Evidence and causes of the main extinction events in the Paleogene based on extinction and survival patterns of foraminifera

We review the four main extinction events in the Paleogene, from the Cretaceous/Paleogene boundary to the Eocene/Oligocene boundary, integrating the results obtained from a study of foraminiferal assemblages with other paleontological and geological data. Different survival strategies followed by the species are described and the duration of the phases of extinction, survival, and recovery is estimated. The models and patterns of extinction of the foraminifera are highlighted. We present a range of evidence and paleo-environmental factors and analyze the possible causes of extinction. A new terminology for mass extinction events is proposed: sudden mass extinction would have happened virtually instantaneously and the process would have taken a few years or decades (Cretaceous/Paleogene boundary). Rapid mass extinction is defined as that which occurred in relatively short events, around 100 kyr (Paleocene/Eocene and Eocene/Oligocene boundaries). Slow mass extinctions are suggested to have lasted around 1 Myr (Bartonian/Priabonian transition) and may even have lasted for several million years.