Review of paleomagnetic data from lava flows associated with the Michoacán-Guanajuato Volcanic Field: implications on the behavior of the Earth’s magnetic field during the Plio-Quaternary

Abstract

The great availability of radiometric ages for the Michoacán-Guanajuato Volcanic Field allows obtaining a detailed record of the Earth's magnetic field variations during the last 5 Ma. In this work, we analyze 112 reliable paleomagnetic directions supported by the same number of absolute ages. After discarding the transitional geomagnetic polarities, following the criterion of paleolatitudes less than 45°, the global mean paleomagnetic directions were calculated. In general terms, it is observed that the mean direction agrees, within the uncertainty interval, with the expected paleomagnetic directions obtained according to the Pliocene-Quaternary reference poles. The secular variation rate, estimated through the dispersion of the calculated virtual geomagnetic poles, and the inclination anomaly coincide with the latitudinal distribution models reported for the latitude of 20° N. An interesting finding, resulting from this compilation of paleomagnetic directions, is the possible evidence of relatively short geomagnetic events or excursions within the Matuyama and Brunhes chrones, which may help to refine the geomagnetic instability time scale. Besides, an unpublished compilation and a detailed description of more than 1000 volcanic buildings by Dr. Víctor Hugo Garduño Monroy are presented, which will undoubtedly serve as an authentic guide for paleomagnetic studies during the following decades.