Sr/Ca ratios of coccoliths from the Paleocene-Eocene Thermal Maximum

The response of the planktic ecosystems and productivity to the dramatic climate changes of the PETM may represent a significant feedback to the carbon cycle changes, but has been difficult to document. We examine Sr/Ca ratios in calcareous nannofossils in sediments spanning the PETM in three open ocean sites as a new approach to examine productivity and ecological shifts in calcifying plankton.

The large heterogeneity in Sr/Ca among different nannofossil genera indicates that nannofossil Sr/Ca reflects primary productivity-driven geochemical signals and not diagenetic overprinting. Elevated Sr/Ca ratios in several genera and constant ratios in other genera suggest increased overall productivity in the Atlantic sector of the Southern Ocean during the PETM. Dominant nannofossil genera in tropical Atlantic and Pacific sites show Sr/Ca variations during the PETM which are comparable to background variability prior to the PETM.