Tiny circular plates produced by plankton and composed of CaCO3. Chalk is largely composed of coccoliths. Related Articles: Coccoliths: Tiny fossils with immense paleontological importanceFlints in the Late Cretaceous Chalk of NW EuropePalaeozoic fossils from Central Europe: A geological expedition in the Southern Alps of AustriaIssuesThree-dimensional photographs of fossils (Part 2): Stereophotography of ancient micro-organisms« Back to Glossary Index