Remanent magnetism of the Twin Sisters Dunite Intrusion and implications for the tectonics of the western Cordillera |
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| Authors: | Myrl E Beck |
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| Institution: | Department of Geology, Western Washington State College, Bellingham, Wash. USA |
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| Abstract: | The Twin Sisters Dunite Intrusion has a homogeneous remanent magnetization directed nearly due east and inclined about 60° below the horizontal. It was emplaced in the Early Tertiary as a solid intrusion, but probably was above its Curie temperature at the time and so became magnetized substantially in situ. If so, it must have undergone considerable tectonic disturbance subsequent to emplacement and magnetization, including an important component of clockwise rotation. Examination of paleomagnetic data for the westernmost Cordillera shows that an abnormal number of rock bodies have discordant directions of remanent magnetization, mostly clockwise rotations of declination, flattened inclinations, or both. This sense of discordance in turn suggests that the western margin of the North American plate may have been deformed intermittently by right-lateral shear for at least some few tens of millions of years. |
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