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The Wave-Dominated William River Delta, Lake Athabasca, Canada: Its Morphology, Radar Stratigraphy, and History

By
Derald G. Smith
Derald G. Smith
Department of Geography, University of Calgary, Calgary, Alberta T2N1N4, Canada, e-mail: dgsmit@ucalgary.ca
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Harry M. Jol
Harry M. Jol
Department of Geography, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin 54702, U.S.A., e-mail: jolhm@uwec.edu
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Norman D. Smith
Norman D. Smith
Department of Geosciences, University of Nebraska, Lincoln, Nebraska 68588, U.S.A., e-mail: nsmith3@unl.edu
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Raymond A. Kostaschuk
Raymond A. Kostaschuk
Department of Geography, University of Guelph, Guelph, Ontario N1G 2W1, Canada, e-mail: rkostasc@uoguelp.ca
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Cheryl M. Pearce
Cheryl M. Pearce
Department of Geography, University of Western Ontario, London, Ontario N6A 5C2, Canada, e-mail: cpearce@uwo.ca
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Published:
January 01, 2005

Abstract

The wave-dominated Holocene William River delta, located along the south coast of Lake Athabasca, northern Saskatchewan, is a lobate sand body 9 km long by 8 km wide by 15-22 m thick. Mean lake elevation is 209 m and fluctuates ± 1.5 m (1810-2000). Periodic strong winds, waves, and currents generated in deep water (50-100 m)with long fetches (50-110 km) shape the delta morphology and determine its internal sedimentary structure. Its surface is dominated by multiple arcuate sets of eolian-dune-capped beach ridges separated by peatlands. A one-kilometer-wide arcuate, subaqueous shelf is covered by multiple (up to 19) offshore bars and troughs in water depths to 5.5 m. Farther offshore, a 1 to 7° foreset slope plunges to a depth of 15 to 17 m. Lakeward from the toe of the foreset slope, gently sloping (0.0072 or 7.2 m/km) bottomset beds of thin sand lenses interfinger with lacustrine mud. Luminescence and radiocarbon dates suggest that the rate of delta progradation has declined an order of magnitude from an initial 1.4 m yr-1 (9800 to 7000 cal yr BP) to the present 0.16 m yr-1, because of reduced fluvial sediment influx from a nearby depleting eolian dune field and exponentially larger volumes of sand required to maintain constant rates of linear expansion.

Radar stratigraphic profiles to depths of 15-22 m along depositional dip and strike indicate lakeward-inclined erosional surfaces and lensoid sand bodies. Nested within these lenses are “J-shaped” reflections which represent progradational sequences deposited by annual to decadal storms. Several gently basinward-dipping (< 1°) erosional surfaces between 5 and 14 m deep are interpreted to have formed by severe millennial-frequency storms.

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Contents

SEPM Special Publication

River Deltas–Concepts, Models, and Examples

Liviu Giosan
Liviu Giosan
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Janok P. Bhattacharya
Janok P. Bhattacharya
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SEPM Society for Sedimentary Geology
Volume
83
ISBN electronic:
9781565762190
Publication date:
January 01, 2005

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