Photo: Green speleothems in the Aven du Mont Marcou (Hérault, France) © Stéphane Pire, Gaëtan Rochez (UNamur)

Speleothems, for instance stalactites and stalagmites, are commonly composed of calcite or aragonite (CaCO₃). This mineral compound comes directly from the rock in which the cave was formed and naturally has a white to brownish colour. However, speleothems can sometimes exhibit unique and unusual colours. From yellow to black, blue, red, green, and even purple, there is something for everyone! 

Such a diversity of colours reflects the many possible causes: mineralogical, chemical, biological, or even physical. A speleothem, like any natural formation, is never perfectly pure. Their deposition process, through the precipitation of calcium carbonate dissolved in water, is necessarily accompanied by the deposition of numerous impurities carried along with the water circulating underground. Even if these impurities are sometimes too low in concentration or simply uncoloured, they can still have a visible impact on the colour. 

OK, but what is the point?

The formation of speleothems is very often linked to impurities dissolved in groundwater. Therefore, studying coloured speleothems provides valuable information about potential contamination of surface water with heavy metals or other harmful organic compounds, which in some cases may be consumed by residents. It is therefore a simple and direct way to identify areas with potentially contaminated water and to determine whether this contamination poses an environmental or health risk.

This is the objective of Martin Vlieghe's thesis: to apply a range of cutting-edge analytical techniques to samples of these speleothems to determine these causes and propose an explanation for the origin of the colouring elements. 

Here are a few examples.

An initial project explored the green speleothems of the Aven du Marcou (see photo above). Located in the Hérault department of France, this chasm is well known in the area for its series of impressive shafts, the largest of which is over 100 meters deep. It also has a tiny chamber hidden at the top of a steep wall, which houses an impressive concentration of deep green speleothems. After all the effort of descending and climbing ropes to progress through this very vertical cave, what a wonderful reward to discover this true underground gem! Once the initial wonder has passed, it's time to get to work!  We observe, describe, interpret, and collect a few green fragments from the ground, while respecting the integrity of the site as much as possible. Back in Belgium, it's time to move on to the analyses.

The discovery is all the more surprising given that there are no nickel deposits in the vicinity of the cave! Further study of the composition of the nepouite reveals that they contain a high concentration of zinc, which is also very unusual and suggests that they are in fact quite different from those commonly mined in volcanic deposits. Finally, this mystery was solved by a thorough examination of the rock outcrops in the immediate vicinity of the cave. Just above the cave are siliceous deposits particularly rich in pyrite, an iron sulphide commonly found in this type of settingst. Analysis of these sulphides reveals high concentrations of nickel, which is also found in the natural water source closest to the cave. 

The result of this "investigation" and final explanation: nepouite was able to settle underground through the dissolution of various chemical elements contained in the pyrite of the overlying rocks, which were transported into the cave by surface water and were able to crystallize on site. 

The Malaval cave is very different from the Aven du Marcou. Located in Lozère (France), it extends largely along a high underground river that winds beneath the Cévennes massif. At the bend of a meander, one can find magnificent blue speleothems. 

As in the Aven du Marcou, the coloured speleothems are found only in two specific locations in the cave and nowhere else, suggesting that the origin of the chromophore elements is probably very localized.

Photos - Left: Blue stalagmite in Malaval Cave. Right: Cluster of blue aragonites in Malaval Cave © Gaëtan Rochez (UNamur)

Once again, a few fragments were collected, including a large bluish stalactite found broken on the cave floor. A series of microscopic observations and mineralogical and geochemical analyses were carried out. The first striking finding was that several blue fragments contained no minerals other than aragonite, suggesting that, unlike the green ones from Marcou, it was the aragonite itself that was coloured by the presence of metallic elements. After examining the analyses, three of these elements stood out: copper, commonly cited as the cause of blue colouring in aragonite, as well as zinc and lead. 

While copper appears to be the main cause of the blue colouration, zinc and lead also play a role here. 

Lead also has a marked colouring power, producing green to blue hues, but statistical analysis of coloured and uncoloured areas shows that these colours only appear in the absence of zinc, which seems to inhibit lead-induced colouring. This study clearly demonstrates that, even if a problem seems easy to explain at first glance, it can sometimes hide unexpected subtleties that need to be explored in greater depth in order to uncover all its secrets. 

The Cigalère Cave is one of a kind. Not only does it contain impressive quantities of gypsum, a calcium sulphate found in certain caves, but this gypsum also displays a wide variety of colours rarely seen in nature. Because of this rarity, the cave is particularly well protected, to the point that we were not allowed to collect any fragments from inside it. 

This study was therefore the ideal opportunity to test the Geology Department's new acquisition: a portable X-ray fluorescence spectrometer (pXRF), which allows rapid, in situ, and above all completely non-destructive analysis of coloured speleothems.

