500 million year old mud and clay

In my last blog I started to write about Alum Shale and more specifically about the Alum Shale of southernmost Sweden, which is about 500 million years old. It is fascinating that geologists can read these old rocks and reconstruct when, where and how these sedimentary layers formed originally, how they were transformed into rocks and how many deep burial phases these rocks had experienced. But it is even more surprising that a Quaternary geologist (me) suddenly finds such old rocks so very interesting. But then geology is geology, and the only differences are time and the environment in which the sediments were deposited.

Geologists from Lund University and from the Geological Survey of Sweden have done a great amount of work to reconstruct the depositional environment of the Alum Shale and its underlying and overlying rocks. To make these reconstructions, they worked on outcrops, but also with a number of deep drill cores, which were analysed using different techniques. The drill cores helped estimating the thickness of the Alum Shale and showed the contacts between the underlying sandstone and the overlying shale and limestone.

The first drill cores, Andrarum-1 and Andrarum-2 were made in the years 1941-1942 and were later complemented by core Andrarum-3. Ahlberg and co-authors (2009) describe this latter drill core in detail and also provide a good description of what the Alum Shale looks like. During the years 2009-2010, several new boreholes were drilled by Shell: Lövestad A3-1, Oderup C4-1 and Hedeberga B2-1, plus Fågeltofta-1, Flagabro-1, Gislövshammar-1 and Gislövshammar-2. Some of these were examined as part of a MSc thesis by Eriksson (2012), are for example summarized in Calner & co-workers (2013) and in Schovsbo & co-workers (2015; DOI: 10.3997/2214-4609.201413170), among many other publications.

Figure 2 in Eriksson (2012) – Map of parts of the Province of Skåne in southernmost Sweden showing the location of boreholes drilled since 1941. The Series 2 refers to the sandstone underlying the Alum Shale and Series 3 is the actual Alum Shale.

But what exactly is the Alum Shale? It is a dark grey to black laminated mudstone and shale that contains strongly smelling carbonate lenses (a really smelly stinkstone – imagine rotten eggs, but much worse). These latter formed during early diagenesis, i.e. when the mud and clay started to turn into rocks. The mudstones and shales, which are up to 100 m thick in southern Sweden, are rich in organic matter, in pyrite (an iron sulfide), phosphate and in trace elements.

The mud and clay, which later turned into Alum Shale, were deposited in a shallow marine environment and under almost anoxic conditions, meaning that there was little oxygen available at the sea floor and that organic matter could therefore be preserved (i.e. it was not eaten up by for example bacteria). The mud and clay reaching the ocean floor (did rivers transport all the sediments to the sea shore?) were most likely weathering products from the surrounding mountain chains and maybe also ash particles from volcanoes, but could also have been at least partly derived from submarine volcanoes or hydrothermal vents.

What makes the Alum Shale so special is its high amount of organic matter, the frequent occurrence of iron sulfides and the many trace elements, such as vanadium and uranium. More about these another time.

Here are some references in case you would like to read more:

Ahlberg, P., Axheimer, N., Babcock, L.E., Eriksson, M.E., Schmitz, B. & Terfelt F. (2009): Cambrian high-resolution biostratigraphy and carbon isotope chemostratigraphy in Scania, Sweden: first record of the SPICE and DICE excursions in Scandinavia. Lethaia, Vol. 42, pp. 2–16.

Calner, M., Ahlberg, P., Lehnert, O. & Erlström, M. (eds.) (2013): The Lower Palaeozoic of southern Sweden and the Oslo Region, Norway. Field Guide for the 3rd Annual Meeting of the IGCP project 591. Sveriges geologiska undersökning, Rapporter och meddelanden 133, 57–85.

Eriksson M. (2012): Stratigraphy, facies and depositional history of the Colonus Shale Trough, Skåne, southern Sweden. Dissertations in Geology at Lund University, No. 310, 37 pp.

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Becoming a Nimby

Three years have gone by since my last blog entry. A lot has happened during the past three years and I just felt far too busy to commit to writing a blog.

But today I decided to start writing again. Not about my travels, because I do not travel very much these days. Not about human evolution, because we don’t organize excursions to beautiful Les Eyzies anymore. Not about the Asian monsoon, because this research project is almost finished. Rather I plan to write about what it means to be nimby (= not in my backyard) and how this changed the way I look at the world.

Last year we received a letter from Bergsstaten, the Mining Inspectorate of Sweden, telling us that a company called Scandivanadium has acquired exploration permits for among others the land we own and where our summer house is in beautiful Österlen in Southeasten Sweden. The company had obtained exploration permits for an area of 21 792,92 ha in Southeastern Sweden, a region which is rich in culture and heavy on agriculture and in addition an attractive tourist destination.

