Paleosecular variation from Easter Island revisited: modern demagnetization of a 1970s data set

Sixty-two Brunhes age lava flows from Easter Island in the Eastern Pacific Ocean, collected and processed for paleomagnetic and secular variation studies in the 1970s, have been reprocessed to meet current standards of demagnetization. Alternating field demagnetization in 7–10 steps was performed on all samples previously undemagnetized and characteristic directions determined from principal component analysis. The final data set gives a mean direction of I=−46.1° and D=357.4° with α95=3.9° Eliminating sites with 95% confidence circles greater than 10.0° gave an angular dispersion of virtual geomagnetic poles (VGPs) of 14.1° with respect to the rotation axis. This value is slightly larger than that determined prior to detailed demagnetization, and agrees with values predicted for this latitude by Model G. There is no compelling evidence from this study supporting the existence of a secular variation low in the southeastern Pacific region.