Research unit : GEOL

Isotope Geology and Evolution of the Paleoenvironments

Current research projects

Laboratories and analytical facilties

Geoarcheology 

Recent thesis topics

Meetings

Research statement

The geology department focuses its activities on Earth and environmental sciences, which means a broad scope of interests. The experimental approach relies on the use of 'isotope geology'; this is why the department hosts several mass spectrometers for the precise determination of key isotopic systems. The isotopes are powerful geological tools, with a broad range of application, often resulting in stimulating inter-university projects and international collaborations.

What can isotopes bring about to the knowledge of geologic and environmental processes?

Fractionation processes affecting the light isotopes (H, C, N, O, S) are important in many fields of Earth and environmental sciences. Recently, the fractionation of heavier isotopes (Fe, Cr, Cu etc.) also started to be the topic of numerous studies.  Stable isotopes allow identifying and quantifying past climatic changes, or physico-chemical modification affecting low and high temperature mineralogical systems. Their signatures can also be used as a tracer of various environmental processes, in hydrogeology for example or to characterize organic matter in sediments. These techniques also have applications in other fields from oceanography to biology all the way to medical sciences.

Geochronology is based on a radioactive-radiogenic isotope pairs, in the present case ⁴⁰K and ⁴⁰Ar (K-Ar and Ar-Ar methods). This versatile method allows the absolute dating of ancient rocks or meteorites to the eruption of the volcano Vesuvius in roman times (-79 BC). Geochronology is of paramount importance in many geological questions such as the calibration of the stratigraphic time scale to the timing of various geological events.

The research unit “isotope geology and evolution of the paleoenvironments” studies selected events throughout Earth history.  There is a strong focus on paleoclimatic research in the last few million years, essentially by probing the continental record.  Another major research direction documents the origins and consequences of major biological and climatic changes through geological time.

The isotopic compositions (¹⁸O/¹⁶O and ¹³C/¹²C) of calcite in speleothems (stalagmites) from various locations worldwide are used to reconstruct climates over the last 10.000 years. These reconstructions are supported by precise dating using the U-Th or ¹⁴C methods. At the same time, the caves where they grow are closely monitored to understand the environmental parameters driving the precipitation of calcite.

The causes and mechanisms of biological mass extinctions are investigated in details, in particular how the impact of a ~ 10 km asteroid in Yucatan triggered the end of the dinosaurs along with 60% of the Earth fauna and flora, 65 million years ago at the Cretaceous-Tertiary (KT) boundary.  There is also a major emphasis on the study of craters and ejecta deposits.  The group uses platinum group elements to infer the type and origin of the projectile, in other words, the kind of meteorite, responsible for the formation of the impact structure.  This work contributes to documenting the astronomical sources of Earth crossing objects, either in the asteroid belt or as short or long range comets. Dating of major magmatic or hydrothermal events by using the Ar-Ar geochronometry is another research topic: this technique was used for example to time the metallogenesis of the Brabant massif in Belgium. 

Besides these major research fields, attention is also devoted to Sr-isotope geochemistry and Rb-Sr geochronology, geoarcheology and biogeochemistry. In addition, there is a growing interest in biomineralisation, exobiology and the origin of life on Earth and on other planetary bodies.