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Annual layers revealed by GPR in the subsurface of a prograding coastal barrier, southwest Washington, U.S.A

Journal of Sedimentary Research

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, , , ,

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Abstract

The southwest Washington coastline has experienced extremely high rates of progradation during the late Holocene. Subsurface stratigraphy, preserved because of progradation and interpreted using ground-penetrating radar (GPR), has previously been used successfully to document coastal response to prehistoric storm and earthquake events. New GPR data collected at Ocean Shores, Washington, suggest that the historic stratigraphy of the coastal barrier in this area represents a higher resolution record of coastal behavior than previously thought. GPR records for this location at 200 MHz reveal a series of gently sloping, seaward-dipping reflections with slopes similar to the modern beach and spacings on the order of 20-45 cm. Field evidence and model results suggest that thin (1-10 cm), possibly magnetite-rich, heavy-mineral lags or low-porosity layers left by winter storms and separated by thick (20-40 cm) summer progradational sequences are responsible for generating the GPR reflections. These results indicate that a record of annual progradation is preserved in the subsurface of the prograding barrier and can be quantified using GPR. Such records of annual coastal behavior, where available, will be invaluable in understanding past coastal response to climatic and tectonic forcing. ?? 2004.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Annual layers revealed by GPR in the subsurface of a prograding coastal barrier, southwest Washington, U.S.A
Series title:
Journal of Sedimentary Research
Volume
74
Issue:
5
Year Published:
2004
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
690
Last page:
696
Number of Pages:
7