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U.S. Geological Survey Scientific Investigations Map 3181

Geologic Map of the Suquamish 7.5’ Quadrangle and Part of the Seattle North 7.5’ x 15’ Quadrangle, Kitsap County, Washington

By Ralph A. Haugerud and Kathy Goetz Troost

Summary

The Suquamish 7.5’ quadrangle is in the center of the Puget Lowland, Washington. The quadrangle contains the northern two-thirds of Bainbridge Island and adjacent parts of the Kitsap Peninsula. Puget Sound and contiguous waterways form 35 percent of the map area. Maximum elevation is 137 m in the northwest corner of the quadrangle, west of Suquamish; the modal elevation is 44 m. The center of the quadrangle is 20 km west-northwest of downtown Seattle. Winslow, in the southeast corner of the quadrangle, is a 35-minute ferry ride from Seattle.

The Suquamish quadrangle lies within the Salish Lowland physiographic province (Haugerud, 2004), a broad region in the forearc of the Cascade Volcanic Arc that extends from south of Olympia, Washington, to north of Campbell River, British Columbia, and includes both the Puget Lowland of western Washington and the Georgia Depression of northwestern Washington and southwestern British Columbia. To the east are the Cascade Range and Coast Mountains; to the west is the outer-arc high of the Coast Ranges. The Salish Lowland is the locus of late Cenozoic subsidence: Jones (1996) indicates as much as 1 km of unconsolidated fill beneath some areas. The Lowland is crossed by east-west topographic highs formed by bedrock uplifts. A northern San Juan high divides the Lowland into Georgia Depression and Puget Lowland subprovinces. A southern high, which lies athwart the south end of Bainbridge Island immediately south of the map area, coincides with the Seattle Fault Zone along which uplift has brought Eocene rocks to elevations of 800–1,200 m, 8–10 km higher than equivalent strata in the floor of the Seattle structural basin that underlies central and northern Bainbridge Island and areas to the east (Brocher and others, 2001; Blakely and others, 2002). Deformation along the Seattle Fault appears to be driven by north-south shortening of the Cascade forearc (Wells and others, 1998).

Pleistocene glacial deposits underlie most of the map area. Most extensive are the various members of the Vashon Drift, deposited in the Vashon stade of the Fraser Glaciation of Armstrong and others (1965) between about about 17,000 years ago.

This study was undertaken in response to (1) awareness of the hazard posed by future earthquakes in the Seattle Fault Zone, at the south edge of the quadrangle, and the need to marshal geologic evidence for the rate and style of deformation; (2) increasing population on Bainbridge Island and consequent pressure on groundwater resources; (3) concern about landslide hazards; and (4) awareness of the role that the nearshore zone plays in supporting marine resources.

Thumbnail of and link to report PDF (21.4 MB)

         Files for viewing and printing:

  • Pamphlet PDF (9 pages, 344 kB)
  • Map PDF (48" x 31", 12.9 MB)

         Data:

  • Readme TXT (4 kB)
  • Metadata folder (2 files, 24 kB)
  • GIS database (7-MB ZIP file that expands to a 18-MB folder. NCGMP09-style ArcGIS geodatabase and ancillary files. Includes some base materials)
  • Simple version of GIS database (861-KB ZIP file that opens into a 6.7-MB directory. Simple shapefile version of GIS database. Easy to use but incomplete. No base materials)
  • Open version of GIS database (882-KB ZIP file that opens into a 5.7-MB directory. Database transcribed to open-format shapefiles, dbf files, and delimited text files. Complete and difficult to use. No base materials)
  • This report is available only on the Web.

For additional information:
Contact Information, Geology, Minerals, Energy, and Geophysics Science Center—Menlo Park
U.S. Geological Survey
345 Middlefield Road
Menlo Park, CA 94025-3591
http://geomaps.wr.usgs.gov/gmeg/

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Suggested citation:

Haugerud, R.A., and Troost, K.G., 2011, Geologic map of the Suquamish 7.5’ quadrangle and part of the Seattle North 7.5’ x 15’ quadrangle, Kitsap County, Washington: U.S. Geological Survey Scientific Investigations Map 3181, scale 1:24,000, available at http://pubs.usgs.gov/sim/3181/.




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