Calcareous nannofossils

Calcareous nannofossils are very small, tiny pieces of stone less than 30 microns across. They are a type of microfossil similar to coccoliths, which are made by modern-day coccolithophores. These tiny fossils are very useful for learning about Earth's history because they change quickly over time and are found in many places.

Because nannofossils are so common and change fast, scientists can use them to figure out how old different layers of rock are. This helps in studying the history of life and Earth’s climate. Their importance grew a lot after deepwater drilling began in 1968 with the Deep Sea Drilling Project, and they have been studied a great deal since then. Nannofossils give us one of the most complete records of life from the past, stretching back 220 million years.

History of research

Christian Gottfried Ehrenberg looked at chalk from Ruegen in 1836 and saw tiny round discs, which we now call coccoliths. He drew these discs and Discoasters in his book in 1854, but he thought they were just natural rock shapes. In 1858, T. H. Huxley named these discs "coccoliths" because of their shape, still thinking they were not made by living things. But in 1861, George Charles Wallich and Henry Clifton Sorby saw that these discs were actually parts of very small living things, called coccospheres. Huxley then changed his mind and said they were the armor of tiny unknown organisms, named Bathybius haeckelii. Scientists on the Challenger expedition later found out that these discs were really the protective covering of very small plants called nannoplankton algae (a term created in 1909).

In the early 1900s, scientists studied these tiny plants, which helped researchers use them to figure out the age of rocks in 1954. The Deep Sea Drilling Project in 1968 showed how useful these tiny fossils could be. Scientists began using special microscopes in the 1950s and 1960s to study them even better.

Terminology

Over time, scientists have used different words to talk about these tiny fossils. They are sometimes called "nannoplankton" or "coccoliths". The name "calcareous nannofossil" became popular in the early 1970s, especially in reports from the Deep Sea Drilling Project. The word "calcareous" comes from a Latin word meaning "containing lime".

Different scientists may use these words in slightly different ways. Some use "coccolith" only for round shapes, like those made by living coccolithophores, and use "nanolith" for other shapes. Others use "coccolith" for all shapes. Some scientists use "nannoplankton" for the living organisms and "nannofossils" for those that are no longer alive, while others use "nannoplankton" for both.

Biostratigraphy

Calcareous nannofossils are very helpful for studying the history of Earth. They have many useful features:

• They have been around for 220 million years, from long ago until today.
• They are found a lot in ocean sediments.
• They are found all over the world because they float in the water.
• They change quickly, creating many points to mark when new types appeared or old types disappeared.
• They are so small that scientists can study them even with tiny samples.

These tiny fossils help scientists understand layers of Earth’s history. They are especially useful for marking important changes in layers from the time of the dinosaurs to today. Different scientists have created ways to organize these layers, using special codes to keep track.

Other uses

Calcareous nannofossils help scientists in archaeology to learn where different old objects come from. These objects include ceramics, small square pieces called tesserae, the backgrounds of paintings, statues, and building stones. By studying these tiny fossils, researchers can discover more about the history and origins of these artefacts.