How can we study the environmental variations that have marked the history of the earth? When sediment samples are taken from geological strata, how can we know if their indications concern a local development (like the growth of a reef) or larger scale events (like a rise in the level of the oceans)? From such questions grew a new project co-founded by UNESCO and directed through the ULg. This leadership is a consequence of the work done by the sedimentary petrology laboratory (1).

Erosion. Global climate change. Continental drift. These are some of the factors that modify the landform of the earth. There’s nothing to worry about; we are talking about change in geological time. The traces of the history of landforms and landscapes that remain in geological strata have been there for millions if not billions of years. Each stratum’s rocks have been affected by the depth of the sea, by the general climate, and by communities of organic life and landscapes that existed at a certain place when particular strata were deposited.

Various techniques allow scientists to analyze geological strata in order to reconstruct the development of marine environments across geological periods, and thus to increase our knowledge of the history of life and the natural variability of climates. “We are studying “global change” on a scale of millions of years,” says Professor Frédéric Boulvain, of the sedimentary petrology laboratory at the University of Liège.

The study of layers of sedimentary rocks from different eras at a single site, or of strata from the same geological period collected at many places around the world permits scientists to retrace the development over time of the environments that have existed at different places on earth. Sometimes one is surprised to discover that our region, which once was located south of the equator, was for a long time covered by tropical waters, beneath which reefs like the Great Barrier Reef near Australia came into being (about 390 million years ago). Plate tectonic movement gradually moved the land mass that would later be Western Europe (and which would not emerge from beneath the ocean for millions of years to come) into the northern hemisphere.

(1) DA SILVA A.-C., POTMA K., WEISSENBERGER J.A.W., WHALEN M.T., HUMBLET M., MABILLE C., BOULVAIN F., Magnetic susceptibility evolution and sedimentary environments on carbonate platform sediments and atolls, comparison of Frasnian from Belgium and Alberta, Canada, Sedimentary Geology, 2009, 214, 3-18.