Scandivanadium wants to explore the possibilities to mine Vanadium, a metal which is present in high concentrations in the Alum Shale, and which has gained importance during the past years as a component in redox-flow batteries. Right after the letter from Bergsstaten had arrived, my new Nimby career started. Not because I was afraid that our land could be turned into a mine – if that would happen, then I would just move elsewhere – but because I knew how geochemically complicated Alum Shale is, especially when exposed to weathering. But let’s not jump ahead and rather start with the basics and gradually move on from one topic to the next.

So what is Alum Shale? It is a black organic-rich shale that some 500 million years ago (Middle Cambrium to the lower Ordovicium) was deposited as clay in a large ocean basin. It is known for its high content of various metals and minerals (see for example Schovsbo 2003 or Erlström et al. 2004). The Alum Shale formation has historically been divided into three parts: the lowest is called Paradoxides Series, the middle part is termed Olenid Series and the upper part is termed Dictyonema Shale. These names stem from the fossils found in the shale.

The Swedish Dictyonema Shale has been known for a very long time for its exceptionally high Vanadium content. And it is this part of the Alum Shale, the Dictyonema Shale, which has now attracted the attention of Scandivanadium.


Schovsbo, N. H. 2003. The geochemistry of lower Paleozoic sediments deposited on the margins of Baltica. Bulletin of the Geological Society of Denmark. Vol. 50, p. 11-27.

Erlström, M. et al. 2004. Beskrivning till berggrundskartorna 2D Tomelilla NV, NO, SV, SO; 2E Simrishamn NV, SV; 1D Ystad NV, NO; 1E Örnahusen NV. Sveriges Geologiska Undersökning Af 212-214.

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SGU in focus

The Geological Survey of Sweden (SGU) has made media headlines during the past days. This government “expert agency for issues relating to bedrock, soil and groundwater in Sweden” recently changed is director and with the change in directors, there always come other big changes too.

The latest incident involves SGU’s library, which contains books and geological maps dating several hundred years back in time. Much of this work is – from a geological perspective – invaluable, because it only exists in one copy or represents data sets and maps from regions that are no longer accessible. SGU’s new director, who is not a geologist by training, now decided, based on an evaluation by consultancy firm Ernst & Young to close down the library, to move a small part of it to Uppsala University, and to just get rid of the rest. It is completely unbelievable to me how someone can at all consider such a thing! How can one honestly deprive Sweden’s geological community of all these works that have been assembled over so many years? How can one get rid of a treasure trove that is so rich and so important not only for Sweden’s geology and Swedish geologists, without carefully evaluating its importance? How can a consultancy firm decide what is valuable in terms of geology and what is not? And how could the director of SGU specify that all this should be done behind closed doors in order to not attract negative attention in the media?

Luckily SGU and its new director got exactly what they did not want. First an open letter signed by several Swedish geologists (me included), then SGU came in focus in Kulturnyheterna on December 4th, both during the 18:13 and 21:18 news and online; in the newspaper Svenska Dagbladet; and today in Dagens Nyheter.

Let’s hope that all this (unwanted) media attention puts a focus on what is going on at the Geological Survey of Sweden, and let’s hope that the elimination of this valuable library will stop. That SGU is also discussing its research program (the only funding available to many geologists in Sweden today), that it has stopped supporting the popular science journal Geologiskt Forum, and the new planned book on Sweden’s geology are just several more indications that SGU has entered a new era. And this new era really does not look bright for Sweden’s geology and not for Sweden’s geologists!

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Human adaptation to climate change in prehistoric NE Thailand?

This pretty challenging line, however without the question mark, is the title of a new manuscript, which we submitted yesterday. For this manuscript we pulled together all the paleoclimate evidences we have for Northeast Thailand based on our sedimentary records from Lakes Kumphawapi and Pha Kho, teamed up with the famous archaeologist Charles Higham from New Zealand, and came up with the hypothesis that Late Iron Age populations actually adapted to long-lasting weaker summer monsoon rains and did not just abandon their settlements. But let’s take it from the start!

By analysing a multitude of different proxies in the sediments of Kumphawapi and in the peat of Pa Kho we are now able to reconstruct the climate story for northeastern Thailand. This reconstruction shows that the summer monsoon was considerably stronger some 7000-8000 years ago. Our idea is that much stronger monsoon rains led to an increase in biomass, which in turn caused the shallower parts of Lake Kumphawapi to gradually overgrow. Subsequently drier climate conditions led to the formation first of a wetland and then of a peatland, which experienced multiple wetter and drier climate intervals. These climatic conditions – between 6500 and 2600 years ago – coincided with the immigration of Neolithic farmers (c. 3700 years ago) and the subsequent Bronze Age settlements (c. 3000-2600 years ago). This means that both Neolithic and Bronze Age people very likely lived in NE Thailand when climatic conditions were considerably drier and summer monsoon rains less intense.

