Early Holocene delevelling and deglaciation of the Cumberland Sound region, Baffin Island, Arctic Canada

Abstract

Radiocarbon, cosmogenic surface exposure, and relative sea-level data are used to examine deglaciation and glacioisostatic adjustment of Cumberland Sound and Cumberland Peninsula, and southeastern Baffin Island, in the context of a new model for the glacial history of the eastern Canadian Arctic. Over the last decade, a multidisciplinary effort on easternmost Baffin Island has documented far greater ice expansion during the last glacial maximum than previously believed, including low gradient glaciation in marine embayments coexisting with ice free or thin cold-based ice on adjacent upland crystalline terrain. This study documents that the Cumberland Sound region underwent about twice as much glacioisostatic movement during the last glacial maximum as shown in previous reconstructions. However, the loading impact of the Laurentide Ice Sheet and local glaciation on adjacent Cumberland Peninsula was limited; the mapped zero isoline on emergence shows that postglacial eustatic rise exceeded glacial isostatic uplift for much of the eastern peninsula, a finding that is consistent with that of prior studies. The center of loading and the major source of glacial ice for the entire Cumberland Sound region were Foxe Basin and western Baffin Island. Strandlines dated 10,500 and 8500 1 4 C yr B.P. show that slow deglaciation of Cumberland Sound was punctuated by at least two periods of faster grounding line retreat. Coastal southeastern Cumberland Peninsula was deglaciated before 9400 1 4 C yr B.P., and other areas surrounding Cumberland Sound were deglaciated after ca. 9000 1 4 C yr B.P.; these land areas experienced relatively slow glacial retreat and restrained rebound. Cosmogenic surface exposure ages on glacially-scoured bedrock support the 1 4 C-based inferred timing for deglaciation of the sound, although inheritance of nuclides from prior exposure is evident in samples, indicating limited bedrock erosion in many areas. For central Cumberland Sound, a rapid rise of relative sea-level of ∼4-5 m/100 1 4 C yr (4-6 m/100 yr) and a half life for crustal response of <720 1 4 C yr (<1400 yr) are consistent with those values obtained in other studies of isostatic adjustment around the edges of the former Northern Hemisphere ice sheets where lithospheric influences were relatively dominant.