For over half a century, calcite microfossils have been used to study Earth’s palaeoceanography and palaeoclimate. Coccoliths, readily fossilized calcite plates produced by a group of single-celled surface-ocean dwelling algae called coccolithophores, have composed a significant fraction of the carbonate component of pelagic sediments since the Late Triassic. However, coccoliths remain underused in palaeo-reconstructions, due largely to a lack of understanding of what controls their isotopic ...