Volume and carbonate production estimates of early Palaeogene calcareous nannofossils

To assess the role played in the carbonate budget by calcifying phytoplanktonic organisms, it is necessary to provide reliable quantitative estimates of the calcite secreted by calcareous nannoplankton, which certainly have ad a vital role in the global carbon cycle since the Jurassic by supplying organic carbon and calcium carbonate to the deep ocean. Reconstructed volume/mass estimates of early Palaeogene calcareous nannofossils based on previous methodologies/techniques applied to extant nannoplankton and/or fossil assemblages suggest that carbonate produced by specific taxa significantly varies both in time and in space. Changes in the calcite within a single taxon and all the more so in the calcium carbonate produced by the entire assemblage are influenced by modifications of palaeoenvironmental conditions and are used as palaeoecological and/or palaeo-oceanographic proxy.