Discover the fossilized world of Festningen

Our story begins around 360 million years ago, in the Early Carboniferous. During this time the landscape was dominated by swamps and there was a warm climate of a humid character. Trees and plants grew to high and dense forests.

A tropical forest in what became today's Arctic? In Svalbard? Yes, this is true! Though hard to believe now, there were tropical forests here when the archipelago moved from 20 degrees north to 35 degrees north - this approximately where Mexico is situated today. And that is why the climate was so different and made it possible for such plants to grow high and massive.

The Carboniferous was globally known for high deposition of carbon-containing plant material - hence its name. Eventually the masses of dead plant material that were deposited formed into coal through diagenesis.

Diagenesis

At first, peat is formed out of deposited plant material. Peat is a type of soil that is very rich in organic matter, as water is pressed out of it during its formation and plant material is party decomposed already. We can see peat forming in many swampy parts of the world today - though of course not in the Arctic!

After burial, 6-10 meters of peat will be compressed to lignite and in the end to about 1 meter of coal, after a long time with high pressure and heat.

Key sources and further reading:

•  Dallmann (2015) , Geoscience Atlas of Svalbard, Chapter 6
•  Nichols (2009) , Sedimentology and Stratigraphy

Some of the dominantly abundant plants during this age were scale trees, with the scientific name Lepidodendron. These trees are an extinct order of the vascular plants, and grew up to 50 meters tall! Today we still have hundreds of thousands of vascular plant species inhabiting our world, and some look similar to the ones that existed more than 300 million years ago.

Key sources and further reading:

•  Dallmann (2015) , Geoscience Atlas

You might have never heard about a Lepidodendron before, but when you look closer at the background picture, another plant might be familiar to you.

Horsetail, in latin Equisetum, might grow in your garden or at a nearby pond. And it was also found in this landscape!

Imagine: it is a true "living fossil"! This species really existed throughout the past 400 million years on Earth!

Though we have not found any fossil exactly here at our field site, we know they were here... and are still existent in our world until today.

Unfortunately no fossils of the scale-trees nor the horsetail, and only very few other Carboniferous fossils were found at our field site in Festningen, maybe due to the reason that only little of the Carboniferous rocks are exposed, and that fossil preservation is limited in the coarser-grained sediments deposited at Festningen during this time.

Key sources and further reading:

•  Wikipedia  (Equisetum)
•  Background source  (ExtraLife)

Towards the late Carboniferous the climate changed slowly to rather arid and warm conditions. This local climate change on Svalbard was driven by the northward drift of the archipelago away from the equator. The swampy tree land turned into dry landscape with deserts, ephemeral lakes (a sort of short-term lakes), and extensive tidal zones along the coastal areas. These conditions remained similar until the mid-Permian.

Evaporites were found in many places. Evaporites occur everywhere, where water with minerals was found and evaporated into the atmosphere. The minerals stay and form often salt flats like shown in the background image. In Svalbard, this period was characterized by deposits of gypsum and anhydrite, formed due to precipitation of the minerals. This is a common process that happens when a lot of evaporation of water takes place and minerals that had been dissolved in the water, remain on the ground.

Key sources and further reading:

•  Dallmann (2015) , Geoscience Atlas
•  Mørk & Grundvåg (2020) , Festningen field guide
•  Background Source , Salt Lake, Utah

Around 310 million years ago, in the early Permian, the dry landscape reflecting an arid climate still existed. The fauna became more diverse and evolution of other animals in the water continued.

Algae, small unicellular organisms that floated in the water column, were especially common in intertidal zones and shallow, isolated bays. That is why we find fossilized algal mats at our field site in Festningen. These algal mats are interbedded with the evaporites gypsum or anhydrite and point to the existence of a warm and quite dry climate.

Those thin layers of algae were left on the riverbed when the water was retracting in an intertidal zone. Each layer in this picture above could be from only one or a few days, who knows...

Key sources and further reading:

•  Dallmann (2015) , Geoscience Atlas
•  Mørk & Grundvåg (2020) , Festningen field guide

In the late Permian, around 270 -250 million years ago, Svalbard was drifting rapidly towards the north and reached an approximate latitude of 45 degrees north. The local climate started to become colder due to this further drift to the north. It could be comparable to middle European climate nowadays. In addition, global-scale tectonic plate re-organisation shut off equatorial warm-water influx to the Svalbard area.

