Geologic field trip guide for Cenozoic stratigraphy of southwestern Washington
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Abstract
This summary of southwestern Washington stratigraphy describes the principal Tertiary formations comprising the Cenozoic sequences. A field trip road log provides directions for access to type and/or reference localities for each formation discussed.
Tertiary rocks of southwestern Washington, measuring nearly 13,000 feet in thickness, are mapped as thirteen formational units. These units crop out within several structural basins formed along the tectonically active Pacific margin of the North American Plate. Thick Quaternary sands and gravels of glacial and fluvial origin and a heavy vegetational cover restrict exposures to stream and river banks, highway, road and railroad cuts, and occasional steep hillsides.
The Tertiary strata are predominantly marine sedimentary rocks with interbedded volcanics and eastwardly increasing amounts of nonmarine strata. Age equivalent and genetically similar sequences occur throughout the Coast Ranges of western Oregon and Washington.
Study Area
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Geologic field trip guide for Cenozoic stratigraphy of southwestern Washington |
| Series title | Open-File Report |
| Series number | 80-362 |
| DOI | 10.3133/ofr80362 |
| Year Published | 1980 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Description | 72 p. |
| Country | United States |
| State | Washington |
| Other Geospatial | southwestern Washington |
| Google Analytic Metrics | Metrics page |