Journal
QUATERNARY SCIENCE REVIEWS
Volume 29, Issue 9-10, Pages 1288-1300Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.quascirev.2010.02.015
Keywords
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Funding
- Natural Science and Engineering Research Council of Canada
- Polar Continental Shelf Program
- Alberta Ingenuity New Faculty Award
- Yukon Geological Survey
- Northern Science Training Program
- Canadian Circumpolar Institute
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The Eagle River spillway and braid delta complex provide a record of the maximum extent of the northwest Laurentide Ice Sheet and diversion of meltwater from Bonnet Plume Basin into the interior basins of non-glaciated northern Yukon. Development of the spillway can be characterized in three distinct zones based on the distribution of erosion and deposition along each reach: erosion-dominated channel initiation and incision; followed by channelization and coarse clastic deposition along channel margins and into tributary valleys; and lastly, fine-grained deltaic and lacustrine sedimentation in the lower channel reach. Deltaic sedimentation within the spillway is crudely-coarsening upward from alternating beds of massive clay and silt to ripple-cross-bedded sand. All sediments occur in rapidly-aggrading forms with no evidence for a significant hiatus in deposition. Radiocarbon ages on woody plant macrofossils and spruce needles are non-finite, while radiocarbon ages on macrofossils from herbaceous plant taxa and insects with 'steppe-tundra' ecological affinity from the upper part of the delta range from 15 840 +/- 90 to 21 600+/- 1300 C-14 yr BP. These ages, coupled with the rapidly-aggrading nature of the delta sediments and landform, suggest an age of ca 15-16 000 C-14 yr BP. Non-finite and mixed ages underscore the significant problem of reworked, well-preserved macrofossils in Arctic environments and the need for careful selection of both fragile and ecologically-representative macrofossils to establish reliable chronologies. (C) 2010 Elsevier Ltd. All rights reserved.
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