Moisture history reconstructed for Northeast Thailand for the past 8000 years

Moisture history reconstructed for Northeast Thailand for the past 8000 years

With the start of the Iron Age (2600-2400 years ago) climatic conditions however changed and summer monsoon rains became stronger again, allowing Iron Age people to live a good live. These early Iron Age settlers decorated the graves of the deceased with surpluses of rice and nice exotic jewellery. Some 1600 years ago climatic conditions changed again, summer monsoon rains became weaker and also remained weak for the next 300-400 years. However and despite the obvious drought and aridity that swept over the country, later Iron Age populations increased, agriculture expanded, forests were cleared, iron and salt were mined on a large scale, and warfare increased. Mosts were constructed and also houses and a marked social stratification becomes visible in the mortuary goods. Instead of succumbing to drought, it seems that these late Iron Age populations adapted through distinct social changes to the change in climatic conditions. The settlements, which were constructed on mounds and surrounded by multiple moats (or channels), were later on merged into smaller city states. Even today many of these circular features can be seen in the landscape, and some still contain villages surrounded by moats to retain water to be used during the dry season. So – not abandonment, no overuse of available resources, and no going under? But – continuation, adaptation, and planning despite marked climatic changes?

Moated village in the Mun River Valley of Northeast Thailand

Moated village in the Mun River Valley of Northeast Thailand

It will be interesting to read what our reviewers will say! In a seminar today at the Earth Observatory of Singapore I tested this new hypothesis of adaptation versus migration/abandonment, and I am guessing that I convinced most of the audience!

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Student exchange opportunities! Grab it!

Why not spend some time in tropical Singapore, where the sun is (almost) always shining and temperatures never fall below 25 degrees C, and combine this with studying geosciences?

Thanks to an agreement between the science faculties at Stockholm University and Nanyang Technical University we can now offer a tailored exchange program for undergraduate students with the recently started Asian School of the Environment. The School’s programme in Environmental Earth System Science allows students to specialize in geosciences, ecology, and society and the earth system. Read more about the study program here and about the Geoscience Program at the Asian School of the Environment.

Field courses to Bali and to other areas in Southeast Asia form an integral part of the study programme.

Since the different courses at the Asian School of the Environment run in parallel over a whole semester, you would be required to spend a full semester in Singapore (fall semester: mid-August to mid-November; spring semester: mid-January to mid-May). Given that the academic year basically overlaps with that at Stockholm University, an exchange should be of no problem! For more information: NTU’s academic calendar can be found here.

The agreement between Stockholm University and Nanyang Technical University means taht you are not required to pay tuition fees and you will get full credits for your completed courses. What more can you wish for?

Maybe I should add that there is a wide range of sport facilities on campus? That there is a huge swimming pool with nice, warm water? That food on campus is cheap and good? That Singapore is a hub for reaching many destinations in Southeast Asia?

If you are a geoscience/geology student at Stockholm University and interested in taking exchange courses or doing a project work at the Asian School of the Environment, contact me by email (Barbara.wohlfarth@geo.su.se) or pass by my office in January when I am back in Stockholm after having spent three wonderful months here in Singapore.

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A view from far away

When I am abroad (and of course also when I am back home) I try to keep updated on what is going on by reading a variety of online news in the languages I know and by browsing through my FB page. The view I get when being abroad is that of a huge distance between me and what is going on in Europe, while when I am in Europe I feel that I am in the middle of what is happening and can easily get carried away by newspaper headlines and the general mood.

I am abroad now, far away from Europe and am living (for a few months) in a small country (Singapore) where people of many different cultures, ethnicity, languages, religions, background, and preference of food are living together in harmony. People dress the way they want, eat the food they want to eat, and pray where and when they want to pray. I could walk around in shorts, in a hijab or in a business dress and no one would look strange at me; I can eat Chinese or Indian food for breakfast, halal food for lunch and a burger for dinner; and I can go to a temple in the morning or pray five times a day and no one would think that this is strange.

The obvious success of Singapore with its just over 5.5 million inhabitants actually builds upon this racial, ethnic, cultural and religious harmony, which is praised as something really special and very important. From this view point, the various discussions and events in Europe (as perceived from my newspaper readings) come across as totally strange. Of course I am still very shocked by what has happened in Paris, but I am also always deeply shocked whenever I read about what is going on in Nigeria or in the Middle East, or elsewhere. But I am even more shocked by the negative opinions and the hate that are circulating in social media and by the way newspapers and politicians contribute to stirring up these feelings.

