Brunhes-Matuyama reversal

Geomagnetic polarities in the Upper Cenozoic . Black sections correspond to the current orientation of the earth's magnetic field, white sections to the opposite orientation.

The Brunhes-Matuyama reversal is the geomagnetic pole shift between the magnetostratigraphic chrons named after Motonori Matuyama and Bernard Brunhes around 786,000 years ago. The Brunhes-Chron continues, because since then there have only been short geomagnetic excursions , seven of which are known.

Within the Pleistocene , the Brunhes-Matuyama reversal defines the boundary between the Old Pleistocene and Middle Pleistocene .

So far, researchers have assumed that the reversal was a relatively slow development that lasted several millennia. However, according to an argon-argon dating of ash layers that closely overlap the Brunhes-Matuyama reversal in sedimentary rocks near Rome, the pole shift took place within less than 100 years. The Brunhes-Matuyama reversal is thus shorter than the Laschamp event a good 41,000 years ago, in which the pole shifts lasted 250 years and the polarity was reversed for around 440 years, but with a field strength of only up to 25% of normal Worth.

Individual evidence

1. ↑ Leonardo Sagnotti et al .: Extremely rapid directional change during Matuyama-Brunhes geomagnetic polarity reversal . Geophysical Journal International 199, 2014, pp. 1110-1124, doi : 10.1093 / gji / ggu287 .