formation.
A Wealth of Life Forms
Gastropods are mollusks with a spiral-shaped shell from which a well-developed fleshy foot protrudes, helping them to move about; they also have a head with tentacular eyes.
Many fossils have been found with traces of their shell and of the original colours; an actual descendant of the gastropods that has made its home on land is the snail.
Brachiopods, on the contrary, have a fleshy body enclosed between two valves – one dorsal and the other one ventral. They only live in the sea, anchored to the bottom by a muscular peduncle dug into the sediment.
Brachiopods fossil specimens always have their valves half closed, and are different from other shells inasmuch as their valves differ from one another. They can also be recognized by the peduncle hole. A typical modern-day representative of brachiopods is the Lingula, which still digs its home in mud sediments.
The Lamellibranchia, or bivalves, also feature a fleshy body enclosed by two valves; they can live either anchored to the sea-bed or free. In fossil deposits, they are most commonly found with their valves separated.
Typical modern-day representatives of these mollusks are the Venus clam and the mussel; in fact, the brachiopods and the Lamellibranchia mostly differ from one another in regards to the symmetry of their valves.
Echinoids, better known as sea urchins, have a central skeleton consisting of thin tests and spines of various shapes: club-, column-, spatula- and needle-shaped. The spines and thin tests of the skeleton can be found fossilized in the rocks.
Crinoids have a fleshy body enclosed in a cavity – called calyx – out of which tentacular arms protrude; the calyx is supported by a long peduncle anchored to the sea-bed, and through its centre passes an elementary nervous system. The calyx consists of interlocked plates, while the peduncle is composed of superimposed discs of diverse shapes and designs; both elements are found fossilised individually or in groups.
Cephalopods have a spiral-shaped shell spilt into chambers by membranes called partitions. While the fleshy body lives in the outer chamber, the other chambers are full of gas; by varying the amount and pressure of gas in the chambers, the organisms are able to move horizontally and vertically in the water, like small submarines.
Cephalopods are split into ammonites and nautiloids: the ammonites became extinct 65 million years ago (at the beginning of the Tertiary era), while nautiloids can still count on a living representative - the Nautilus.
Sponges – which, together with corals, are reef-building organisms – also live anchored to the sea-bed. They eat by taking in nutritive particles from the water through numerous little holes, still visible on fossil samples.
Corals, though, are the major reef-builders: they normally live in colonies, and each single animal – called polyp – makes its home in a cup-shaped theca.
The most obvious difference between fossil samples of sponges and corals is that – in the case of the former – a globular or extended theca can be observed, distinguished by lots of little holes, while the latter feature radial partitions that split up the theca.
During the Karnian stage, 225 million years ago, the Dolomites’ landscape was heading towards a drastic change caused by a sudden drop in the sea level, with the consequent emergence of large land areas – especially towards the south of the Ampezzo basin.
The coral reefs had disappeared once and for all; flat and extensive sea-beds were now taking shape, covered by very shallow water (just a few inches), generally murky due to the movement of the waves. The nearby dry lands were covered in forests.
The sediments that deposited in these environments often contain fossils of large bivalves (such as Trigonodus, Myoforia, Pachycardia, Ostrea), sometimes the fossilised teeth of fish, and rarely the bones of land reptiles; the remains of plants – mainly conifers and Equiseta – are also found in the form of coal or drops of fossil resin: amber.
This amber is among the oldest in the world; in most cases, the droplets are small in size – from just a few millimeters to a few centimeters. Many are also cracked, due to the strong pressure of the fossilisation process; some even contain microscopic inclusions of pollen, ashes and vegetable fragments.
During the Norian stage, 224 million years ago, a general increase in sea levels resulted in large land areas (tidal plains) being periodically covered by the sea – as is the case today for a number of islands belonging to the Bahamas archipelago. In this environment, the Main Dolomite deposits began to form.
A typical feature of the Main Dolomite is its cyclic nature, which can be appreciated by observing the rock faces: these consist of very regular layers, indicative of events that occurred cyclically.
By carefully observing each single layer, we cannot help but notice that these consist of two parts: one is densely laminated, and corresponds to carpets of fossilized algae, while the other is thicker and consists of calcareous mud transformed into rocks which contain the internal models of bivalves – the Megalodonts.
These cycles were then repeated dozens and dozens of times due to a lucky concurrence of circumstances, amongst which was a slow but constant lowering of the sea-bed (subsidence). By upsetting the deposition of mud and the growth of the carpets of algae, this resulted in the water remaining shallow throughout the region.
The repetition of these cycles for about ten million years produced an accumulation of up to 1,000 metres of deposits, which today form the magnificent rock faces around Cortina.
The landscape of that time can be imagined as a large expanse of shallow water populated by algae prairies (Poseidonia alpina). By trapping the carbonate mud suspended in the water, the algae then created hardened crusts – called stromatoliths – currently identifiable in the rocks in the form of thin laminations.
