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Geomagnetic field excursion recorded 17 ka at Tianchi Volcano, China: New 40 Ar/ 39 Ar age and significance
Author(s) -
Singer Brad S.,
Jicha Brian R.,
He Huaiyu,
Zhu Rixiang
Publication year - 2014
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 - 10.1002/2014gl059439
Subject(s) - geology , excursion , lava , earth's magnetic field , volcano , paleomagnetism , geomagnetic reversal , geophysics , paleontology , magnetic field , physics , quantum mechanics , political science , law
New 40 Ar/ 39 Ar dating of a comenditic lava atop Tianchi Volcano, China, indicates eruption at 17.1 ± 0.9 ka. The flow interior records a pair of transitional virtual geomagnetic poles and a low paleointensity of ~25 μT. Thus, it records a geomagnetic field excursion that is younger than the 41 ka Laschamp or 32 ka Auckland excursions. Implications are: (1) following a repose of several tens of kyr, Tianchi Volcano became highly active immediately following termination of the last glaciation maximum. The flare‐up of silicic eruptions may reflect rapid deglaciation of the edifice. (2) A 17 ka age for the Tianchi excursion provides the first direct radioisotopic evidence that excursional behavior, which is imprecisely dated and less well documented magnetically at several other sites, is a global feature of geodynamo behavior. (3) During the Brunhes chron, 13 well‐dated excursions cluster into two periods, including seven between 17 and 212 ka, and six between about 530 and 730 ka.