Upper Cretaceous and lower Paleogene benthic Foraminifera from northeastern Mexico

Abstract

The deep-sea, Upper Cretaceous through Paleocene benthic Foraminifera from the Mendez and Velasco Formation (Tampico Embayment, northeastern Mexico) were first described in classical papers of the 1920s. These faunas were among the first deep-water faunas of this age to be described, and many of the species have been recognized in Deep Sea Drilling Project and Ocean Drilling Program sites worldwide. We present the first taxonomic update of these classic faunas since the 1920s, with special attention to species first described from this area, and species that have been widely used in paleobathymetric reconstructions. Benthic foraminiferal assemblages were analyzed from the Cretaceous Mendez and Paleocene Velasco Formations in seven sections in the northeastern and central-eastern parts of Mexico. The Foraminifera are generally well preserved, although commonly recrystallized and filled with sparry calcite. They indicate paleodepths ranging from upper to middle bathyal for the three northernmost sections, and lower bathyal for the other sections. The clastic unit between the Mendez and Velasco Formations contains a mixture of neritic and bathyal species, and probably originated as a result of mass-wasting associated with the bolide impact on the Yucatan peninsula. From the about 140 benthic foraminiferal taxa identified, we describe 88 species belonging to 41 genera. These correspond to the most representative taxa in northeastern Mexico across the Cretaceous-Paleogene transition, because of their common occurrence, paleobathymetric significance, or first description from this region.