Photos - pXRF analysis of a blue stalactite core (left) and a yellow flowstone (right) in the Cigalère Cave © Stéphane Pire (UNamur)

Black is also found in the Chapelle de Donnea, but contrary to what one might think, no iron has been detected. Here, it is manganese in the form of oxides that is responsible for the colouration. This observation is interesting because it clearly demonstrates that black colouration in gypsum, two phenomena that appear similar at first glance, can have very different causes, hence the importance of being able to carry out analyses directly in the field. 

A little further downstream, blue dominates along the main gallery, and analyses have shown strong similarities with the blue speleothems of Malaval, with a marked influence of copper and potentially zinc. 

All this highlights that, despite certain limitations of the device, this type of non-destructive analysis method is a very valuable tool for studying rare, fragile, precious, or protected objects, of which the Cigalère cave is an excellent example! 

Martin Vlieghe's doctoral thesis on "The origin(s) of colored speleothems in caves," supervised by Professor Johan Yans and in collaboration with Gaëtan Rochez, began in February 2022. All three researchers are members of the Faculty of Sciences, Department of Geology at UNamur and the ILEE Research Institute. 

ILEE (Institute of Life, Earth and Environment) is directly involved in issues related to the study and preservation of the environment, to which this subject is directly linked. 

The various analyses were carried out with the support of UNamur's technological platforms:

• Physicochemical characterization (PC²)
• Lasers, optics, and spectroscopy (LOS)
• Electron microscopy
• Synthesis, Irradiation and Analysis of Materials (SIAM)

Some analyses were carried out in partnership with KUL, MRScNB and UMontpellier, and access to the caves was provided by the Association Mont Marcou, the Malaval Association and the Association de Recherche souterraine du Haut Lez.

This thesis was originally funded by the ILEE institute and institutional funds from UNamur, and by an Aspirant F.R.S. - FNRS grant (FC 50205) since October 2023.

It is also closely linked to the new research partnership supported by the RELIEF network (Réseau d’Échanges et de Liaisons entre Institutions d’Enseignement supérieur Francophones), the ILEE research institute at UNamur, and EDYTEM (Environnements, Dynamiques et Territoires de Montagne, Université Savoie Mont Blanc).  Mobility programs between these entities will strengthen a common research area: the study of the critical zone, the most superficial zone of the Earth, where rocks, water, air, and living organisms interact. The perspective is to develop other transdisciplinary research areas and potential teaching projects in the field of environmental sciences and sustainable development.

Studying geology means developing a solid foundation in physics, chemistry, and biology in order to understand the Earth, from its internal dynamics to surface processes and their interactions with our environment and human activities. 

Thanks to their interdisciplinary training, geologists are ideally positioned to perform a variety of roles that require a rigorous scientific approach to solving complex problems (research and development, project management, consulting, and education).

What are the advantages of studying at UNamur? 

• Practical training and numerous field activities
• Strong scientific foundations
• Immersion in geology from block 1
• The possibility of ERASMUS from block 3 onwards
• Close contact with teachers

Astronaut Raphaël Liégeois will be carrying some rather unusual passengers in his luggage: dried blob samples, some of which have been irradiated with X-rays at UNamur. What are the Namur scientists hoping to achieve? They want to observe how this organism responds to the space environment and is able to repair its DNA in microgravity, and compare these results with those obtained in a similar experiment carried out on Earth. "In our laboratory, we simulate the stresses that the blob could undergo in space in order to assess its ability to survive and repair itself," explains Anne-Catherine Heuskin, professor in the Department of Physics.

While awaiting the rocket launch scheduled for 2027, researchers at UNamur are already actively preparing for the mission. For several months, they have been conducting a series of tests to ensure the reliability of the experiment: reaction to temperature variations, power failures, transport to the launch site in Florida, assembly of the mini-spacecraft that will house the samples, etc. "Every detail counts: even the choice of bags that protect the samples from light can influence the results," emphasizes Boris Hespeels.

Once on the ISS, Raphaël Liégeois will rehydrate the samples, culture them in a cabin on the station, and finally place them in a freezer at -80°C. "This procedure, which seems simple, becomes complex in zero gravity. We also have to ensure the stability of our samples, regardless of the timing of the experiment," continues Boris Hespeels. Inside the ISS, Raphaël Liégeois will have to carry out various experiments selected by the Belgian Science Policy Office (BELSPO). "And the order in which they will be carried out has not yet been determined," the two Namur-based researchers explain.  

Post-mission analyses will identify cellular protection mechanisms under extreme conditions. These results could inspire the development of protective molecules for astronauts or patients undergoing radiotherapy. "Space remains a hostile environment. Understanding how living organisms adapt to it is essential for preparing future exploration," Boris Hespeels points out.

