Fossils from Denmark (part 1)

By Niels Laurids Viby

Denmark – why on earth should anybody in the UK go to such a strange place – where people, among other things, drive on the wrong side of the road and speak a funny language? And why write something for Deposits on the subject at all?

You can find fossils from almost every time period apart from a few in the UK. For example, you can find them from the very top of the Cretaceous period (Maastricien) and the Lower Palaeocene period (Danien). However, these particular geological periods, especially the Danien that was, after all, named after a site in Denmark are also found in many places in Denmark. Moreover, at one site, you can actually access the KT border and get a sample from the famous (but thin) band with high concentrations of iridium.

Of course, most fossil collectors concentrate on what is found close to home, and for good logistical reasons. However, for those who want a broad collection covering the development of life or for that matter a mass extinction, a holiday in Denmark is a good option for filling a gap without having to drive long distances – Denmark is a rather small country!

In this first article on Danish geology, I will provide the reader with two things. Firstly, a short description of Danish geology, including what is legal to collect and what is not and secondly, a description of a Danish speciality – Lower Eocene diatom clay, the ‘moler’, which can be very fossiliferous. This will be of interest for people who collect from the London Clay.

Danish geology – a simplified outline

The surface of Denmark consists of ice age deposits – everywhere! And, even if you can find the odd fossil (normally a flint internal cast from a sea urchin) just lying in a field, this is not always very interesting for a fossil collector. To find fossils, you will need to get into a quarry (in Denmark, many allow fossil collectors in at the weekends and some even on work days), a gravel or clay pit (which, with only one exception, are privately owned, so permission is needed) or collect from a beach in front of cliffs. Denmark has a VERY long coastline, so the latter is an option that many local collectors take, especially those who have kids who can play on the beach while mothers do some serious fossil collecting – more than 50% of the members of fossil clubs are females in Denmark.

As to the deposits below the glacial till, Denmark can be separated into two very different parts. Firstly there is the island of Bornholm (located in the Baltic Sea, south of Sweden), which is 75% Upper Cambrian granite, 20% Cambrian sandstone without fossils, with the remaining 5% being interesting for fossil collecting. This can be carried out at a few sites that contain Mesozoic fossils, including a few Cretaceous sites and a few Jurassic sites. But, compared to UK, few fossils are found on Bornholm.

Secondly, there is the rest of Denmark (Jutland, Fyn, Zealand and the minor isles) that is tilted, with the result that, going from north-east to south-west, you pass from a portion of Upper Cretaceous (Maastricien) into Miocene layers. However, only in a few places can this be accessed:

• Cretaceous layers can be visited at Zealand and the island of Moen to the south of Zealand. In north and north-east Jutland, the best site is fenced but organised groups can normally gain access during weekends, after prior permission has been obtained.

• The Danien (Lower Palaeocene) can be visited at Zealand or in north and northeast Jutland. There are a number of accessible quarries and a lot of coastline locations to visit.

• Deposits from the Thanetian (Upper Palaeocene) are not common. However, the best site is at Fyn, but it hasn’t many fossils as the shells of snails and bivalves have dissolved. As a result, local fossils collectors work a lot with liquid rubber to produce casts of fossils.

• Eocene deposits can by found in several places in Jutland. A good site is Trelde Naes, north of Fredericia on the east coast, a site that is very similar to the Isle of Sheppey, with the exception that this site is hard to visit. To examine the deposits, you have to climb a fallen tree or risk getting stuck in sticky clay. In fact, part of the beach is used by the military for rough training of recruits! However, it is interesting in that the species found at this site are different from those you find in UK, an example of this being the crabs. The nine species from Denmark are all different from the species found in similar looking nodules at Sheppey. So Trelde Naes might be worth a visit for a keen Sheppey collector, despite the access difficulties.

• The diatom ‘moler’ (see below) is found in the western part of the ‘Limfjorden’, mainly on the Islands of Mors and Fur. This formation starts at the top of the Palaeocene, with the main part in the Lower Eocene.

• Oligocene deposits are found in the north and central part of Jutland and at some sites in the central part of the east coast of Jutland. In some places, it is possible to find nodules with rather large crabs, even if they are pretty rare nowadays. The sites are now sadly over-collected.

• Finally, the Miocene is only accessible at a ‘Geosite’ adjacent to a small museum at Gram in the south part of Jutland. It costs £2.50 to go to the site to search for fossils, where you have to dig into solid clay and it is hard work.

Fossil collecting and Danish law

In Denmark, fossils ‘of exceptional interest for science and/or exhibition’ have to be presented to a museum. Every year, some 20 fossils are declared museum property, but when that happens, the finder will normally get a copy of the fossil and be paid a fee, going from (normally) a few hundred pounds to, in rare cases, £2,000.

