Geologic map of the Ridgefield Quadrangle, Clark and Cowlitz Counties, Washington.
Evarts, Russell C; Dinterman-Philip (compiler); Block-Jessica (compiler) (2004) Geologic map of the Ridgefield Quadrangle, Clark and Cowlitz Counties, Washington. Scientific Investigations Map. 2004.
| Authors | Evarts, Russell C; Dinterman-Philip (compiler); Block-Jessica (compiler) |
|---|---|
| Year | 2004 |
| Title | Geologic map of the Ridgefield Quadrangle, Clark and Cowlitz Counties, Washington. |
| Source | Scientific Investigations Map. 2004. |
| Publisher | U. S. Geological Survey, United States. Pages: 22, 1 sheet. 2004. |
| Document type | Map; Serial; Report |
| GeoRef | 2005-022484 |
| Keywords | areal-geology; bedrock-; Clark-County-Washington; Columbia-River-basin; Cowlitz-County-Washington; geologic-maps; landforms-; lithostratigraphy-; maps-; petrology-; Ridgefield-Quadrangle; stratigraphic-units; surficial-geology; tectonic-elements; United-States; USGS-; volcanism-; Washington- |
Abstract
This map is located just east of the Columbia River about 30 km north of Portland, Oregon. Bedrock, exposed only in the north part of the quadrangle, consists of eroded and tilted Paleogene volcanic rocks unconformably overlain by lava flows of the Miocene Columbia River Basalt Group and by sedimentary deposits that accumulated in the late Neogene Portland Basin. In most areas, the older deposits are covered by either slack-water silt deposited by latest Pleistocene Missoula floods or by Holocene alluvium.
8 samples from this reference
| Sample | Rock name | Major | Trace | Isotope |
|---|---|---|---|---|
| 97LC-Q62B2 | Andesite | yes | yes | |
| 98LC-Q281C | Andesite | yes | yes | |
| 98LC-Q281B | Andesite | yes | yes | |
| 01LC-Q459C | Andesite | yes | yes | |
| 00LC-Q422B | Andesite | yes | yes | |
| 97LC-Q61B | Dacite | yes | yes | |
| 99LC-Q397 | Basaltic-andesite | yes | yes | |
| 99LC-Q428 | Basaltic-andesite | yes | yes |