Deglacial and Holocene sediment dynamics and provenances off Lancaster Sound: Implications for paleoenvironmental conditions in northern Baffin Bay

Abstract

Since the last deglaciation, Baffin Bay between Greenland and Canada developed from an isolated marginal sea to a major Arctic-Atlantic throughflow closely linked to the North Atlantic circulation. While the initial steps of gateway openings through Lancaster Sound and Nares Strait to northern Baffin Bay are reasonably well documented, far less is known about related regional deglacial-to-Holocene changes in sediment sources and depositional processes due to a lack of continuous and well-dated paleoenvironmental records from northern Baffin Bay. Sedimentological, mineralogical, and radiogenic isotope data of the well-dated sediment core GeoB22336-4 from the mouth of Lancaster Sound provide new insights on the impacts of ice-sheet retreat and opening of the gateways to the Arctic Ocean on the depositional setting. Basal subglacial till deposits point to a grounded ice stream at the mouth of Lancaster Sound before ∼14.5 ka BP. Subsequent glaciomarine sedimentation is characterized by the input of ice-rafted detritus (IRD), bioturbation traces, and foraminifera shells. Decreasing sediment supply and input of IRD through time reflects a period of ice-sheet recession to predominantly land-terminating positions during the Early Holocene. Changes in radiogenic isotope signatures reveal the openings of Lancaster Sound between ∼10.4 and 9.9 ka BP and of Nares Strait between 8.5 and 8.2 ka BP, in alignment with earlier studies. The rapid mid-Holocene (up to ∼5.8 ka BP) deposition of fine-grained sediments is most likely caused by enhanced sea ice-rafted sediment input released under a strong West Greenland Current influence. Finally, a slight increase in IRD input during the last ∼2 ka BP is linked to the neoglacial re-advance of regional glaciers.