| Title | Marine record of late-glacial readvance and last recession of Laurentide ice, inner Frobisher Bay, Baffin Island |
| |
| Author | Deering, R; Bell, T; Forbes, D L |
| Source | Canadian Journal of Earth Sciences 2021 p. 1-18, https://doi.org/10.1139/cjes-2021-0004  Open Access |
| Image |  |
| Year | 2021 |
| Alt Series | Natural Resources Canada, Contribution Series 20200768 |
| Publisher | Canadian Science Publishing |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Nunavut |
| NTS | 25N/07; 25N/08; 25N/09; 25N/10; 25N/15; 25N/16 |
| Area | Frobisher Bay; Baffin Island |
| Lat/Long WENS | -68.8333 -68.0000 63.8333 63.3333 |
| Subjects | marine geology; sedimentology; marine environments; ice; glaciomarine deposits; glaciology; marine sediments; Laurentian Ice-Sheet |
| Illustrations | location maps; tables; bathymetric profiles; images; stratigraphic columns |
| Program | Public Safety Geoscience Assessing landslides and marine geohazards |
| Released | 2021 08 25 |
| Abstract | The Cockburn Substage readvance marks the last major late-glacial advance of the northeast sector of the Laurentide Ice Sheet on Baffin Island. The causes of this abrupt, late reversal of retreat are
still unclear, but greater chronological controlmay provide some insight. To date, the literature has focused on the large terminalmoraines in the region, providing a date of readvance (circa 9.5-8.5 ka cal BP). In Frobisher Bay, the Cockburn
Substage readvance and recession onshore are marked by a series of moraines spread over 20 km along the inner bay. Acoustic marine mapping reveals five distinct transverse ridges, morphologically suggestive of grounding-zone wedges, and two later
fields of DeGeer moraines on the floor of the inner bay. These indicate that the style of ice retreat (beginning no later than 8.5 ka cal BP) changed over time from punctuated recession of a floating ice front (20 km over >680 years, with four
pauses) to more regular tidewater icefront retreat, reaching the head of the bay 900 years or more after withdrawal from the outer Cockburn limit. The established chronology for final recession in the region is based largely on radiocarbon dating of
bulk shell samples and single shells of deposit-feeding molluscs, notably Portlandia arctica, affected by old carbon from carbonate-rich sediments. Sedimentary analysis and judicious sampling for 14C dating of glaciomarine and marine facies in seabed
sediment cores enables development of a late- and post-glacial lithostratigraphy that indicates final withdrawal of ice from the drainage basin by 7 ka cal BP. |
| Summary | (Plain Language Summary, not published)
The last glacial readvance of the continental (Laurentide) continental ice sheet from inner Frobisher Bay (near Iqaluit, Nunavut) occurred before 9400
years ago and the ice had disappeared from the bay by 7800 years before present. Seabed mapping and sediment coring show how the style of retreat changed over time from a step process, forming five large, distinct, moraine ridges to a regular
tidewater ice-front retreat forming numerous small subparallel ridges known as DeGeer moraines. Radiocarbon chronology from fossil molluscs in the cores refines the timing of these processes. |
| GEOSCAN ID | 328149 |
|
|