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Book Chapter

Systematic pattern of beach-ridge development and preservation: Conceptual model and evidence from ground penetrating radar

By
John W. Johnston
John W. Johnston
Department of Earth Sciences, University of Waterloo, 200 University Ave. W, Waterloo, Ontario N2L 3G1, Canada
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Todd A. Thompson
Todd A. Thompson
Indiana Geological Survey, Indiana University, 611 North Walnut Grove, Bloomington, Indiana 47405-2208, USA
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Steve J. Baedke
Steve J. Baedke
Department of Geology and Environmental Science, James Madison University, MSC 7703, Harrisonburg, Virginia 22807, USA
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Published:
January 01, 2007

A systematic pattern of beach ridges forming strandplains commonly fills embayments in the Great Lakes of North America. Ground penetrating radar (GPR) and vibracore results define a common preserved architecture inside beach ridges. Comparing the preserved architecture with a conceptual model of beach-ridge development explains the conditions responsible for their development and preservation. Great Lakes beach ridges are a product of a positive rate of sediment supply and a multidecadal fluctuation in lake level. Many shoreline behaviors occur throughout the development of a beach ridge, but not all successions originally formed by these behaviors are preserved. Beach ridges are stratigraphically separated by concave lakeward-dipping ravinement surfaces extending at depth below beach-ridge crests to the ground surface in adjacent landward swales. These surfaces are formed during rapid rises in water level, where previously laid deposits erode, forming a base for the beach-ridge core. As the rate of rise decreases and the water-level elevation approaches a highstand, the core of the ridge is built by vertical aggradation. Subsequent deposits build lakeward during progradation when water levels become stable, protecting the core from being eroded during future rapid rises in water level. Dune sand deposits on beach-ridge cores are stabilized by vegetation, and swales are commonly filled with organic material.

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Contents

GSA Special Papers

Stratigraphic Analyses Using GPR

Gregory S. Baker
Gregory S. Baker
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Harry M. Jol
Harry M. Jol
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Geological Society of America
Volume
432
ISBN print:
9780813724324
Publication date:
January 01, 2007

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