@Article{Schmitt3:2010, author = {A.K. Schmitt and D.F. Stockli and S. Niedermann and O.M. Lovera and B.P. Hausback}, title = {Eruption ages of Las Tres V\'{i}rgenes volcano (Baja California): A tale of two helium isotopes}, journal = {Quat. Geochronol.}, booktitle = {}, editor = {}, publisher = {}, month = {}, year = {2010}, volume = {5}, number = {}, pages = {503--511}, note = {}, annote = {}, keywords = {}, url = {http://sims.ess.ucla.edu/pdf/Schmitt3_et_al_2010.pdf}, doi = {10.1016/j.quageo.2010.02.004}, isbn = {}, abstract = {La Virgen tephra is the product of the youngest and most voluminous explosive eruption of Las Tres V\'{i}rgenes volcano (Baja California). Combined U-Th and (U-Th)/He zircon dating allows accurate correction for uranium-series disequilibrium, and yields an eruption age for La Virgen tephra of View the MathML source (2$\sigma$). No difference in eruption ages was found between samples from proximal and distal La Virgen tephra. A previously undated tephra south of Las Tres V\'{i}rgenes volcano yielded U-Th and (U-Th)/He zircon ages overlapping those of La Virgen tephra, which suggests that both units are identical. $^{3}$He surface exposure ages (T$^{3}$) of overlying mafic lavas are 25.5 $\pm$ 4.4 and 22.0 $\pm$ 2.5 ka, and agree within uncertainties with $^{21}$Ne exposure ages (T$^{21}$). T$^{3}$ and T21 ages for dome lava south of La Virgen are slightly older (T$^{3}$ = 42.5 $\pm$ 3.8 ka). (U-Th)/He and surface exposure ages are stratigraphically consistent, whereas a published Holocene $^{14}$C charcoal age from the distal site could not be confirmed. Instead, abundant zircon crystals with (U-Th)/He ages between 1 and 22 Ma are interpreted as undegassed detrital grains, suggesting reworking of pumice at the distal location. The results presented here underscore the potential of combined U-Th and (U-Th)/He zircon dating for Quaternary tephrochronology.}