Calcareous nannofossils

Calcareous nannofossils are a class of tiny (less than 30 microns in diameter) microfossils that are similar to coccoliths deposited by the modern-day coccolithophores. The nannofossils are a convenient source of geochronological data due to the abundance and rapid evolution of the single-cell organisms forming them (nannoplankton) and ease of handling of the sediment samples. The practical applications of calcareous nannofossils in the areas of biostratigraphy and paleoecology became clear once the deepwater drilling took off in 1968 with the Deep Sea Drilling Project, and they have been extensively studied ever since. Nannofossils provide one of the most important paleontological records with the contiguous length of 220 million years.