This study is part of a project whose objective is to use groundwater geochemistry of strontium and major ions as well as isotopes of oxygen and hydrogen as geochemical tracers to help unravel the near-surface stratigraphy of the southern and northeastern Yucatan Peninsula and to determine the extent of the impact ejecta blanket mapped as the K/Pg Albion Formation where exposed. The ejecta, which crops out in a limited number of poor exposures only in the southern Yucatan Peninsula, contains abundant evaporite fragments (which contain celestite) with an Upper Cretaceous strontium isotope signature. Exposures of the poorly consolidated, clay-rich Albion Formation near the banks of the Rio Hondo, form a blanket, mantling a karstified, weathered surface formed on Cretaceous limestone. The working hypothesis of this study is that the groundwater geochemical data obtained here can serve as a tracer of the lateral extent of the Albion Formation throughout the region.