Let me however make one thing clear so that I am not misunderstood: I detest all kinds of violence, I think wars and atrocities committed between people are the most terrible things I can think of. I think wars are mainly being fought because they are big business (so much money can be made from producing the never ending amounts of weapons). I also think that religion and politics must be separated and that religion is each person’s own private matter. And, I think that violence just leads to more violence and that hate leads to more hate. What seems to be going on in Europe right now certainly does not give me a good feeling.

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It is actually a great feeling …

…. when your PhD student manages to get a paper accepted in Nature. It never happened to me before, but today was the day! Francesco, who had worked so hard on this paper and on the replies to the various reviewer comments, can see it printed in Nature Communications today. We paid pretty much to make the paper Open Access, so just go ahead and download as much and as often as you like!

The short scientific abstract reads “Sources and timing of freshwater forcing relative to hydroclimate shifts recorded in Greenland ice cores at the onset of Younger Dryas, ~12,800 years ago, remain speculative. Here we show that progressive Fennoscandian Ice Sheet (FIS) melting 13,100–12,880 years ago generates a hydroclimate dipole with drier–colder conditions in Northern Europe and wetter–warmer conditions in Greenland. FIS melting culminates 12,880 years ago synchronously with the start of Greenland Stadial 1 and a large-scale hydroclimate transition lasting ~180 years. Transient climate model simulations forced with FIS freshwater reproduce the initial hydroclimate dipole through sea-ice feedbacks in the Nordic Seas. The transition is attributed to the export of excess sea ice to the subpolar North Atlantic and a subsequent southward shift of the westerly winds. We suggest that North Atlantic hydroclimate sensitivity to FIS freshwater can explain the pace and sign of shifts recorded in Greenland at the climate transition into the Younger Dryas“.

A more digestable title and summary of the paper follow below:

Melting Scandinavian ice provides missing link in Europe’s final Ice Age story

Molecular-based moisture indicators, remains of midges and climate simulations have provided climate scientists with the final piece to one of the most enduring puzzles of the last Ice Age.

For years, researchers have struggled to reconcile climate models of the Earth, 13,000 years ago, with the prevailing theory that a catastrophic freshwater flood from the melting North American ice sheets plunged the planet into a sudden and final cold snap, just before entering the present warm interglacial.

Now, an international team of scientists, led by Swedish researchers from Stockholm University and in partnership with UK researchers from the Natural History Museum (NHM) London, and Plymouth University, has found evidence in the sediments of an ancient Swedish lake that it was the melting of the Scandinavian ice sheet that provides the missing link to what occurred at the end of the last Ice Age. The study, published in Nature Communications, today, examined moisture and temperature records for the region and compared these with climate model simulations.

Francesco Muschitiello, a PhD researcher at Stockholm University and lead author of the study, said: “Moisture-sensitive molecules extracted from the lake’s sediments show that climate conditions in Northern Europe became much drier around 13,000 years ago.”

Steve Brooks, Researcher at the NHM, added: “The remains of midges, contained in the lake sediments, reveal a great deal about the past climate. The assemblage of species, when compared with modern records, enable us to track how, after an initial warming of up to 4° Centigrade at the end of the last Ice Age, summer temperatures plummeted by 5°C over the next 400 years.”

Dr Nicola Whitehouse, Associate Professor in Physical Geography at Plymouth University, explained: “The onset of much drier, cooler summer temperatures, was probably a consequence of drier air masses driven by more persistent summer sea-ice in the Nordic Seas.”

According to Francesco Muschitiello the observed colder and drier climate conditions were likely driven by increasingly stronger melting of the Scandinavian ice sheet in response to warming at the end of the last Ice Age; this led to an expansion of summer sea ice and to changes in sea-ice distribution in the eastern region of the North Atlantic, causing abrupt climate change. Francesco Muschitiello added: “The melting of the Scandinavian ice sheet is the missing link to understanding current inconsistencies between climate models and reconstructions, and our understanding of the response of the North Atlantic system to climate change.”

Dr Francesco Pausata, postdoctoral researcher at Stockholm University, explained: “When forcing climate models with freshwater from the Scandinavian Ice Sheet, the associated climate shifts are consistent with our climate reconstructions.”

The project leader, Professor Barbara Wohlfarth from Stockholm University, concluded: “The Scandinavian ice sheet definitely played a much more significant role in the onset of this final cold period than previously thought. Our teamwork highlights the importance of paleoclimate studies, not least in respect to the ongoing global warming debate.”

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