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Edens Road Marsh

USGS Topo Sheet: Cypress Island

Geographic coordinates: 48°33.13' N, 122°38.88' W

Paleoseismic record: Based on very limited reconnaissance, this site is unlikely to have preserved a record of recognizable paleoseismic events.

Setting: A 200-m-wide, 800-m-long area of small freshwater ponds and surrounding marsh lies landward of the highway embankment on the west coast of Guemes Island. The highway runs along a broad, low berm with several houses on its seaward side. Old, low (<1-m-high) dikes and the embankment restrict tidal access to what was probably once a lagoon with fringing marshes developed on low, sandy beach berms, dunes, and intervening tidal channels.

Stratigraphic description: Four gouge cores (2.5-cm-diameter) examined around the southwest edge of the marsh display a similar stratigraphy. The most interesting core showed:

    0-45 cm crumbly, fibrous peaty loam

    45-55 cm sandy, clayey silt

    55-72 cm crumbly, fibrous peaty loam

    72-76 cm humified peaty mud

    76-79 cm sandy, humified peaty mud

    79-93 cm interbedded silty clay and clean sand

    93-98+ cm clean, medium to fine sand

Paleontology/Paleoecology: No paleontologic work has been completed.

Geologic interpretation: Lithologic changes in at least two of the cores suggest rapid flooding of part of the marsh (55 cm depth in above core), probably in the past few hundred years. However, the sandy substrate, probable low elevation of the original protecting beach berm, complex geomorphology of the site, and prior development of the berm and part of the marsh mean that distinguishing among processes that might produce such lithologic changesæ coseismic land-level changes, tsunamis, storms, or diking of the marshæ will be difficult.

Date of last work at site: September 1997

Status of work: No additional work is planned.

Published information on this site: None

Investigators: A. Nelson

Please use the following format in citing information from this page:

Nelson, A.R., Edens Road Marsh, in Bucknam, R.C., compiler, 1999, Atlas of reconnaissance data from paleoseismic studies in the Puget Sound region, Washington: U.S. Geological Survey Web Page, http://earthquake.usgs.gov/regional/pacnw/paleo/atlas.html.

This URL is: http://earthquake.usgs.gov/regional/pacnw/paleo/reports/edenroad.htm
Modified July 29, 2002 by Susan Rhea