Keller et al. recently suggested (1) that there are several middle Eocene to middle Oligocene microtektite horizons and implied that these horizons indicate separate tektite events. Although there is no a priori reason why there could not be multiple tektite events during this period, Keller et al. do not provide any descriptive, petrographic, or compositional data to support their identification of microtektites from previously unreported stratigraphic layers. Furthermore, the lack of data on abundance versus depth and of compositional data does not allow the reader to decide if the microtektite occurrences are due to several events, as Keller et al. claim, or merely to one event with scattered younger occurrences attributable to reworking.  PDF