The chances are that you will only find fossils that can, in fact, be kept. However, should you stumble over a bird skeleton in the diatom ‘moler’, it definitely goes to a museum! (There have only been three of these found during the last hundred years, so don’t fret. You’ll probably not find one anyway!)

Fossils from the ‘moler’

The ‘moler’ (mo is an old local word for ‘white’; ler is simply ‘clay’) is found in a number of cliffs in the west part of the Limfjord and in a number of quarries. In fact, it could be described as the Danish equivalent of the Green River Formation in Wyoming, USA.

An interesting feature in Denmark is that the quarries are very positive towards fossil collectors – just stay away from machines! As a matter of fact, the museum located at Mors is dedicated mostly to a collection of fossils that, over time, have been found by people working in the quarry, spending precious work time saving fossils. Even today, the Museum is, to some extent, financed by Skamol, the factory that turns moler into products similar to bricks (but very light – they can float) and highly absorbent materials, for example, cat litter.

Even if the moler quarries and some of the cliffs (Hanklit at Mors should be visited) are impressive, they are not base rock, but giant flakes that have been transported by ice from a location in the north and then dumped and folded during the last glaciation. In fact, moler is found in some of the test drills for oil in the North Sea, including the odd fossil

The moler was deposited in a subtropical sea at a threshold in a seaway that, every now and then, was exposed to conditions lacking in oxygen (anoxia) that caused the deaths of living organisms. In these situations, beautiful fossils were created. At other times, small bits and pieces of dead fish debris covered the floor of the sea. This you will encounter again and again when splitting rocks, as these layers are less coherent than the moler. (Complete fishes do show up every now and then.) The bioturbated moler is full of traces from burrowing animals, but is generally without fossils of the animals that made them or, indeed, any other animal.

As implied, most of the moler consists of diatoms, with a variable amount of clay and other materials: the yellow colour is of course caused by iron. Soft moler can be rather featureless (being heavily bioturbated and normally without any fossils) or it can be laminated. The latter variety is easily split with, for example, a palette knife. Unfortunately, this material is very fragile. Plates with specimens have to be wrapped in soft paper and stacked tightly in boxes so they stay in position for transport. It can be a good idea to air spray them with a fixative when at home or (if they are dry when collected) at the site.

One special feature of the moler is the black or sometimes grey/white bands that can be seen interbedded within it in the quarries and at the cliffs. These are ashes from volcanoes that were located somewhere near the Faeroe Islands. There are, all together, 179 dark bands that have been given numbers, from –39 to -1 and from 1 to 140: layer 0 is missing, for reasons only known to the (now departed) creator of the numbering system! If fossils are found in situ, the bands can be used to specify the exact location relative to the numbered ash layers.

The very lowest part of the formation has a high content of black clay and is normally hidden. Sometimes, it can be seen in one of the cliffs at Fur. It is much laminated and includes hardened layers that can contain numerous fossils. The lower half of the rest of the formation is rather uniform with few ash layers. It is this that is worked in the quarries. The upper part has numerous ash layers that are close together, making it less usable economically. A lot of the material found in the waste piles seems to be from here.

Another speciality of the moler is large concretions with a high content of calcium called ‘cementsten’ – that literally translates as ‘concrete stones’. These are very hard and you will need a heavy-duty hammer to split them. Fossils found in cementsten (often insects) are extremely durable in contrast to the fossils from the soft moler. However, not as much detail is preserved and, for that matter, they are not as good looking.

Where to find the fossils: directions

You should start at the city of Skive. Here you have two options. Firstly, you can go north to the island Fur. At Fur, you can start by visiting the local museum to look at fossils from the moler. Then, if you ask for directions, you will probably be guided to at location called Knudeklinterne at the north-west corner of the island. If you have lots of time, you can go there, as this is an impressive example of a costal moler cliff and a site where most of the ash layers are present.

However, as the rate of erosion is slow (‘Limfjorden’ is, after all, a small inland sea) and because many tourists visit this location, the chances of finding any fossils are rather small. In general, searching the beaches below moler cliffs can result in finding fossils, but it is better to go to a quarry.

Therefore, you should go instead to the north-east towards Rodstenen. After travelling on gravel roads for a kilometre or two, you come to a Stone Age burial on top of a small but steep hill. Just before this, there is a road with a sign showing a beach suitable for bathing. Follow this for some 500m down through some trees and then the road goes through a major quarry.

At the left side of the road, there is a flat area used for parking in front of a tall cliff wall of moler. On the right hand side of the road is the entrance to the active quarry. Go in here and find a pile of material. Now, you only have to start splitting moler and cementsten and sooner or later you will find some fossils. (A rule of thumb: when you want to go home after spending ages splitting some 1,317 rocks, at this point, you should stay another hour or two. The shrimp and the leaf pictured in this article were found this way. Nothing was found for three hours, but then they suddenly appeared!)

