Pre‐Younger Dryas resurgence of the southwestern margin of the Cordilleran ice sheet, British Columbia, Canada

Abstract

Clague, J. J., Mathewes, R. W., Guilbault, J.‐P., Hutchinson, I. & Ricketts, B. D. 1997 (September): Pre‐Younger Dryas resurgence of the southwestern margin of the Cordilleran ice sheet, British Columbia, Canada. Boreas, Vol. 26, pp. 261–278. Oslo. ISSN 0300–9483. A lobe of the Cordilleran ice sheet readvanced into the central Fvaser Lowland, southwestern British Columbia, Canada, on at least two occasions near the end of the last glaciation. This ice also flowed into the previously deglaciated, lower reaches of mountain valleys adjacent to the Fraser Lowland and into Washington state. The first of these advances occurred before about 11900 BP and ended with glacier retreat and the establishment of lodgepole pine forest on newly deglaciated terrain. Parts of this forest were overridden by ice during a second advance, shortly after 11300 BP. The younger advance is most likely older than the Younger Dryas Chronozone (11000–10000 BP) and may correlate with an intra‐Allerad cooling event (the Killarney‐Gerzensee oscillation). The older advance may have occurred during the Oldest Dryas or Older Dryas cold period. Non‐climatic factors could also be involved, as emergence of the Fraser Lowland before the older advance greatly reduced or eliminated calving at the glacier margin and thus altered the mass balance of the ice lobe.

Deglaciation of the Cordillera of Western Canada at the end of the Pleistocene

“…Most re-advances affected relatively small areas and may not have been synchronous from one region to another. Minor resurgences in the central Fraser Lowland east of Vancouver are particularly well documented (Armstrong, 1981;Clague et al, 1997;Kovanen, 2002). At least one of these advances happened during or before the Older Dryas interval; another may have happened during an intra-Allerød cold interval; and a third likely dates to the Younger Dryas interval.…”

“…An implication of this study, as well as those of Clague et al (1997) and Kovanen (2002) in Fraser Lowland, is that the southern Coast Mountains had a large cover of ice, with some glaciers reaching to sea level as late as 13,000 years ago (see below).…”

“…Active ice probably persisted longest in high mountain valleys, but these remnant glaciers may have coexisted with large masses of dead ice in some areas of the British Columbia interior. Fulton, 1969 Disintegration of the Cordilleran Ice Sheet was interrupted repeatedly by glacier readvances (Alley and Chatwin, 1979;Clague, 1984Clague, , 1989Clague et al, 1997;Clague, 2002a, 2002b;Kovanen, 2002;Lakeman et al, 2008). Most re-advances affected relatively small areas and may not have been synchronous from one region to another.…”

Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene

“…Mid MIS 2 was marked by the advance and retreat of the CIS during the Vashon stade, and ended in the lowlands during a marine incursion into western valleys during the Everson interstade (Dethier et al, 1995). Late MIS 2 was dominated by the final decay of the ice sheet in higher mountain valleys, and included late advances by the CIS (Sumas stade) (Clague et al, 1997) and alpine glaciers (Porter et al, 1983;Osborn et al, 2012).…”

“…northern Europe from 14.1 to 11.6 ka (Stuiver et al, 1995;Clague et al, 1997;Friele and Clague, 2002;Kovanen and Slaymaker, 2005;Riedel, 2007;Osborn et al, 2012).…”