Microfossils

Microfossils are fossilized remains or traces of tiny organisms, typically less than about one millimeter in size, preserved in sedimentary rocks and soils. Because of their small size and often rapid evolution, microfossils provide detailed records of past life and environments, and they are widely distributed in marine and freshwater deposits as well as in some terrestrial sediments. They may be preserved as calcareous or siliceous shells, tests, or impression structures, and sometimes as organic residues.

The major groups commonly recovered as microfossils include foraminifera, radiolarians, diatoms, coccolithophores, and ostracods, as well as conodont elements from extinct early vertebrates and calcareous nanofossils such as coccoliths. Foraminifera form calcium carbonate tests and are abundant in marine settings, radiolarians and diatoms possess silica skeletons, coccolithophores produce intricate calcium carbonate plates, ostracods are small crustaceans with calcite shells, and conodonts are microfossil tooth-like elements. These groups span a range of ecological niches and environmental settings, contributing complementary information about past oceans, climates, and ecosystems.

Methods for studying microfossils involve sampling and preparation of sediments, disaggregation, and separation of microfossils from matrix, often using acid digestion for carbonate-rich rocks or heavy-liquid and filtration techniques. Specimens are examined under light microscopy and, where needed, scanned with electron microscopy. Identification relies on reference collections and systematic keys. Data derived from microfossils support biostratigraphy, dating of rock sequences, and reconstruction of paleoenvironmental conditions, including past temperatures, salinities, and productivity.

Limitations include preservation biases that favor certain mineralogies, dissolution or recrystallization in some settings, and taxonomic challenges in distinguishing closely related forms. Despite these constraints, microfossils remain essential tools in geology, paleontology, and climate studies.