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Very rapid geomagnetic field change recorded by the partial remagnetization of a lava flow
Author(s) -
Bogue Scott W.,
Glen Jonathan M. G.
Publication year - 2010
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2010gl044286
Subject(s) - lava , paleomagnetism , earth's magnetic field , geology , polarity (international relations) , remanence , geomagnetic pole , flow (mathematics) , secular variation , geophysics , magnitude (astronomy) , geodesy , paleontology , volcano , magnetic field , physics , mechanics , magnetization , astrophysics , quantum mechanics , genetics , biology , cell
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.