Brunhes–Matuyama reversal

Template:Short description The Brunhes–Matuyama reversal, named after Bernard Brunhes and Motonori Matuyama, was a geologic event, approximately 781,000 years ago, when the Earth's magnetic field last underwent reversal.<ref>Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Estimations vary as to the abruptness of the reversal. A 2004 paper estimated that it took over several thousand years;<ref name="slow">Template:Cite journal</ref> a 2010 paper estimated that it occurred more quickly,<ref name="SN090210">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> perhaps within a human lifetime;<ref>Template:Cite journal</ref> a 2019 paper estimated that the reversal lasted 22,000 years.<ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The apparent duration at any particular location can vary by an order of magnitude, depending on geomagnetic latitude and local effects of non-dipole components of the Earth's field during the transition.<ref name="slow" />

The Brunhes–Matuyama reversal is a marker for the Global Boundary Stratotype Section and Point (GSSP) defining the base of the Chibanian Stage and Middle Pleistocene Subseries at the Chiba section, Japan, which was officially ratified in 2020 by the International Union of Geological Sciences.<ref name="GSSP Web">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Head2021">Template:Cite journal</ref> It is useful in dating ocean sediment cores and subaerially erupted volcanics.

There is a highly speculative theory that connects this reversal event to the large Australasian strewnfield (c. 790,000 years ago),<ref name="Glass">Glass, B. P., Swincki, M. B., & Zwart, P. A. (1979). "Australasian, Ivory Coast and North American tektite strewnfields – Size, mass and correlation with geomagnetic reversals and other earth events" Lunar and Planetary Science Conference, 10th, Houston, Tex., March 19–23, 1979, pp. 2535–2545.</ref> although the causes of the two are almost certainly unconnected and only coincidentally happened around the same time.Template:Citation Needed Adding to the data is the large African Bosumtwi impact event (c. 1.07 million years ago) and the later Jaramillo reversal (c. 1 million years ago), another pair of events which has not gone unnoticed.<ref name="Glass" />

See also

• Bosumtwi impact event
• Gauss–Matuyama reversal
• Geomagnetic reversal
• Jaramillo reversal
• List of geomagnetic reversals

Further reading

• Behrendt, J.C., Finn, C., Morse, L., Blankenship, D.D. "One hundred negative magnetic anomalies over the West Antarctic Ice Sheet (WAIS), in particular Mt. Resnik, a subaerially erupted volcanic peak, indicate eruption through at least one field reversal" University of Colorado, U.S. Geological Survey, University of Texas. (U.S. Geological Survey and The National Academies); USGS OF-2007-1047, Extended Abstract 030. 2007.