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AGU: Journal of Geophysical Research, Solid Earth

 

Keywords

  • Laschamp Excursion
  • paleomagnetic secular variation
  • paleointensity

Index Terms

  • Geomagnetism and Paleomagnetism: Core processes
  • Geomagnetism and Paleomagnetism: Geomagnetic excursions
  • Geomagnetism and Paleomagnetism: Paleointensity
  • Geomagnetism and Paleomagnetism: Paleomagnetic secular variation
  • Geomagnetism and Paleomagnetism: Reversals: process, timescale, magnetostratigraphy
Abstract
Cited By (19)
 

Abstract

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, B04101, 15 PP., 2005
doi:10.1029/2003JB002943

Deep-sea sediment records of the Laschamp geomagnetic field excursion (∼41,000 calendar years before present)

Steve P. Lund

Department of Earth Sciences, University of Southern California, Los Angeles, California, USA

Martha Schwartz

Department of Earth Sciences, University of Southern California, Los Angeles, California, USA

Lloyd Keigwin

Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA

Thomas Johnson

Large Lakes Observatory, University of Minnesota at Duluth, Duluth, Minnesota, USA

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.

Received 16 December 2003; accepted 26 October 2004; published 2 April 2005.

Citation: Lund, S. P., M. Schwartz, L. Keigwin, and T. Johnson (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.

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