Coccoliths

Calcareous nannofossils (coccoliths) are among the tiniest fossils preserved in the sedimentary record, measuring around 5 to 10 microns. The image (plate) shows petrographic microscope photos of some of the most characteristic coccoliths of the Cretaceous/Paleogene (K/Pg) boundary. This boundary is associated with one of the most studied mass extinctions in the geological record, which has been correlated to a major catastrophic event. Photos 1 to 4 show nannofossils of the Upper Cretaceous (Maastrichtian) that are thought to have gone extinct at the K-Pg catastrophic event. Photos 5 to 7 are of Cretaceous survivors that show continuous distribution into the Paleogene (Danian). These last species are considered adapted to cold water and eutrophic environments (r-selected taxa). Photos 8 and 9 show Paleogene taxa, not present below the boundary. (Photos by E. Belia)

microfossils K-Pg boundary extinction Cretaceous Paleogene Maastrichtian Danian coccoliths nannoplankton Fossil Kinds and Sites