Calcareous nannofossils

Calcareous nannofossils are very small pieces of stone, smaller than 30 microns. They are like tiny fossils, similar to things made by modern coccolithophores. These little fossils help us learn about Earth's past because they change quickly and are found almost everywhere.

Because nannofossils are common and change fast, scientists use them to find out how old rocks are. This helps us study how life and Earth’s climate have changed. They became very important after deepwater drilling started in 1968 with the Deep Sea Drilling Project. Since then, scientists have studied them a lot. Nannofossils give us a detailed record of life from long ago, going 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 discovered 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.

In the early 1900s, scientists studied these tiny plants. This helped researchers 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

Scientists have used many names for these tiny fossils. Sometimes they are called "nannoplankton" or "coccoliths". The term "calcareous nannofossil" became popular in the 1970s, especially in reports from the Deep Sea Drilling Project. The word "calcareous" means "containing lime" in Latin.

Different scientists may use these words in 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 help us learn about Earth's history. They are useful because:

• They have existed for 220 million years, from long ago until now.
• They are often found in ocean sediments.
• They are found everywhere because they float in the water.
• They change quickly, which creates many points to mark when new types appeared or old types disappeared.
• They are so small that scientists can study them even with very small 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 made ways to organize these layers, using special codes to keep track.

Other uses

Calcareous nannofossils help scientists in archaeology learn where 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.