Abstract The Cretaceous-Paleocene boundary on the Campeche Shelf is established with plank-tonic foraminiferal biostratigraphy from core and chip samples and is correlated with gamma-ray well logs. The Campanian-Maestrichtian Cantarell Formation is herein formally described as a breccia formed of calcareous or dolomitized fragments cemented by micrite. Its age is established using Globotruncana species. The Abkatun Formation is formally described as brown shale and shaly limestone that contains Parvularugoglobigerina trinidadensis and Pa. pseudobulloides of the lower Paleocene. The upper Paleocene is represented by greenish-gray shale that contains Morozovella velascoensis, M. formosa formosa, M. aragonensis , and Globoanomalina pseudomenardii. The broad regional distribution and distinctive lithology of the Cantarell and Abkatun Formations allow them to be differentiated from overlying and underlying formations. The boundary between the lower and upper Paleocene is conformable.