From volume estimates to carbonate production of Late Paleocene - Early Eocene calcareous nannofossil assemblages: a first step to reconstruct absolute abundances of calcareous nannoplankton

Stable carbon and oxygen isotope compilations available from the literature point out that the variations observed in the marine sediments deposited between 60 and 50 Ma are the most prominent of the entire Cenozoic. So far, our knowledge of early Paleogene depicts an articulated and complex evolution, which can be roughly described as a long term global warming trend interrupted by several hyperthermal events. In this paleoclimatic context, we are interested to reconstruct changes occurred in one of the major component of the past (modern) sea surface oceans: the calcareous nannoplancton. Paleoecological interpretations have been proposed based on classical palecological approaches, we instead indicate an alternative/auxiliary methodology which essentially consists of an estimate of carbonate flux of calcareous nannofossil assemblages. In order to assess the role played in the carbonate budget by calcifying phytoplanktonic organisms, as carbonate producers, it is necessary to provide reliable estimates of the calcite secreted by calcareous nannoplankton, which certainly have had a vital role in the global carbon cycle since the Mesozoic Era by supplying organic carbon and calcium carbonate to the deep ocean.