Deep-sea benthic foraminiferal response to the early Oligocene cooling: a study from the Southern Ocean ODP Hole 1138A.

Ongoing rapid climate change has a major effect on marine fauna, and understanding these faunal changes analogous to future climatic periods is crucial. The Oligocene is commonly considered a critical transition period, linking the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene. Here, we show the response of marine benthic foraminifera to the early Oligocene climatic changes at Ocean Drilling Program (ODP) Hole 1138A of the Southern Ocean (Indian Sector). We made use of the diversity parameters, the relative abundance of dominant benthic foraminifera, and isotopic data to understand past oceanographic changes. Our results suggest that the early Oligocene was an interval of unstable conditions dominated by the species of high oxygen, intermediate food supply, and well-ventilated, cold, corrosive bottom water conditions. The species richness abruptly decreases at the end of the studied interval, which shows the major Southern Hemisphere glaciation. During this time, species were characterized by relatively cold and carbonate-corrosive bottom water. Additionally, the present study of the benthic foraminiferal abundance and diversity indices reveals the cooling of the Southern Ocean at the early and late stages of the studied interval interrupted by a short-lived warming event. The study further enhances the understanding of paleo-marine ecology by evaluating the response of deep-sea benthic foraminifera to global climate change. [ABSTRACT FROM AUTHOR]