PALEOMAGNETISM OF A MIOCENE TRANSITION ZONE IN SOUTHEASTERN OREGON

A transition in the Earth's magnetic field, recorded in a sequence of basaltic lavas in southeastern Oregon (15.1 ± 0.3 m.y.), has been investigated. The reversal pattern is similar at the various sample sites (up to 55 miles apart) and the apparent paleo-intensity ranges from 0.5 Oe outside the transition to a minimum of 0.025 Oe inside the transition. This range is somewhat greater than that reported in other studies of transition zones. The similarity in transition pattern at the widely separated locations indicates that crustal magnetic anomalies could not have given rise to the recorded field. It is probable that the main dipole field and/or non-dipole centers were the primary features influencing the acquisition of TRM during the transition. © 1969.