Paleointensity during a chron C26r excursion recorded in west Greenland lava flows

Abstract

We present Thellier paleointensity data from Vaigat Formation lavas erupted during magnetochron C26r (age ∼60 Ma) in west Greenland. The lavas were emplaced in flow fields, as demonstrated by detailed field observations, the finding of consecutive lavas recording the same paleomagnetic field (intensity and direction), and similar composition suggestive of an identical magma-source. Of particular interest is a ∼ 140 m thick lava sequence of 31 lavas recording excursional directions that lie ∼60° away from the paleomagnetic pole. Thellier paleointensity determinations of good technical quality demonstrate an average paleofield of 35.0 ± 13.2 μT during the excursion, which is slightly stronger than the average 29.4 ± 14.5 μT stable polarity non-excursional field intensity. Relatively strong excursional field intensity has also been observed in lava sequences in Hawaii, Canary Island, and Japan, suggesting that some geomagnetic excursions represent periods of strong local nondipole fields rather than aborted reversals with significantly weakened dipole field. Copyright 2004 by the American Geophysical Union.