Geomagnetic reversal
The Kiaman Reverse Superchron lasted from the late Carboniferous to the late Permian. That is more than 50million years, from 312 to 262 million years ago (mya). The magnetic field had reversed polarity. The name "Kiaman" derives from the Australian village of Kiama, where some of the first geological evidence of the superchron was found in 1925.