Revaluation of geomagnetic excursions recorded in lava flows from the Ceboruco and Tequila volcanic fields, trans-mexican volcanic belt

摘要

Detailed records of the Earth's magnetic field have shown that it has occasionally reversed its polarity. Several cases have also been found when the Earth Magnetic Field has significantly deviated for a relatively short time from its usual position defining a geomagnetic excursion, a kind of aborted reversal. Although many transitional paleodirections were revealed during the last decade in Central Mexico, their reliability was questioned. Recent paleomagnetic studies along the Trans-Mexican Volcanic Belt report contradictory results on the evidence of intermediary geomagnetic regimes. This work provides new paleomagnetic data which, combined with the information already reported, evaluate the fidelity of such events registered in the lava flows associated to the Tequila and Ceboruco Volcanic Fields. This critical reassessment allowed to discard the evidence of the Levantine geomagnetic excursion (362 +/- 13 kA) but strongly confirms the occurrence of the Big Lost event (592 +/- 20 ka). These findings represent an important contribution to the geomagnetic instability time scale for the last 1 Ma.