These tidal plains, broken up by canals and small stretches of water, gradually became submerged shallow sea-beds as they approached the sea, consisting mainly of carbonate mud. Here lived colonies of mollusks famous for their shapes and often of very large size: the Megalodonts.
The coastal areas linked with the dry land were also sporadically inhabited by a number of species of dinosaurs, fossil traces of which have been found on the surface of Main Dolomite layers in various localities scattered around the Ampezzo basin.
Dachstein Limestone and Grey Limestone
At the end of the Triassic period, 210 million years ago, a new sudden lowering of the sea-beds transformed the entire area from a tidal plain (mostly composed of Main Dolomite) into a tropical shoal constantly covered by water and similar to the present submerged platform of the Bahamas.
The climate also changed, from dry tropical (affected by the vicinity of dry lands) to wet tropical – more typically marine conditions. The innermost parts of the platform were distinguished by calm waters where carbonate mud deposited.
Conditions in the outermost parts of the platform, though – in locations nearer to the open sea and subject to the more direct action of waves – favoured the formation of sandy underwater dunes.
Moreover, thanks to the existence of clear water, constantly agitated and therefore rich in nutrients, various organisms thrived, including numerous colonies of brachiopods: all three types of deposits, subsequently transformed into limestone, today represent the succession of Dachstein Limestone, Grey Limestone and Fanes Encrinite.
Then, about 185 million years ago, in the Mid-Jurassic period, the platform of limestone deposits suddenly dropped even further, due to the sea-beds sinking for over 1,000 metres; this created a submerged plateau swept by ocean currents that did not permit the accumulation of deposits of any substantial thickness.
In this environment lived large mollusks, with spiral-shaped shells similar to the Nautilus, and now extinct: the ammonites. Due to the discovery of numerous fossil shells of these creatures, and the red colour of their deposits, this type of rock has been termed Ammonite Red (Rosso Ammonitico in Italian).
Marne del Puez
Between 131 and 65 million years ago, during the Cretaceous period, various sediments were deposited that have been grouped together under the collective name of Puez Marls (Marne del Puez in Italian): these are friable and easily eroded rocks that produce rounded shapes, now visible on different mountain plateaus.
Such deposits accumulated in a deep-sea environment; they prevalently consist of microscopic shells of plankton and numerous ammonite cells showing a genetic mutation in the shape of spirals, which tend to unfurl and open.
They also contain fine particles of clay and silt, as well as sand-grain pebbles pointing to the arrival of detritus from the erosion of the first mountains of the Alpine chain, which were already beginning to form under the sea.
Monte Parei Conglomerate
These are the youngest rocks of the Dolomites and date back about 25 million years ago, during the Tertiary era. They consist of rounded pebbles of various size and nature, mixed with sands and the remains of shells, algae and sharks' teeth; collectively, they are known as Monte Parei Conglomerate.
The environment in which these rocks took shape can be imagined as a rather rough coastline with steep cliffs soaring high above the sea, interrupted only by small valleys along which torrents carried detritus, thus creating new sections of beach.
The Monte Parei Conglomerate was deposited horizontally at the valley mouths and on the sea-beds; then it tilted, and it now consists of vertical strata.
These vertical layers indicate both the deformation of the rocks in a period before the conglomerate was actually deposited, and the beginning of the great upheaval that would later result in the creation of the Dolomites.
The Archaeological Site at Mondeval de Sora
At the head of the Val Fiorentina – a rather narrow Dolomite valley that abruptly opens onto a plateau of open meadows, disseminated with springs and large limestone blocks between Corno Alto and the Lastoi de Formin – lies the large, flat basin that hosts the important archaeological site of Mondeval de Sora.
This is where, in 1986, at an altitude of 2,150 metres, underneath an isolated rock that fell off the Lastoi de Formin during the last glacial period, a settlement came to light dating back to the Castelnova Period, which for the first time provided archaeological evidence of the daily life of high-altitude hunters who lived between the end of the Mesolithic and the beginning of the Neolithic periods (7-8000 BC).
The most important artifact to be discovered was the burial site of a man aged about 40, a little over 1,7 m tall, buried face upwards with his limbs stretched out and feet resting on a stone.
A pile of tufite and marl blocks covered his lower limbs as far up as his pelvis. The body would seem to have been buried wrapped in an animal skin, closed by means of two drifts; the position of the left hand – vertical and with fingers slightly bent – would seem to point to his having once held something.
Alongside the body were items of clothing (deer canines, presumably forming a necklace), blades and pieces of flint, bone tools. The flint undoubtedly came from the hillsites used during the winter and abandoned during the summer to climb to higher altitudes in search for food.
These migrations made it necessary to camp higher up in the mountains, on relatively flat lands, where there was plenty of water supply available. Mondeval appears to be just one of such camping grounds, and the artifacts from this find are now kept in the Selva di Cadore Ethnographic Museum.
