Speaker
Prof.
Daniele Pinti
(GEOTOP - Université du Québec à Montréal)
Description
Stalagmites can provide very high-resolution (seasonal to annual) continental archives for paleoenvironmental reconstructions (Bar-Matthews et al, 1991, Bar-Matthews et al, 1997) due to their precise chronology and their ability to register climatic and environmental changes through proxy-tools such as stable isotopes \delta ^{13}C and \delta ^{18}O (McDermott, 2004) and trace elements (Fairchild et al, 2000, 2001). Fallen or broken speleothems can be also used as record of past earthquakes (seismothems) (Quinif, 1996). However, to create precise paleo-seismic catalogues, as well as paleoclimatic detailed records at the century timescale, new dating methods need to be developed. The ability of precisely dating speleothems by U-series decay chain (U/Th disequilibrium) has played an important role for the choice of speleothems as reliable proxies for paleo-environmental reconstructions for the last 500kyrs (Upper Pleistocene timescale). However, studies of younger speleothems are still poorly documented because the difficulties in using U/Th dating method at century timescale. Speleothems often contain low U-contents (ppb levels) and traces of detrital contaminants, which require complicated age corrections. Such corrections result in relatively high uncertainties on the final age calculation. A very limited number of studies were done using ^{210}Pb excess for dating young speleothems (Baskaran and Iliffe, 1993). Here we present the results of ^{210}Pb on two actively growing laminated stalagmites form Han-sur-Lesse karst complex, Belgium. The mean objective of this work is to demonstrate the ability to use ^{210}Pb as a dating tool for young stalagmites. The variations of the activities of ^{210}Pb along of growing axis show near ideal exponential fit indicate the possibility of using this method as a dating tool for such stalagmites and several age models were established. In order to validate the ^{210}Pb ages, results were compared with annual counting laminae ages. The results show a well agreement between the ages derived from ^{210}Pb and those from laminae counting for the last 100 yrs. Next step will be to validate the reconstruction of climatic signal obtained through stable isotopes (\delta ^{13}C and \delta ^{18}O) and compare the results with climate instrumental data available for the region.
Quinif, Y., 1996. Ann. Soc. Geol. Belg. 119, 1-13; Bar-Matthews et al, (1991). J. Geol. 99, 189-207; Bar-Matthews et al, (1997). Quat Res. 47, 155-168; Jaubert et al, (2016). Nature. 534, 111–114; McDermott, F, (2004). Quarter. Sci. Rev. 23, 901–918; Fairchild et al. (2000). Chem. Geol., 166, 255-269; Fairchild et al., (2001). J. Geol. Soc. London, 158 (5), 831–841; Baskaran and Iliffe (1993), Geophys. Res. Letters. 20, 603-606.
Primary author
Dr
Bassam Ghaleb
(Geotop, Université du Québec à Montréal)
Co-authors
Prof.
Daniele Pinti
(GEOTOP - Université du Québec à Montréal)
Dr
Mohammed Allan
(AGEs, Géologie, Université de Liège)
Prof.
Nathalie Fagel
(AGEs, Géologie, Université de Liège)
Dr
Sophie Verheyden
(AMGC, Vrije Universiteit Brussel)
