Picking nannofossils: How and why

Abstract

Calcareous nannofossils are a group of micrometric fossils abundantly found in marine sediments. This group is mainly composed of coccoliths, platelets produced by the unicellular algae coccolithophores, and nannoliths whose biological affinity remains unknown. Calcareous nannofossils have a continuous record for the past 215 myr (Bown 1998) and can be found in almost every marine environment from coast to open oceans and from the Equator to the poles in surface waters (Winter et al. 1994). These microfossils are also made of low-Mg calcite (Siesser 1977; Stoll et al. 2001) which is resistant to dissolution and a common matrix for geochemical analyses in palaeoceanography. Hence, calcareous nannofossils could be one of the best fossils for palaeoceanographical studies for the last 215 myr. Their use in geochemistry is, however, less common than planktic foraminifera due to their small sizes, masses (10–1000 pg) and complex vital effects. Despite the fact that nannofossils are very small (2–20 µm), the development of high-resolution analytical devices opens up the opportunity to analyse single nannofossils or even parts of them. This is a growing field of nannofossil research. We thank the ESRF scientific committee for selecting and funding the EC-811 experiment which needed a new protocol of nannofossil separation from the matrix. We are particularly grateful to Isabelle Daniel for scientific support, Christophe Chamot at PLATIM (ENS Lyon) for methodological help and to Polymicro Technologies™ who supplied us with free capillaries during the early phase of the protocol design. We finally thank the associate editor Emanuela Mattioli and reviewers Silvia Gardin and Tom Dunkley Jones for their constructive comments on the manuscript.