WAXING AND WANING OF PLANKTONIC FORAMINIFERAL DIVERSITY IN THE OLIGOCENE ICEHOUSE (Invited Presentation)

Decades of past research from multiple authors have produced a comprehensive database of the emergence and extinction of all documented Paleogene planktonic macroperforate foraminifera. It is well established that major turnover of planktonic foraminifera occurred at the Eocene Oligocene Transition (EOT) (~34-33.5 Ma), but what happened next? We compiled evolution and extinction data across a time period spanning the middle Eocene to early Miocene (40 to 23 Ma). Our dataset constrains the stratigraphic range of 129 species, divided into 24 time bins of 500,000 years’ duration. Here we show that the diversity crisis in planktonic foraminifera extended a further 2 million years into the Oligocene. We deconstruct the intrinsic and extrinsic forces which produce the patterns observed during this interval of significant climatic transition and taxonomic turnover. The turnover impacted each niche (ecogroup) disproportionately, thermocline species were unaffected and diversity remained the same from 40 to 23 Ma. The proliferation of diversity in the latest Oligocene is caused by an extended interval of low extinction, coupled with an increase in origination. We compare our new diversity records to climate proxies of surface water and deep sea temperatures and carbon burial. The E/O boundary extinction was triggered by temperature decline, but further diversity loss and subsequent recovery are unrelated to temperature change.