Geochemical characterization (REE, Nd and Pb isotopes) of atmospheric mineral dust deposited in two maritime peat bogs from the St. Lawrence North Shore (eastern Canada)

Abstract

Dust deposited on two ombrotrophic peat bogs (Baie and IDH bogs) of the St. Lawrence Gulf and Estuary north shore (Quebec) was geochemically characterized using rare earth element (REE) concentrations, Nd and Pb isotopes along with particle grain size. Both cores display similar ɛNd values, which suggests either a common source or sources with similar signatures in both regions. Combining Nd isotope data with REE patterns and particle size allowed for better insights into the source of deposited dust and the inference of past environmental and climatic conditions in both regions. REEs, ɛNd and grain‐size distribution suggest that, over the last 2000 years, the Baie bog received more local dust due to increased local storminess in response to greater regional hydroclimatic variability. The same phenomenon occurred in the IDH bog since 620 cal a BP, i.e. during the Little Ice Age, where hydroclimatic and paleoecological changes have been previously documented. While the dust reconstructions and regional climatic records agree relatively well, the discrepancies between paleodust records highlight the complex and variable structure of late Holocene changes in paleoclimate and more particularly past dust deposition in eastern Canada.

The Anthropocene: Comparing Its Meaning in Geology (Chronostratigraphy) with Conceptual Approaches Arising in Other Disciplines

“…The signals are widespread, but nonetheless regional. Peat bogs throughout Europe offer clear evidence of Roman atmospheric Pb contamination (e.g., Cloy et al, 2005;Kylander et al, 2005;Le Roux et al, 2004;Monna et al, 2004;Shotyk et al, 2005), but there is no evidence of this signal in peat bogs sampled in North America (Pratte et al, 2017a(Pratte et al, , 2017bShotyk et al, 2016) or southernmost South America (Sapkota, 2006). The Wagreich and Draganits (2018) proposal of a GSSP based upon these far-field, albeit regional, stratigraphic records might be accommodated within the recent tripartite formal subdivision of the Holocene (Walker et al, 2018(Walker et al, , 2019.…”

Nd isotopes as a tracer of dust trapped by peat bogs: A reminder of basics. Comment on: « Neodymium isotopes in peat reveal past local environmental disturbances » by

“…and a topographic assessment to exclude the possibility of local mineral inputs prior to embarking on a reconstruction of atmospheric sources of dust (e.g. De Vleeschouwer et al, 2007, Fialkewicz-Koziel, 2018Li et al, 2020;Longman et al, 2017;Pratte et al, 2016Pratte et al, , 2017aPratte et al, ,b, 2020. All other types of peatland records (i.e.…”