This interpretation was challenged by Renne et al. (2005) based on Ar/Ar dates on the basaltic lapilli retrieved from the tuff, with a mean age of 1.30 + 0.03 Ma. Renne et al. (2005) also presented paleomagnetic evidence, with reverse paleomagnetic directions for the Xalnene tuff, which were correlated to the Matuyama C1r.2r chron. González et al. (2006a, b) argued
that the lapilli in the tuff could be reworked or inherited, resulting in heterogeneous material not suitable for dating