LOOKING FOR EVIDENCE OF DEGLACIATION DURING MIS 3 WITHIN THE BOOTHIA-LANCASTER ICE STREAM

The Foxe Dome ice is drained by ice streams exiting through by both Hudson Strait and Boothia Bay-Lancaster Strait as well as numerous smaller ice outlets through fiords on eastern Baffin Island. During the deglaciation of MIS 2 ice, the Gulf of Boothia/Lancaster Ice Stream retreated about 1 ka before Hudson’s Strait Ice stream. The Hudson Bay stratigraphy records has been recently under renewed scrutiny regarding the possible deglaciation event during MIS 3, an idea which is not making consensus so far based on contradictory data and interpretations. It could be useful to look into the Boothia-Lancaster Ice Stream area stratigraphic record for evidence of deglaciation during MIS 3.

The Boothia Bay-Lancaster Strait Ice Stream behaviour during MIS 3-4-5a is largely unknown, with sites with pre-LGM sediments have few reliable geochronological measurements. To resolve this issue, a series of new Single-Grain Infrared Stimulated Luminescence (SG-IRSL) dates (16 sites) from glaciomarine, marine and glaciofluvial sediments were conducted. Ages between 30 to 80 ka were measured for interstadial sediments (MIS 3-4-5a) on the northeastern coast of Baffin Island and Bylot Island. West of Baffin Bay coastal exposures, in the region draining the massive Boothia-Lancaster Ice Stream, 130 ka (MIS 5e) dates were measured in interglacial sediments on two sites (Aua River and Paisley River). One intermediate site, west of Bylot Island, show 130 ka (MIS 5e) age at the bottom of section and 80ka (MIS 5a) at the top of the section. In those sediments, the presence of numerous shells with ages > 40ka, and a few with ages of 25-50 ka, are thought to be due to contamination with modern carbon (for example at Paisley River sections).

The absence of interstadial sediments dated MIS 3-4-5a in the Gulf of Boothia-Lancaster Sound area suggest that this area was covered by ice during that period. If this is true, then the proposed deglaciation of Hudson Bay during MIS 3 would imply different a contrasting Foxe Dome response to external drivers (climatic, sea level, isostatic rebound, temperature of the ground) during MIS 3 versus during MIS 2. Furthermore, the co-existence of uncoupled ice streams within the same ice dome for a long period of time during MIS 3 would be problematic, and would need to be explained with glaciological modelling.