Semicontinuous paleomagnetic record of the last 1 Ma from radiometrically dated igneous rocks (Trans-Mexican Volcanic Belt and surrounding areas)

Abstract

The radiometric data available in the Trans-Mexican Volcanic Belt enables a quasi-continuous record of the Earth's magnetic field over the last million years to be obtained. Here, we analyze 149 well-defined paleomagnetic directions supported by an equal number of isotope ages. Eleven new paleomagnetic directions from the Tacambaro-Puruaran area (the Michoacán Guanajuato Volcanic Field) are incorporated into the database. Global mean paleomagnetic directions are calculated for one Ma after discarding transitional lavas. The mean direction agrees with the expected paleomagnetic directions obtained from the Pliocene-Quaternary reference poles within the range of uncertainty. The secular variation rate estimated through the scattering of the calculated virtual geomagnetic poles, and the inclination anomaly, both agree with recently reported latitudinal distribution models. An interesting feature of the paleomagnetic direction compilation is the possible evidence of relatively short geomagnetic events or excursions within Matuyama and Brunhes chrons, which may help to refine the geomagnetic instability time scale (GITS).