The fossilised remains of a 40 million-year-old diatom species Stephanopyxis grunowii from a diatomite in Oamaru, New Zealand.
Credit: Anatoly Mikhaltsov
Rare and buried deep inside the earth for thousands of years, fossils inspire awe and tell a tale frozen in time. Although visible to the naked eye, dinosaur, whale, mammoth or human fossils are scant and hard to find. On the other hand, microfossils—tiny remains of bacteria, diatoms or protists—are ubiquitous on every continent and ocean. The oldest record of life on Earth, discovered in the hydrothermal vent precipitates off the Canadian coast in 2017, are 4.28 billion years old microfossils.
Microfossils range between a few microns to a couple of millimetres in size, but they paint a picture of how our planet looked billions of years ago. Using them, scientists can decipher what gases were present in our atmosphere billions of years ago, how hot the planet was or how cold the oceans were. As oil and natural gas are fossil juices, scientists use microfossils as reliable indicators of large fossil-fuel deposits. Since most life forms live in the oceans, most microfossils are found in the sediments of the world’s oceans.
Unlike dinosaurs or humans, bacteria and diatoms don’t have skeletons. Their fossils result from the mineralization of silicates, calcium carbonates and phosphates, which become a part of sedimentary rocks. For example, when diatoms fossilize, the silicates in their outer shell form frustules. Diatomites—soft, light grey or white-coloured rocks formed by billions of frustules—are mined to obtain fine abrasives used to filter water, make cosmetics and toothpaste, or as diatomaceous earth. The sedimentary rocks used to build Egyptian pyramids contain shells of foraminifera—the most abundant form of microfossils.
Scientists have reported finding microfossils in the Himalayas, the Vindhyas, the Deccan plateau and other parts of India. Although the field was first recognized in 1883 as a subdivision of palaeontology, interest in the study of microfossils has resurged as we decipher what the planet's future looks like with climate change and how organisms could adapt to our heating planet.
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