Late Ediacaran Hyperactivity Period: Quantifying the Reversal Frequency

—The previous paleomagnetic studies of the Upper Vendian Zigan Formation sediments on the western slope of Southern Ural revealed uncommonly numerous magnetic polarity zones (Bazhenov et al., 2016). The dating of magmatic zircons from the tuff interlayer constrained the age of this formation to 547....

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Published in:Izvestiya. Physics of the solid earth 2021-03, Vol.57 (2), p.247-256
Main Authors: Levashova, N. M., Golovanova, I. V., Rud’ko, D. V., Danukalov, K. N., Rud’ko, S. V., Sal’manova, R. Yu, Sergeeva, N. D.
Format: Article
Language:English
Subjects:
Earth and Environmental Science
Earth Sciences
Geomagnetism
Geophysics/Geodesy
Interlayers
Palaeomagnetism
Paleomagnetic studies
Paleomagnetism
Phanerozoic
Sediments
Tuff
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Summary:—The previous paleomagnetic studies of the Upper Vendian Zigan Formation sediments on the western slope of Southern Ural revealed uncommonly numerous magnetic polarity zones (Bazhenov et al., 2016). The dating of magmatic zircons from the tuff interlayer constrained the age of this formation to 547.6 ± 3.8 Ma. The rate of reversals estimated from most general considerations is about 20–30 per Myr which is approximately two to three times higher than the highest reversal frequency in Phanerozoic. In this work, a more accurate estimate of the rate of reversals is obtained from cyclostratigraphic study of the lower red-rock part (74 m) of the Zigan Formation in its continuous section along the Sterlitamak–Magnitogorsk road—the longest one among those previously studied by the paleomagnetic method. The correlation of the detailed cyclostratigraphic studies with the magnetostratigraphic column allowed a more reliable estimation of the reversal rate. The studied section in which we identified 20 reversals was accumulated during 1.6 Myr, i.e., the reversal frequency in this interval was 12–13 per Myr. Our quantitative assessment shows that the previous studies overestimated the geomagnetic reversal frequency by a factor of two. However, even the reversal rate estimated in this study can be regarded anomalously high, and the previous conclusions about the existence of a period with anomalously frequent reversals in terminal Ediacaran 547.6 ± 3.8 Myr ago can be considered validated.
ISSN:1069-3513
1555-6506
DOI:10.1134/S1069351321020026