The following is a list of
geomagnetic reversal
A geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged (not to be confused with geographic north and geographic south). The Earth's field has alternated ...
s, showing the ages of the beginning and end of each period of normal polarity (where the polarity matches the current direction).
Source for the last 83 million years: Cande and Kent, 1995.
[Cande, S.C., and D.V. Kent, Revised calibration of the geomagnetic polarity timescale for the late Cretaceous and Cenozoic, J. Geophys. Res., 100, 6,093-6,095, 1995.]
Ages are in million years before present (''mya'').
References
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Geochronology
Paleomagnetism
Geomagnetic reversal