Principle of faunal succession

The principle of faunal succession, also known as the law of faunal succession, is based on the observation that sedimentary rock strata contain fossilized flora and fauna, and that these fossils succeed each other vertically in a specific, reliable order that can be identified over wide horizontal distances.

This principle, which received its name from the English geologist William Smith, is of great importance in determining the relative age of rocks and strata.

Faunal succession was documented by Smith in England during the first decade of the 19th century, and concurrently in France by Cuvier (with the assistance of the mineralogist Alexandre Brongniart).

Archaic biological features and organisms are succeeded in the fossil record by more modern versions.

An outline microfaunal zonal scheme based on both foraminifera and ostracoda was compiled by M. B. Hart (1972).