Postglacial palaeoenvironmental reconstruction of the Fury and Hecla Strait region (Nunavut) inferred from microfossils and geochemical proxies

An analysis of sediment records from two lakes located along the southeastern shore of the Fury and Hecla Strait (Nunavut, Canada) allowed us to reconstruct the regional environmental history since deglaciation. Multiproxy profiles, namely particle-size distribution, elemental geochemistry (based on X-ray fluorescence) and diatom assemblages, revealed a regional deglaciation and marine inundation around 8200 cal a bp. This suggests that glacial retreat in this region likely occurred several hundred years earlier than previously extrapolated. At that time, the connection between the Atlantic and Pacific Ocean currents must have been established and glacial isostatic adjustment gradually isolated the lacustrine basins from marine influence. Diatom assemblages revealed an abrupt marine-brackish-freshwater transition (ca. 6670-6130 cal a bp) through a shift in dominance from initial polyhalobian (e.g. Tabularia fasciculata, Navicula directa), intermediate mesohalobian (e.g. Cyclostephanos dubius, Thalassiosira baltica) to oligohalobian (fragilarioid Staurosirella pinnata, Staurosira venter, Pseudostaurosira pseudoconstruens, P. brevistriata) taxa. Multivariate analyses (redundancy analysis and multivariate regression tree) conducted on the biological and lithogeochemical data also suggest that climatic conditions may have remained relatively warm throughout the interval similar to 6000-3900 cal a bp, before significantly cooling over the past few millennia, as inferred from a decrease in organic matter accumulation and shifts in diatom communities.