Finally, the BeBlob project also has an educational component: activities based on the blob will be offered in schools to raise awareness among young people about scientific research and space exploration. An ambitious project is also under consideration to enable students aged 8 to 18 to work directly on samples that took part in Raphaël Liégeois' mission aboard the ISS.

The University of Namur is establishing itself as a key player in the study of the blob. Researchers at the LARN (Laboratory for Nuclear Reaction Analysis) and the ILEE (Institute of Life, Earth and Environment) and NARILIS (Namur Research Institute for Life Sciences) institutes have been conducting research into radiation resistance and DNA repair for several years. The BeBlob project builds on experience gained during previous space missions and active collaboration with ESA and BELSPO. The BeBlob project is one of three Belgian scientific experiments selected from 29 projects to be carried out during Belgian astronaut Raphaël Liégeois' mission scheduled for 2027. This scientific expertise places UNamur at the heart of space biology and fundamental research on life in extreme environments. The project is part of UNIVERSEH, the ERASMUS+ alliance of European universities that aims to build a "European university" focused on the space sector, of which UNamur is a member. 

The "Credits & Projects" call for proposals resulted in 12 grants being awarded for ambitious new projects. These include two "equipment" grants, eight "research credits (CDR)" grants, and two "research projects (PDR)" grants, one of which is in collaboration with the ULB. The FRIA call for doctoral research support will fund eleven doctoral scholarships and the FRESH call will fund three. 

Two prestigious Scientific Impulse Mandates (MIS) were also obtained. This three-year funding supports young permanent researchers who wish to develop an original and innovative research program by acquiring scientific autonomy within their department.  

We would also like to highlight the two projects funded under the "WelCHANGE" call, a funding instrument for research projects with potential societal impact, led by a principal investigator in the humanities and social sciences.

Call for Equipment  

• Xavier De Bolle, Narilis Institute, Co-promoter in collaboration with UCLouvain
• Luca Fusaro, NISM Institute 

Call for Research Grants (CDR) 

• Marc Hennequart, NARILIS Institute
• Nicolas Gillet, NARILIS Institute
• Jean-Yves Matroule, NARILIS Institute
• Patricia Renard, NARILIS Institute
• Francesco Renzi, NARILIS Institute
• Stéphane Vincent, NISM Institute
• Laurence Meurant, NaLTT Institute
• Emma-Louise Silva, NaLTT Institute  

Call for Research Projects (PDR) 

• Jérémy Dodeigne, Transitions Institute, Co-supervisor in collaboration with ULB
• Luc Henrard, NISM Institute; Co-supervisor: Yoann Olivier, NISM Institute 

Fund for Training in Research in Industry and Agriculture (FRIA)

• Emma Bongiovanni - Supervisor: Catherine Michaux, NISM Institute
• Simon Chabot - Supervisor: Carine Michiels, Narilis Institute; Co-supervisor: Anne-Catherine Heuskin, Narilis Institute
• Lee Denis - Supervisor: Muriel Lepère, ILEE Institute
• Maé Desclez - Supervisor: Johan Yans, ILEE Institute; Co-supervisor: Hamed Pourkhorsandi (University of Toulouse)
• Pierre Lombard - Supervisor: Benoît Muylkens, Narilis Institute; Co-supervisor: Damien Coupeau, Narilis Institute
• Amandine Pecquet - Supervisor: Nicolas Gillet, Narilis Institute; Co-supervisor: Damien Coupeau, Narilis Institute
• Kilian Petit - Supervisor: Henri-François Renard, Narilis Institute; Co-supervisor: Xavier De Bolle, Narilis Institute
• Simon Rouxhet - Supervisor: Catherine Michaux, NISM Institute; Co-supervisor: Nicolas Gillet, Narilis Institute
• William Soulié - Supervisor: Yoann Olivier, NISM Institute
• Elisabeth Wanlin - Supervisor: Xavier De Bolle, Narilis Institute
• Laura Willam - Supervisor: Frédérik De Laender, ILEE Institute 

Fund for Research in the Humanities (FRESH) 

• Louis Droussin - Supervisor: Arthur Borriello, Transitions Institute; Co-supervisor: Vincent Jacquet, Transitions Institute
• Nicolas Larrea Avila - Supervisor: Guilhem Cassan, DeFIPP Institute
• Victor Sluyters – Supervisor: Wafa Hammedi, NADI Institute
• Amandine Leboutte - Co-supervisor: Erika Wauthia (UMons); Co-supervisor: Cédric Vanhoolandt, IRDENa Institute.

Scientific Impulse Mandate (MIS) 

• Charlotte Beaudart, Narilis Institute
• Eli Thoré ILEE Institute 

WelCHANGE Call  

• Nathalie Burnay Transitions Institute, in collaboration with UCLouvain
• Catherine Guirkinger, DeFIPP Institute

Congratulations to all! 

