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Quaternary glaciation of central Banks Island, NT, Canada
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- Author / Creator
- Lakeman, Thomas Ryan
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The glacial geology and geomorphology of central Banks Island record the extent
and dynamics of the northwest Laurentide Ice Sheet (LIS) during Late Wisconsinan
glaciation. Additional stratigraphic exposures document Mid Quaternary
environmental changes. Detailed mapping and a new chronology indicate that the
island was inundated by the northwest LIS during the Late Wisconsinan. The
maximum limit of the ice sheet was offshore on the Beaufort Sea shelf, one of
several source regions for floating glacier ice that scoured the Arctic Ocean sea
floor to a depth of 450 m. Ice sheet retreat was underway by ~14 cal ka BP when
an ice stream withdrew rapidly from M’Clure Strait. A readvance or stillstand
13.75–12.75 cal ka BP resulted in deposition of widespread controlled moraines,
comprising the Jesse moraine belt on eastern Banks Island and adjacent Victoria
Island. This deposit records predominantly cold-based ice margins giving way to
polythermal bed conditions, which were conducive to widespread deposition of
controlled moraines and ice stream bedforms. The expansion of warm-based
thermal regimes in the northwest LIS followed ice sheet withdrawal from M’Clure
Strait and western Amundsen Gulf, suggesting a re-equilibration of regional ice
divides in response to rapidly changing ice sheet margins and surface gradients.
These reconstructed ice sheet dynamics provide new constraints for assessing the
sensitivity of the northwest LIS to past changes in climate and sea level.
Stratigraphic exposures at Morgan Bluffs on eastern Banks Island comprise an
archive of Mid to Late Quaternary environmental change. New, detailed
sedimentological analyses and stratigraphic investigations negate the previously
reported climatostratigraphy, which involved multiple glacial-interglacial cycles.
Instead, three distinct intervals of sedimentation are now recognized. The first
records the progradation of a delta, followed by aggradation of a braided river
valley perhaps ~1 Ma ago. The second documents a glacier advance across a
former marine delta more than 780 ka ago. The third succession is interpreted to
record sedimentation by an ice-contact delta into an ice-dammed lake during the
last deglaciation, ~12.75 cal ka BP. The revised stratigraphic framework adds
important new terrestrial observations to a sparse and fragmentary dataset of Arctic
environmental change. -
- Graduation date
- Fall 2012
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.