At this transition, Svalbard was slowly flooded and most of its landmasses disappeared under water! A deep and cold marine basin was formed that experienced strong waves and tidal currents.

Key sources and further reading:

•  Dallmann (2015) , Geoscience Atlas
•  Background Source 

The ancient sea life consisted mainly of rather small marine animals that lived either on the seafloor, or swam or drifted in the water column.

Below you see a selection of bryozoan imaginary drawings that lived underwater. They lived attached to the ground or rocks, usually in colonies and some similar species are still abundant today.

Key sources and further reading:

•  Mørk & Grundvåg (2020) 
•  Dallmann (2015) 

Since the climate and so the water was cooling down, the animals that lived there had to adapt to cooler waters. Over long time, certain animals, such as sponges, enriched their skeletons with silicates. The silicate, that was found in the spiculites, the spikes of the sponges, stabilized the skeletons better than calcite, which is more common in warmer waters. Therefore, this is one remarkable, significant adaptation to the cooling environment and gives today`s scientists hints about the temperatures of ancient environments.

During the sediment burial and diagenesis, the silica of the sponges turned into chert- a very hard rock , that is resistant to weathering (erosion by weather). Those layers usually form cliffs in todays Svalbard landscape.

Key sources and further reading:

•  Beauchamp & Baud (2002) 
•  Mørk & Grundvåg (2020) , Festningen field guide

Also crinoids and brachiopods were found at our field site at Festningen. Brachiopods consist of two hard shells and a soft tissue foot, and were abundantly found especially in Permian layers at our field site. They are among the most important marine fossils.

Those fossils were embedded in limestones, that are formed in carbonate-rich environment and are another hint for the extended marine environment at that time at Svalbard.

Key sources and further reading:

•  Mørk & Grundvåg (2020) , Festningen field guide
•  Carlson (2016) 

At the end of the Permian age, around 250 million years ago, something severe in Earth`s history happened! A sudden extinction of most species living at that time was observed nearly all over the world in these layers: the biggest mass extinction ever on Earth occurred at the Permian-Triassic border. The cause of this mass extinction is not entirely clear to the scientific community, but is often attributed to huge volcanic eruptions in Siberia. These eruptions caused CO2 and SO2-enrichment in the atmosphere, and big amounts of acid rain affected both life on land and a change in the acidity in waters. This sudden change to a hostile and toxic environment meant the end for the big majority of living species: Approximately 95% of marine and 70 % of the terrestrial existing species died out in just a "moment" of Earth history!

Key sources and further reading:

•  Knoll et al. (1996) 
•  Zuchuat et al., (2020) , Deltadalen P-T drilling
•  Background source 

In the Lower Triassic, Svalbard lay at a latitude of approximately 40-50 degrees north, and a pronounced change in climate happened also on Svalbard. The hot and dry climate conditions changed to a sub-tropical to temperate climate. 

The rock layers immediately above the Permian – Triassic boundary at Festningen show an absence of fossils or traces of life - this still marks the major consequences of the Permo-Triassic mass extinction.

But still, a new era of species started. The mass extinction created living space for those species that survived, and new ones that evolved to fill the space. The survivors developed and adapted themselves to new environmental conditions and took over the space left by the species that died out. At the same time new species evolved and spread successfully. By the Middle Triassic flora and fauna were recovered, though of very different composition than before the mass extinction.

Deposits in Svalbard including at our field site Festningen were dominated by organic-rich mudstones. Eventually towards the late Triassic, marine deposits and life were replaced with sandy deltaic deposits with abundant flora, that came, amongst others, from the Ural mountains.

Key sources and further reading:

•  Dallmann (2015) , Geoscience Atlas
•  Background source 

For geologists, ammonoids are important index fossils. An index fossil has usually a wide geographical distribution and is distinctive for a certain span of time in Earth's history. When an index fossil is found in a certain layer of rocks, it therefore can be easier used to determine the historical time of geological layers.

Also ammonoids were used for dating rock layers, because different species were distinctive for different periods in Earth's history. Overall, ammonoids were abundant from Triassic until end of Cretaceous. But species looked quite diverse. One very distinctive characteristic are the septa, the dividing walls that separate the chambers of the hard shell body, as seen below.

In Middle Triassic layers we find an ammonoid at our field site. Suture lines are difficult to notice on the photo below.

Key sources and further reading:

•  Dallmann (2015) , Geoscience Atlas
•  Wikipedia 

Now we are entering a long tropically warm and humid period of time in Earth's history. In Jurassic, we are 210- 145 million years back in time, and it was an important period of the animals history: it was showtime for the real big animals!

