Baffin Bay paleoenvironments in the LGM and HS1: Resolving the ice-shelf question

• Published in: Marine Geology
• Main Authors: Jennings, A., Andrews, J., Ó Cofaigh, C., St-Onge, G., Belt, S., Cabedo-Sanz, P., Pearce, C., Hillaire-Marcel, C., Campbell, C.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 2018
• Subjects: Baffin Bay; Greenland; Baffin; Davis Strait; greenlandic; Ice Sheet; Ice Shelf; Sea ice
• Online Access: http://dro.dur.ac.uk/23111/; http://dro.dur.ac.uk/23111/1/23111.pdf; https://doi.org/10.1016/j.margeo.2017.09.002

Core HU2008029-12PC from the Disko trough mouth fan on the central West Greenland continental slope is used to test whether an ice shelf covered Baffin Bay during the Last Glacial Maximum (LGM) and at the onset of the deglaciation. We use benthic and planktic foraminiferal assemblages, stable isotope analysis of planktic forams, algal biomarkers, ice-rafted detritus (IRD), lithofacies characteristics defined from CT scans, and quantitative mineralogy to reconstruct paleoceanographic conditions, sediment processes and sediment provenance. The chronology is based on radiocarbon dates on planktic foraminifers using a ∆ R of 140 ± 30 14C years, supplemented by the varying reservoir estimates of Stern and Lisiecki (2013) that provide an envelope of potential ages. HU2008029-12PC is bioturbated throughout. Sediments between the core base at 11.3 m and 4.6 m (LGM through HS1) comprise thin turbidites, plumites and hemipelagic sediments with Greenlandic provenance consistent with processes active at the Greenland Ice Sheet margin grounded at or near the shelf edge. Abundance spikes of planktic forams coincide with elevated abundance of benthic forams in assemblages indicative of chilled Atlantic Water, meltwater and intermittent marine productivity. IRD and IP25 are rare in this interval, but brassicasterol, an indicator of marine productivity reaches and sustains low levels during the LGM. These biological characteristics are consistent with a sea-ice covered ocean experiencing periods of more open water such as leads or polynyas in the sea ice cover, with chilled Atlantic Water at depth, rather than full ice-shelf cover. They do not support the existence of a full Baffin Bay ice shelf cover extending from grounded ice on the Davis Strait. Initial ice retreat from the West Greenland margin is manifested by a pronounced lithofacies shift to bioturbated, diatomaceous mud with rare IRD of Greenlandic origin at 467 cm (16.2 cal ka BP; ∆ R = 140 yrs) within HS1. A spike in foraminiferal abundance and ocean warmth indicator ...