PI and collaborators will conduct a paleontological study of the mayaroensis/eugubina Interval-Zone of Mexico. Contrary to general belief, knowledge of the planktic fauna of this zone is in its infancy. The sections to be studied contain abundant and well- preserved planktic and benthic foraminifera, as well as calcareous nannoplankton, which will allow an intergration of both fossil groups into a common biostratigraphic framework. The Mexican sections are among the most complete in the Gulf Coastal Plain of North America, and this study will help address the controversy on the nature of faunal change at the terminal Cretaceous. It will also provide the basis for further chronostratigraphic correlations within the region and globally. Furthermore, quantitative morphometrics of foraminiferal taxa will be performed in order to circumscribe the ambiguous definition of the taxa included in the "small globigerinas" group, resulting in a better understanding of their phylogenetic relationships.
