Significant changes of the chemistry, temperatures, and plankton fertility in the oceans took place in the first fifty thousand years of the Tertiary. Those changes are recorded by the bulk chemical, the oxygen-isotope, and the carbon-isotope compositions of the oldest Tertiary sediments. Detailed analyses of a Cretaceous/Tertiary section from a South Atlantic drillsite indicated that the extinction of the Cretaceous nannoplankton species took place during the times of the environmental changes. Taking into consideration the various evidences for a terminal Cretaceous large-body impact, we proposed that the impact event was the cause of the changes in ocean environments, which in...