Very rapid geomagnetic field change recorded by the partial remagnetization of a lava flow
Article first published online: 10 NOV 2010
Copyright 2010 by the American Geophysical Union.
Geophysical Research Letters
Volume 37, Issue 21, November 2010
How to Cite
2010), Very rapid geomagnetic field change recorded by the partial remagnetization of a lava flow, Geophys. Res. Lett., 37, L21308, doi:10.1029/2010GL044286., and (
- Issue published online: 10 NOV 2010
- Article first published online: 10 NOV 2010
- Manuscript Accepted: 20 AUG 2010
- Manuscript Revised: 30 JUL 2010
- Manuscript Received: 10 JUN 2010
 A new paleomagnetic result from a lava flow with a distinctive, two-part remanence reinforces the controversial hypothesis that geomagnetic change during a polarity reversal can be much faster than normal. The 3.9-m-thick lava (“Flow 20”) is exposed in the Sheep Creek Range (north central Nevada) and was erupted during a reverse-to-normal (R-N) geomagnetic polarity switch at 15.6 Ma. Flow 20 began to acquire a primary thermoremanence while the field was pointing east and down but was soon buried, reheated, and partially-remagnetized in a north-down direction by the 8.2-m-thick flow that succeeded it. A simple conductive cooling calculation shows that the observed remagnetization could not have occurred unless Flow 20 was still warm (about 150°C near its base) when buried and that the 53° change from east-down to north-down field occurred at an average rate of approximately 1°/week, several orders of magnitude faster than typical of secular variation.