Magnetostratigraphy of the Columbia River basalt, Pasco Basin and vicinity, Washington
Technical Report
·
OSTI ID:5171269
A paleomagnetic study was performed on about 500 surface and subsurface samples of the Columbia River Basalt Group from the Pasco Basin and vicinity, southeastern Washington. This study also included reanalysis and integration of paleomagnetic data collected during three previous paleomagnetic investigations. Emphasis was placed on testing and extending the magnetostratigraphic interpretation of the Columbia River basalts beneath the Hanford Site. A consistent magnetostratigraphy of Grande Ronde Basalt emerges from the surface and core hole paleomagnetic data. A change from reversed polarity (below) to normal polarity (above) occurs at a depth of approx. 1500 ft below the Vantage horizon. This polarity change is the R/sub 2/-N/sub 2/ contact, previously mapped in surface outcrops on the Columbia Plateau. Within the two magnetozones of the upper Grande Ronde Basalt, between-flow inclination differences of up to 60/sup 0/ probably reflect the Miocene geomagnetic secular variation. These distinctive changes in paleoinclination permit subdivision of the Grande Ronde-R/sub 2/ magnetozone into three magnetic intervals (designated GR-R/sub 2/..cap alpha.. through ..gamma..) and of the Grande Ronde-N/sub 2/ magnetozone into five magnetic intervals (GR-N/sub 2/..cap alpha.. through epsilon).The Wanapum and Saddle Mountains Basalts contain at least four magnetozones and large variations in magnetic susceptibility as well as in inclination. In the Pasco Basin core holes, the consistency of paleomagnetic directions at equivalent stratigraphic horizons indicates that these holes penetrated few if any dikes.
- Research Organization:
- Rockwell International Corp., Richland, WA (USA). Energy Systems Group
- DOE Contract Number:
- AC06-77RL01030
- OSTI ID:
- 5171269
- Report Number(s):
- RHO-BWI-C-110; ON: DE82017211
- Country of Publication:
- United States
- Language:
- English
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