Deciphering human-climate interactions in an ombrotrophic peat record: REE, Nd and Pb isotope signatures of dust supplies over the last 2500 years (Misten bog, Belgium)

Nathalie Fagel (1) , Mohammed Allan (1) , Gaël Le Roux (2) , Nadine Mattielli (3) , Natalia Piotrowska (4) , Jaroslaw Sikorski (4)

1 Université de Liège
2 LEFE - Laboratoire Ecologie Fonctionnelle et Environnement
3 ULB - Université libre de Bruxelles
4 Silesian University of Technology

A high-resolution peat record from Eastern Belgium reveals the chronology of dust deposition for the last 2500 years. REE and lithogenic elements in addition to Nd and Pb isotopes were measured in a 173 cm age-dated peat profile and provide a continuous chronology of dust source and intensity. Calculated dust flux show pronounced increases c. 300 BC, 600 AD,1000 AD, 1200 AD and from 1700 AD, corresponding to local and regional human activities combined with climate change. The Industrial Revolution samples (1700-1950 AD) are characterised by a significant enrichment in Sc-normalised REE abundance (sum REE/Sc > 25) due to intensive coal combustion. For the pre-Industrial Revolution samples, the Sc-normalised REE abundance (10 < Sum REE/Sc < 25) and the eNd variability (-13 to -9) are interpreted by a mixing between dust particles from local soils and long-range transport of desert particles. Three periods characterised by dominant-distal sources (c. 320 AD, 1000 AD and 1700 AD) are consistent with local wetter-than-average intervals as indicated by a lower degree of peat humification. Local erosion prevails during the drier (higher humification) intervals (100 AD,600 AD). On a global scale, more distal supplies are driven during colder periods, in particular during the Oort and Maunder minima, suggesting a potential link between dust deposition and global climate. Combining REE abundance, fractionation between Light REE and Heavy REE and Nd isotope data in ombrotrophic peat allows one to distinguish between dust flux changes related to human and climate forcings.

Mots clés: Dust; Europe; Holocene; Aerosol; REE; Nd isotopes

Domaines: Géologie appliquée; Géochimie; Milieux et Changements globaux

Nathalie Fagel, Mohammed Allan, Gaël Le Roux, Nadine Mattielli, Natalia Piotrowska, et al.. Deciphering human-climate interactions in an ombrotrophic peat record: REE, Nd and Pb isotope signatures of dust supplies over the last 2500 years (Misten bog, Belgium). Geochimica et Cosmochimica Acta, 2014, vol. 135, pp. 288-306. ⟨10.1016/j.gca.2014.03.014⟩. ⟨hal-00988093⟩