Abstract
Dust deposition in north-eastern Canada was estimated from the geochemical signature of a boreal peat bog from the James Bay lowlands. The rare earth elements and other lithogenic elements, as well as Nd isotopes were measured by Q-ICP-MS, ICP-OES and MC-ICP-MS, respectively along a 4.20m peat core covering the last 7000years. A principal component analysis performed on the geochemical dataset shows that REEs display the same chemical behavior as other lithogenic elements such as Al and Ti, which suggests that they are immobile in the peat column and can be used as tracers of dust deposition. After 4000calyrBP, peaks in dust deposition associated with greater variability in testate amoebae assemblages and plant macrofossil composition as well as a change in ɛNd values are observed. Between 7000 and 4100calyrBP, the ɛNd values varied from −36 to −29, while they gradually increased from 4100calyrBP until 1500calyrBP, suggesting proportionally less dust from local source(s) is deposited in favor of more regional source(s). From 1500calyrBP, ɛNd values remained relatively stable around −15 and −12. Most of the dust peaks correspond to documented cold and dry periods likely linked to intrusion of arctic air masses. A migration of the polar front might explain the more frequent intrusion of Arctic air masses in the region and the greater variability in the LG2 record over the last 4000years.
Published Version
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