Mackenzie Glacial Outburst Floods into the Arctic Ocean 13,000-10,000 Years ago
Abstract
An unconformity with an area of at least 9400 km2 and a relief of about 100 m in the eastern Beaufort continental shelf and adjacent coastlands near the Mackenzie Delta is attributed to fluvial erosion during deglaciation of the northwest Laurentide Ice Sheet. On northeast Richards Island, the unconformity is overlain by a fluvial gravel or gravelly lag of pebble to boulder-size material. Optical dating of eolian sand above and below the unconformity constrains erosion and deposition to between about 13.0 and 10.1 ka. Additional optical dates from fluvial sand above gravel indicate an age of about 11.8 ka. If the active margin of the Laurentide Ice Sheet had retreated nearly 600 km southeast of Richards Island by 13 ka, as shown in the Dyke et al. (2003) reconstruction of deglaciation, then a local source of glacial meltwater is discounted. Instead, the fluvial activity was likely associated with outburst flooding from distant glacial lakes into the Arctic Ocean. An earlier episode of flooding shortly after about 13 ka possibly coincided with the onset of the Younger Dryas, and a later episode between about 11.8 ka and 10.1 ka possibly coincided with the onset of the Pre-Boreal Oscillation at about 11.3 ka. The new geological evidence from the Mackenzie Delta region supports recent proposals that massive discharges of glacial meltwater issued northward along the Mackenzie River during deglaciation of the Laurentide Ice Sheet.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMPP51A1474M
- Keywords:
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- 0726 Ice sheets;
- 1105 Quaternary geochronology;
- 1621 Cryospheric change (0776);
- 1630 Impacts of global change (1225);
- 9315 Arctic region (0718;
- 4207)