The late Quaternary environmental evolution of marine Arctic Canada: Barrow Strait to Lancaster Sound

A marine sediment core from the east-central Canadian Arctic Archipelago (Core 86027-154; 74° 22.01′N 89° 51.26′W; 329 m water depth), studied by a multiproxy approach [lithostratigraphy, biogeochemistry, micropalaeontology (dinoflagellate cysts, other non-pollen palynomorphs, benthic and planktonic foraminifera, ostracods)], and encompassing 14 AMS 14C dates, provides valuable insights into regional deglacial to Holocene palaeoenvironments. Six palaeoenvironmental zones are recognized, based on prominent changes in the litho- and biostratigraphy. The waterlain diamicton of Zone I records immediate deglaciation, being derived from lift-off and calving of previously grounded glacial ice. Though deglacial timing is complicated by the sparsity of dating materials and the Portlandia Effect, age-depth model extrapolation places deglaciation at 11.54 cal ka BP. Zone II (11.5-11.0 cal ka BP) represents a distinct progression from initially ice-proximal to increasingly ice-distal conditions, interrupted by an interval of pervasive sea-ice (11.4-11.2 cal ka BP). Noteworthy biological activity commences in Zone III (11.0-9.7 cal ka BP) with a prominent signal of planktonic foraminifera (Neogloboquadrina pachyderma). This likely signifies penetration of deeper, Atlantic-derived water through the central Canadian Arctic Archipelago upon deglaciation, facilitated by the greater, glacioisostatically-induced water depths (+80 m), and implies separation of Laurentide and Innuitian ice sheets by ∼11.0 cal ka BP. Zone IV (9.7-7.2 cal ka BP) records ameliorated, biologically favourable conditions with reduced seasonal sea-ice accompanied by high microfossil species diversity and the presence of subpolar taxa. Zone V (7.2-6.5 cal ka BP) signals the exclusion of Atlantic-derived water, concomitant with increasing sea-ice, simultaneously representing the termination of the dynamic deglacial to early Holocene environments (zones I-IV). Conditions similar to modern typified by uniform sediment characteristics, present-day microfossil assemblage structures, and sparse benthic foraminifera were established by 5.6 cal ka BP (Zone VI).