Sedimentology and micropaleontology (benthic foraminifera) of the Cretaceous-Tertiary transition: Correlation between the Gulf of Mexico and the Tethys area (Spanish text)

The sedimentological and micropaleontological study of several Cretaceous-Tertiary sections has contributed to a more detailed knowledge of this moment of the Earth's history, which is characterized by the extinction of numerous organisms and the sedimentation of anomalous deposits.; In the Gulf of Mexico area, the Cretaceous/Tertiary (K/T) boundary is located at the base of a Clastic Unit, variable in thickness and deposited under turbiditic currents. These currents have been related to the seismic instability triggered by a meteoritic impact occurred at Chicxulub (Yucatán) in coincidence with the K/T boundary. Impact evidences are less evident in the Tethys area, where the K/T boundary is located under a decimetric layer of dark clays that contain a red layer with geochemical and mineralogical anomalies toward its base. The study of benthic foraminifera allowed us to infer the paleobathymetry of all sections, as well as to document the allochtony of the Clastic Unit in the Gulf of Mexico.; Whereas benthic foraminifera suggest environmental stability during the Maastrichtian, important changes in the communities were recorded in coincidence with the K/T boundary, indicating a drastic drop in primary productivity. The benthic response has been related to the web-chain collapse, and to the progressive recovery of the productivity through the basal Danian.; Sedimentological and micropaleontological evidences are compatible with the theory of a meteoritic impact occurred at the K/T boundary, that led to an anomalous sedimentation and globally triggered paleoenvironmental and biological processes.