Mrs Silvia Bernasconi2, Pr Klaus Holger Knorr3, Mrs Carrie Thomas2, Dr Arnaud Huguet1, Dr Boris Jansen4, Dr Sylvie Derenne1, Dr Guido Wiesenberg2
1CNRS/Sorbonne Université/EPHE, Paris, France, 2University of Zurich, Zurich, Switzerland, 3University of Münster, Münster, Germany, 4University of Amsterdam, Amsterdam, Netherland
Biomarkers are commonly used to reconstruct paleoenvironments in terrestrial archives, including peat sequences. Various biomarkers were thus analyzed to trace environmental changes along a 3.5 meter core collected from the Beerbergmoor sequence (Thuringia, Germany), covering the last ca. 6000 years. Whereas inputs of various origins (roots, Sphagnum moss and aboveground biomass) are observed below 250 cm, predominantly Sphagnum-derived biomass is suspected between 250 cm and 100 cm depth from elemental analysis and further supported by alkane and fatty acid composition. Polycyclic aromatic hydrocarbons argue for more natural burning below 250 cm, most likely during the phase of neolithic settlements in that area, whereas above 100 cm, their structures suggest more intense burning probably during the middle age and since the industrial revolution. Reconstructed temperatures based on glycerol dialkyl glycerol tetraethers are in good agreement with other climate reconstructions over the covered period. For the first time, an inversed model was applied to assess quantitative shifts in vegetation composition, based on the quantification of biomarkers from locally collected recent plants and roots. It revealed variations in root abundance along the sequence, with a minimum between 100 and 250 cm depth where Calluna vulgaris and Sphagnum capellifolium showed the closest match to the peat material, and a maximum within the uppermost 100 cm. Although this inversed modeling exercise still requires more fine-tuning, the first attempts already showed the strengths of this attempt to better quantify the contribution of different biomass sources to the bulk organic matter than by just looking at different molecular proxies like average chain length, carbon preference index and others, individually. Inversed modeling thus appears as a promising tool to improve our paleoenvironmental understanding, not only in peat sequences, but also in other soil and sedimentary settings.
Biography:
Distinguished senior scientist (DRCE) CNRS since 2016, Head of the biogeochemistry group of METIS laboratory. My research area is organic geochemistry and I combine various techniques of analytical chemistry to decipher the chemical structure of “geomaterials” to understand their formation pathway and behaviour in the environment. These “geomaterials” belong to a large diversity of natural environments such as sedimentary rocks, soil, natural waters and extraterrestrial materials. I co-authored 218 peer-reviewed papers and supervised 30 PhD students.
Awards: 2009 CNRS Silver Medal, 2019 Geochemical Society Alfred Treibs Medal