The Mesolithic Period
Until 1968, traces of the Mesolithic period were reputed all but absent in Italy. That year, however, at Vatte di Zambana near Trento, in Trentino, a Mesolithic settlement was explored, and the first Italian burial site dating to this period uncovered; later on, other Mesolithic sites were discovered.
These were found in valley bottoms or on plateaus, but no one thought of looking for them at an altitude of 2,000 metres! The initial discovery dates back to the summer of 1971 at Colbricon Lakes, near Passo Rolle, at an altitude of about 1,925 metres, where the first Mesolithic flints to be found at such a height were uncovered.
This was to be the first of a series of finds which, from Trentino, spread further afield thanks to the use of systematic methods.
The sites which were found later are normally located between 1,900 and 2,000 metres of altitude, in flat and open country, rich in water. They were mostly summer camps – therefore inhabited only temporarily – located at the edge of woodland and alpine pastures.
The reason why the hunters, who spent the winter in large valley floors, climbed to these heights has been unknown for a long time; it was generally assumed that they were attracted by the abundance of large mammals to hunt (wild goats, chamois), but there were no archaeological finds to support this – that is, until the site at Mondeval de Sora came to light: a discovery that even made it possible to identify the prevalent hunted species (deer).
Rinaldo Zardini: the “Eternal Child” who Dedicated His Life to the Mountains
Finally, I think it as an apt conclusion to spend a few words on the man himself – Rinaldo Zardini, to whom this museum is dedicated.
Zardini was born in Cortina in 1902, and carried out his eclectic secondary education in Zurich, where he studied natural sciences as well as learning three languages and to play the piano.
In 1920 he returned to his home town to join his father's photo-optical company (still existing!), where he acquainted himself with photographic techniques – a skill that was to become very precious later in his life.
This period marked also the beginning of his activities as a naturalist: in 1922, Zardini started a herbarium of plants from the Ampezzo basin; this work was completed 15 years later, with the identification of some 1,000 species. During that time, he also started to collect insects and butterflies.
However, the major contribution given by Rinaldo Zardini to the Natural Sciences – and that for which he will always be remembered – is as a paleontologist.
It all began in 1935, when he was intrigued by a strange stone he saw in the Boite river bed. He collected it, and we now know it was a fossilized coral – a discovery which excited Zardini tremendously, and that was to change his life.
His research took off from there – especially on the San Cassiano Formation layers of the mountains around Cortina. He ended up collecting an incredible quantity of fossils (over one million specimens, it seems!), which earned him the respect of fellow paleontologists around the world.
Without any knowledge of chemistry he observed that, over time, the humic acids tend to destroy the compact calcite matrix around the fossils – especially in coral, sponges and mollusks – without affecting the actual fossils in any way.
Extremely rare and beautiful specimens thus remain hidden, until they reemerge in all their glory after cleaning.
Little by little, through publications of his own and in conjunction with specialists the world over, he attracted widespread attention to his collection of Lamellibranchia, cephalopods, gastropods, sponges, sea urchins and bivalvia – all of which appeared to have no more secrets for him.
Thanks to the spectacular variety of specimens in his collection, Zardini prompted researchers from all over the world to address again the problem of the San Cassiano fauna.
The importance of his contribution is so great that, later in his life, Rinaldo Zardini was appointed affiliate researcher of the Smithsonian Institute in Washington.
His work was acknowledged also at national level, and he was granted a honorary degree by the Faculty of Natural Sciences at the University of Modena.
Zardini dedicated his life totally and wholeheartedly to the mountains and the treasures they conceal. He lived his dream to the full – like an eternal child, which he remained until the end of his life in 1988.
Most of the specimens he collected, now all carefully catalogued, are on show in this museum, which opened – thanks to his bequest – in 1975.
The museum has recently been moved from its historical headquarters in the centre of Cortina to a new, more spacious location just outside the central pedestrian area, in Pontechiesa, not far from the Olympic ice-rink.
I think it would be a good idea to finish with some words by Zardini himself, which mark the very beginning of his lifelong passion, and still betray the vivid emotion of that moment:
“In 1935, quite by accident, I came across an unusual stone in the Boite riverbed. I put it in a cupboard and asked everyone what it could be.
An English botanist told me it could only be a piece of fossilized coral.
This made me all the more curious.
For months, I moved from one valley to another to find the place where the coral could have come from.
Then, one autumn day, I sat down at the foot of the Faloria to rest.
When I looked on the ground, I found myself surrounded by Lamellibranchia, ammonites, and many other fossilized organisms.
It was like being stranded on a sea shore: all the fossils were in good conditions, as if somebody had taken care of them. Corals and sponges seemed to have just appeared out of a tropical sea ... ”
Copyright © 2012 Italy-Tours-in-Nature