Geomagnetism and Paleomagnetism/Marine Geology and Geophysics
Deep-sea sediment records of the Laschamp geomagnetic field excursion (∼41,000 calendar years before present)
Article first published online: 2 APR 2005
Copyright 2005 by the American Geophysical Union.
Journal of Geophysical Research: Solid Earth (1978–2012)
Volume 110, Issue B4, April 2005
How to Cite
2005), Deep-sea sediment records of the Laschamp geomagnetic field excursion (∼41,000 calendar years before present), J. Geophys. Res., 110, B04101, doi:10.1029/2003JB002943., , , and (
- Issue published online: 2 APR 2005
- Article first published online: 2 APR 2005
- Manuscript Accepted: 26 OCT 2004
- Manuscript Revised: 3 AUG 2004
- Manuscript Received: 16 DEC 2003
- Laschamp Excursion;
- paleomagnetic secular variation;
 We have recovered two new high-resolution paleomagnetic records of the Laschamp Excursion (∼41,000 calendar years B.P.) from deep-sea sediments of the western North Atlantic Ocean. The records document that the Laschamp Excursion was characterized locally by (1) declination changes of ±120°, (2) inclination changes of more than 140°, (3) ∼1200-year oscillations in both inclination and declination, (4) near 90° out-of-phase relationships between inclinations and declinations that produced two clockwise loops in directions and virtual geomagnetic poles (VGPs) followed by a counterclockwise loop, (5) excursional VGPs during both intervals of clockwise looping, (6) magnetic field intensities less than 10% of normal that persisted for almost 2000 years, (7) marked similarity in excursional directions over ∼5000 km spatial scale length, and (8) secular variation rates comparable to historic field behavior but persisting in sign for hundreds of years. All of these features, with the exception of anomalously large directional amplitude, are consistent with normal magnetic field secular variation. Comparison of our Laschamp Excursion paleomagnetic records with other late Quaternary excursion records suggests that there is a group of excursions, which we term class I, which have strikingly similar patterns of field behavior and likely share a common cause as part of the overall core dynamo process. Three general models of secular variation are described that can qualitatively produce class I excursions. On the basis of these observations we conclude that class I excursions, epitomized by the Laschamp Excursion, are more closely related to normal secular variation and are not necessarily a prelude to magnetic field reversal.