Early Holocene deglaciation of northern Hudson Bay and Foxe Channel constrained by new radiocarbon ages and marine reservoir correction

Abstract

Radiocarbon ages from Southampton Island (Canada) provide new chronological control on the deglaciation of Foxe Channel and northern Hudson Bay, a strategic area for understanding the demise of a marine-based portion of the Laurentide Ice Sheet. A regional marine reservoir age of 630 ± 45 yr and a reservoir offset (ΔR) of 263 ± 48 yr were calculated from two early to mid-Holocene terrestrial/marine radiocarbon age pairs. These values are consistent with corrections based on early 20th century mollusks suggesting that following deglaciation the oceanic conditions controlling the regional reservoir effect rapidly became similar to those of modern times. However, our ΔR value is 352 ± 52 yr less than another correction from eastern Foxe Basin, which may be affected by 14 C dilution from carbonate rocks. Our ΔR value is used to calibrate new marine radiocarbon ages which help further develop the deglaciation history of Southampton Island, especially along the north coast where deglaciation of Foxe Channel appears to have been completed by 8100–7800 cal yr BP (2σ). This provides key chronological constraints on the development of a long marine ice margin in southern Foxe Basin prior to the final breakup of the Foxe ice dome.

Deglaciation of the Laurentide Ice Sheet from the Last Glacial Maximum

“…Recession of the northern and eastern margins accompanied the continued rapid recession of the southern and western margins, although a series of moraine systems were built in some locations, which likely indicate temporary stabilisations (Dyke, 2004) or surges/ice streaming (Stokes and Clark, 2003). Final deglaciation of the remnant Keewatin and Foxe Domes (Dyke, 2004;Ross et al, 2012;Simon et al, 2014), left a remnant Labrador Dome that is thought to have deglaciated by around 6.7 ka (e.g. Ullman et al, 2016).…”

“…8d) (7 to 6 14 C ka), leaving residual ice caps on Baffin Island, Southampton Island, and Melville Peninsula that remain the last major remnants of the LIS. Deglaciation of the remnant Keewatin and Foxe Domes (Dyke, 2004;Ross et al, 2012;Simon et al, 2014) left a remnant Labrador Dome that has been estimated to contain a sea level equivalent of 3.6 ± 0.4 m at ~8.2 ka (Ullman et al, 2016) (Fig. 10).…”

Detrital carbonate peaks on the Labrador shelf, a 13–7ka template for freshwater forcing from the Hudson Strait outlet of the Laurentide Ice Sheet into the subpolar gyre

“…Carbonate-rich sediments would have continued to be released from retreat of a marine terminating ice margin in Foxe Basin between 8.1 and 7.8 cal ka BP (Ross et al, 2012) until as late as 6.5 14 C ka BP, estimated to be c. 7.45 cal ka BP (Dyke, 2004).…”

“…These events would have released detrital carbonate, meltwater and icebergs that could make their way to the Cartwright Saddle. The opening of Foxe Channel north of Southampton Island has recently been calibrated to occur between 8.1 and 7.8 ka at 2 sigma using a DR established by paired terrestrial and marine carbonate ages of 263 ± 48 (Ross et al, 2012) (Fig. 9).…”

“…McNeely et al (2006) and Coulthard et al (2010) used radiocarbon dates on museum specimens collected live to establish regional DR values for various areas of the Arctic; Vickers et al (2010) and Ross et al (2012) made paired comparisons of marine and terrestrial dates to establish marine reservoir corrections and DR in Foxe Basin; Barber et al (1999) and Roy et al (2011) used the key correlation between the 8.2 ka cooling in the Greenland ice cores with of the draining of glacial lakes Ojibway and Agassiz through Hudson Bay and Hudson Strait to derive DR values for radiocarbon dates associated with the flood event and consequent Tyrell Sea incursion. DR values are as high as 365 ± 115 14 C yrs for James Bay (Coulthard et al, 2010), and 352 ± 52 14 C yrs (Ross et al, 2012) or up to 615 14 C years during deglaciation (Vickers et al, 2010) for Foxe Basin.…”