You can also go north-west from Skive towards Nykobing Mors/Thisted. After some 25km, you pass a bridge (with an enormous concrete fender border blocking the view) and then you are at the island of Mors. Follow the road some 5km more and turn right towards ‘Feggesund’. After 17km, a sign reads ‘Molersmuseet’ to the left. Drive 500m and you will find yourself at an old farm building (the second on the right) where you can go in to see a collection. This collection is different from the way those in many museums are set up. The curator (who is often is there – a man called Henrik Madsen with red hair) has set up an impressive assortment of what can be found, but it contains not only the rare fossils but also the common fossils that you may find later.

At this museum, you have several options. Just opposite the parking area at the museum is an old disused quarry with impressive ash layers. It is worth looking at, but you will probably not find any fossils. 200m to the left of the museum parking area, down a paved road is another quarry. At the present time, this is being used for dumping waste materials. However, as this includes cementsten, you can sometimes find some of these. And, if split, you have a decent chance for finding insects. If laminated moler is around, you also have a good chance of finding small fishes and, if you are very, very lucky, an impression of a small Eocene bird. In any event, on a good day, many fossils can be found.

At the present time (late 2007), the local factory, which is located a kilometre north of the museum, is supplied from another quarry. From the parking area, you should go right 100m on the paved road and turn left onto a gravel road to this active quarry. This October, I found plant impressions, insects, starfish and the odd small fish in this quarry during one short afternoon.

Another option is to go to a very large quarry located in a nearby hamlet called Ejerslev. It is rather hard to find, but when you come to Ejerslev, you have to find a way going west until you see a church. Just next to the church, there is a sign on a gravel road to Ejerslev Havn. Follow this for about 500m, pass a house on the left-hand side of the road and, after some trees, there is another gravel road on the left with a sign warning of falling rocks. Take that road, keep to the right and find a place to park when you get to an area where several gravel roads meet.

Now you are at the outskirts of the quarry. As this is very active, you have to look around to find a place where there is material to split. As a matter of fact, there is an area in front of the quarry where you can park and where waste material is dumped. Good fossils have been found in the waste piles here and this is where I found the leaf and the sharks’ teeth pictured in this article.

At last, we can move onto some photos of fossils. I have decided against showing some of the very impressive things kept in the museums – things that have been found over the last 100 years, which are incredible rare (and, of course, can be seen at the museums I have referred to). The fossils pictured here are from my collection found in the last five years.

Argentinoid fish (Fig. 5) are the most common fossils in the moler. Pieces of the vertebrae are very common, but complete specimens are more rare. With a bit of patience, you can find specimens from 3 to 10cm in length. These were found at Mors and at Fur.

Internal casts of bivalves (Fig. 6), a relative to the living Mytilus, can be found by are not very common. At Mors, several have been found in the last year or two. They did not live in the moler sea, but sailed to it attached to driftwood that, alas, sooner or later sunk, dragging the stowaways down with them.

The brittle star, Ophiura furiae (Fig. 7), are also found at Mors. These are not uncommon in a small section of the positive and the negative ash layer series. However, I have only found Ophiura at Mors, but they can apparently also be found at Fur.

The shark’s tooth shown on the right (Fig. 8) is sitting in a cementsten – in the soft moler, sharks’ teeth have dissolved, but you can of course make a cast using liquid rubber. This specimen is from Mors.

Insects are also regularly found (Fig. 9). The most common insect is a 10mm long shield bug, here shown on top of a cementsten from Mors. These are also common at Fur.

An Osmeroid fish (Fig. 10), unfortunately without its head, was found at a quarry in Mors (see the photograph at the beginning of this article showing collectors gathering around this find). The body is nearly 20cm long.

Decapods are rare fossils in the moler. This shrimp (Fig. 11) is called Morscrangon acutus and is the most common, but with probably less than 30 specimens found in all. Length 4.5cm. It was found at Fur.

A ‘raw’ fossil just brought home from Mors (Fig. 12) – the leaf of Macclintockia canei. When prepared, it should be some 15cm long if all of it is in this lump of soft moler. The tip of the leaf is normally missing. They are typical of moler, but certainly not common. The most common plant material that is found is fossilised/carbonised tree and impressions of leaves from a bamboo-like plant.

Finally, one minus point regarding moler: there is a very restricted and fragmented literature on the formation and it is mainly in Danish. So, whatever you find, go to the museum and get a name before going home. Otherwise, you might have to come back for another session of fossil hunting. However, you might want to do that anyway as it is easy to become obsessed by splitting laminated moler on a nice sunny day. My niece has compared people splitting moler to people who are hooked on that one last bet on just one more horse at the races – again and again forever.

Other articles in this series by Niels Laurids Viby
Fossils from Denmark (part 1)
Fossil from Denmark (part 2)
Fossils from Denmark (Part 3): Getting exercise by walking the beaches of Denmark for fossils
Fossils in Denmark (Part 4): Danish chalk