Paleomagnetic study of recent Cascade lavas, Three Sisters, Oregon

Abstract

The natural remanent magnetization of 94 oriented cores from nine recent lava flows was measured. The field area is located in the Three Sisters area of the Oregon Cascades. The maximum possible age range for the flows is from 300 to 12,000 years B.P.; eight of the nine flows are younger than 3850 years. The mean direction of magnetization (D = 2.2°, I = +49.6°, α95 = 5.2°) is statistically distinct from the axial geomagnetic dipole field (D = 0°, I = +62.9°). It is not clear whether this mean direction is a significant departure of the main geomagnetic field from an axial direction or part of the ‘normal’ secular change.