Stable carbon and oxygen isotope ratios of foraminifera from the latest Miocene to earliest Pliocene of Ceare Rise, western tropical Atlantic

Menardellids are widely distributed in tropical to subtropical waters from Miocene to modern time, revealing a stable isotopic signature characteristic for the top of the thermocline and shallower rather than deeper habitat depth. Menardellid response to its environment reveals a tripartite pattern.

The first interval from ~6.34 to 5.75 Ma is marked by a dominance of Menardella limbata, frequent changes in coiling direction, and variable abundance with strongest reductions during intervals of dextral dominance. The onset of an interval of cooling and ice build-up at 5.82 Ma coincides with a weakening of the mixed layer leading to nearly 70 kyr of strongly reduced menardellid abundance. At 5.75 Ma, Menardella multicamerata replaces M. limbata as the prevailing menardellid species, at the same time as the overall abundance of menardellids stabilises.