Huge marine reptiles evolved during this period of time and found in rock layers of these early Jurassic times. Students made a spectacular discovery on Svalbard in 2001, not very far from Longyearbyen. A number of ancient bones were found at Janusfjellet by accident. Three years later the biggest serious excavation on Svalbard started at that point. Jørn Hurum and his team spent the next decade systematically exploring for clues to decipher the past ecosystem. Two different big marine reptiles were discovered, and many of them were distributed in a quite small area.

Key sources and further reading:

•  Svalbard Museum Exhibition 
•  Dallmann (2015) , Geoscience Atlas
•  Background source 

The plesiosaur was a huge marine reptile that existed from Triassic to Cretaceous. It could have looked like a sea monster indeed, with up to 13 m in length, a long neck and huge, sharp teeth. Not a friendly beast to meet up when you are taking a swim in Isfjorden today!

The Ichthyosaur that was excavated in the same area as the big plesiosaur. It was found mainly in Triassic and Jurassic and only rarely in Cretaceous. This dolphin-like reptile was up to 4 m long and feeding on fish and squid.

Key sources and further reading:

• Read more about fossilized marine reptiles  here .
• Another interesting publication on " Monsters of the Sea ".
• Learn about a found of a fossilized pregnant ichthyosaur  here .
•  Delsett et al. 2019 

Also other small and strange looking animals swam in the water column during that time. They were called belemnites and looked almost like little squids...

Belemnites were abundant in the seas from Triassic until Cretaceous times. Imagine... that means they survived on Earth for about 190 million years!

These little organisms of just a few centimeters size, most likely formed one important basis of food for many of the big reptiles in the marine environment.

Key sources and further reading:

•  Delsett et al. 2019 

Also fossils of bivalves and gastropods were abundant in the same rock layers. Successors of the same family are still existent nowadays, and look similar.

All those marine animals are evidence for the existent marine environment during that time at Svalbard.

Key sources and further reading:

•  Mørk & Grundvåg (2020) 

Now we are in a new quite "motional" age for the Svalbard archipelago. Remember, by the end of Triassic, Svalbard was a deep marine basin, with only a few parts of land forming as major sandy deltas prograded across the Barents Shelf.

In marine waters, ammonites existed throughout Triassic, Jurassic and Cretaceous. The popular example shown below was not found at our field site at Festningen, but not too far from Longyearbyen in rocks of Jurassic age.

Also the fossilized brittle star is part of the marine Cretaceous fauna.

Key sources and further reading:

•  Background source 
•  Dallmann (2015) 
• University of Oslo, Hans Arne Nakrem

In the first million of years of the early Cretaceous, oceanic crust started to form in the Arctic Ocean. Huge masses of magma were pushed up from the seafloor and also Svalbard was slowly lifted up! After this quite long period of uplifting, the archipelago was over the sea level again and land was visible!

The landscape slowly started to looked already similar to what we find in our recent world. The marine basins from before disappeared and trees and other plants spread and evolved in this tropically warm environment. New species evolved from primitive plants from earlier times and formed an important food basis for new and old animal species, among them many of the biggest organisms that ever lived on Earth up to now!

Imagine, a dinosaur is walking along a beach and leaves its footprint in the sand...

Yes, this is exactly what we find at our field site! These fossilized footprints of a dinosaur were found at the beach of Festningen - and they were left also on a sandy beach millions of years ago...

Key sources and further reading:

• Read more about dinosaur footprints found in Svalbard  here .
•  Background source 

Researchers found rootlets of plants in several layers and surfaces, that are aged to Cretaceous times at our fieldsite at Festningen. These roots are visible as vertical tubes, that are filled with sandstone, or as black, carbon-bearing branches extending downwards.

Key sources and further reading:

•  Mørk & Grundvåg (2020) , Festningen field guide

In addition, the findings of sandstone bed deposits with wave-ripples with crests are strong hints for open marine waters and tell the scientists about stormy climate conditions in the Cretaceous era.

Key sources and further reading:

•  Mørk & Grundvåg (2020) 

The next rocks preserved in Svalbard are of Paleogene age - including the coal-bearing rocks that form the basis of all permanent human settlements in Svalbard as these are (or were) mined at Longyearbyen, Ny Ålesund and Svea, and Barentsburg (just east of Festningen).