238U‐230Th dating of a geomagnetic excursion in Quaternary basalts of the Albuquerque Volcanoes Field, New Mexico (USA)

Abstract

We report the 238U‐230Th age derived from samples from three basalt flows from the Albuquerque Volcanoes Field, central New Mexico (USA), interpreted to have erupted during one of the Bruhnes Chron geomagnetic field polarity events. Whole‐rock samples and magnetite separates from two of the samples define an isochron with an age of 156±29 ka (2σ). It is now possible to determine the ages of geomagnetic excursions with reasonable precision, by the 238U‐230Th method, using basalts erupted between possibly 25 and up to 250 ka. Although a strict correlation of the polarity event recorded by the Albuquerque lavas with other high amplitude field phenomena in the latest Quaternary is not yet possible, the Blake and the less well‐documented Old Crow and Biwa I/Jamaica events are likely candidates.