Deglacial to Holocene changes in sediment characteristics and provenance in core GeoB22336-4 from Lancaster Sound Trough Mouth: Implications for environmental conditions in northwestern Baffin Bay

The Lancaster Sound is currently one of the pathways for Arctic water and ice entering Baffin Bay. However, this gateway was blocked by the coalescing Laurentide and Innuitian Ice Sheets during the Last Glacial Maximum and only opened during the early Holocene after the various ice sheets had retreated (Dyke et al., 2002; Dalton et al., 2020). Core GeoB22336-4 is a well radiocarbon-dated sediment record from the Lancaster Sound Trough Mouth. Sedimentological and geochemical (elemental and mineralogical) properties of this core revealed four major units: (i) the deglacial unit (~14.5 – 9.7 ka BP) with a dense, foraminifera-free, gravel-rich diamict (>14.0 ka BP) that captures proximal ice-margin conditions, probably deposited under an extended thick ice-shelf environment, overlain by rapidly deposited gravel-bearing sandy-silty mud with intercalated turbidite layers reflecting strong input of ice-rafted material and mass wasting, likely resulting from the fast landward retreat of bordering ice sheets in response to regional warming; (ii) the early Holocene unit (~9.7 – 8 ka BP) characterized by a drop in sedimentation rate and the absence of ice-rafted material and reduction in detrital carbonates, suggesting a switch from tide-water to predominately land-terminating glaciers during glacial retreat; (iii) the unit deposited contemporaneously with the regional Holocene Optimum (~8 – 5.9 ka BP; Ledu et al., 2010; Jennings et al., 2011; St-Onge & St-Onge 2014) consists of rapidly deposited rather fine-grained sediments (up to 52 cm ka^-1) possibly related to enhanced meltwater- and/or sea-ice-driven sediment input; and (iv) the neoglacial unit (<5.9 ka BP) with reduced sedimentation rates, a sediment provenance switch from calcite-dominated to dolomite-dominated detrital carbonates, and an increased organic matter flux to the seafloor, which led to a four-fold increase in bioturbation. This diverse sedimentary record reflects the complex ice-ocean-atmosphere interactions controlling the sedimentary dynamics and sediment provenance in northwestern Baffin Bay from the last deglaciation through the Holocene. It sheds light on the complex interaction between sediments delivered by local meltwater sources, mass wasting, iceberg and sea ice-rafting, the opening of the Arctic gateways through Lancaster Sound and Nares Strait, and the influence of warm Atlantic Water (AW). In addition, the Arctic Oscillation (AO) possibly governs surface waters and primary production in northern Baffin Bay including the development and extension of the North Water Polynya (NOW).