Photo: Excavation site at Albas, Massif des Corbières (France) © Gaëtan Rochez (UNamur)

Current predictions for biodiversity evolution in the face of climate change are based on models and scenarios derived from multidisciplinary studies. An article has just been published in the prestigious journal PNAS (Proceedings of the National Academy of Sciences), feeding into these scenarios. The researchers' original idea? To envisage an analogy between the biodiversity of the past and that of the future.

To understand, we need to go back 56 million years, to the transition between the Paleocene and the Eocene, a period characterized by intense global warming (named Paleocene-Eocene Thermal Maximum - or PETM). Paleoclimatologists consider this period to be a geological analogue of today's warming in terms of its amplitude (an increase of 5 to 8°C) and cause (a massive release of CO₂ into the atmosphere, similar to what we experience today).

At this time, global warming generated major disturbances on fauna. This change in climate, although 10 to 100 times slower than the one we experience today, coincided with the appearance of "modern" placental mammals (of which humans are a part), but also artiodactyls (ruminants, goats...), perissodactyls (horses, rhinoceroses...), bats, rodents and so on. Intense and rapid climatic disturbances generate major stresses on ecosystems: organisms try to adapt, some disappearing because they are unable to cope with these intense environmental changes, while others develop or evolve. This scenario was already well known...

But a few thousand years before PETM, another warming episode, named Pre-Onset Event (or POE), is recorded. It is less intense (+2°C) than the PETM, and more similar to current climate disturbances, leading researchers to investigate its impacts on faunas.

Photo: In search of fossils by fellow paleontologists from the University of Montpellier © ISEM

Field research has been carried out in the Massif des Corbières, southern France: the geological layers representative of this period are numerous and thick. Thanks to carbon isotope geochemistry, Namur researchers have been able to date these layers with great precision, making it possible to detail the evolution of fossils over time.

The fossils thus discovered have delivered their memory. And this calls into question previously established scenarios on two key aspects:

• Species evolved rapidly as early as the EOP, a climatic event similar to today's disturbances.
• While researchers thought that European faunas were composed of species endemic to Europe, they discovered that these archaic animals also rubbed shoulders with more modern species, such as marsupials or rodents, having probably migrated from North America during the EOP.

Photo: Mammal fossils discovered at Albas preserved in small glass tubes. These are the tiny teeth of a small "archaic" mammal called Paschatherium. Rodolphe Tabuce

So, during the EOP, species migrated from one continent to another... But how is this possible? It was thought that, at the time, the European continent was relatively isolated from the others by shallow seas. In reality, as a result of global warming, vast expanses of forest covered the high latitudes (present-day northern Greenland, Scandinavia and the Bering Strait in Siberia), serving as "natural land bridges" for forest fauna! Climatic disturbances therefore modified the flora, which in turn served as a passage between continents for "modern" faunas, also in the midst of upheaval.

The climatic disturbances of the POE, similar to those recorded today, therefore drastically influenced the faunas, notably by facilitating intercontinental migrations.

The impact of these decisive events during the EOP offers new avenues for reflection and study on the future of biodiversity in the context of current and future global warming.

"EDENs: Life during past super-warm climate events: Evolutionary Dynamics of Early EoceNe mammals from Southwestern France" is a multidisciplinary and international project in which Johan Yans, Jean-Yves Storme and Gaëtan Rochez (Department of Geology and ILEE Institute at UNamur) have been involved for the past 3 years. This research brings together the expertise of various partners:

• L'Institut des Sciences de l'Evolution de Montpellier (ISEM), Rodolphe Tabuce and Fabrice Lihoreau,
• Géosciences Montpellier, Flavia Girard and Gregory Ballas.

It is funded by the Agence Nationale de la Recherche (ANR-France). Its mission is to support and promote the development of fundamental and finalized research in all disciplines, and to strengthen the dialogue between science and society.

• Climate warming 56 million years ago: can biodiversity from the past help us anticipate the future? - The Conversation
• Climate warming: can biodiversity from the past help us? - RTBF

In terms of training, in addition to courses incorporating the SDOs, the University of Namur offers the University Certificate of Further Training in Sustainable Development. Aimed at members of organizations, administrations, companies, schools, etc. concerned or simply interested in the implications and challenges of sustainable development, it aims to offer information that is as thoughtful and diversified as possible, in order to help each participant better position, in his or her professional context, the issues linked to sustainable development that concern him or her more directly.

In terms of research, researchers work through 11 interdisciplinary research institutes. Johan Yans' team is active within the Institute ILEE - Institute of Life, Earth and Environment - and this research is a focus of activities devoted to Sustainable Development at UNamur.