Fossilised

Fossilised is the British English spelling of fossilized, an adjective used to describe organic materials or structures that have been preserved through fossilisation. In general, a fossil is the remains or traces of ancient life that have persisted long enough to be studied by scientists. The American variant fossilized is also common in global usage.

Fossilisation occurs through several pathways. Permineralization or petrification fills pores with minerals, turning tissue into stone. Replacement dissolves the original material and deposits minerals molecule by molecule. Carbonization leaves a thin carbon film of the organic material. Casts and molds capture the external form, while remains preserved in amber, tar, ice, or anoxic sediments can achieve exceptional preservation.

Fossils fall into body fossils, which preserve parts of organisms such as bones, teeth, shells, or wood, and trace fossils, which record activities such as footprints, burrows, or coprolites. Preservation is biased toward hard parts and conditions that slow decay, such as rapid burial, low oxygen, and mineral-rich waters, so the fossil record is incomplete and focused on certain environments.

Fossils help determine the age of rocks through relative dating methods and, when paired with radiometric dating of surrounding material, can constrain numerical ages. They also inform about past environments, climates, and biological evolution. The study of fossils, paleontology, relies on careful strata description, comparative anatomy, and, increasingly, imaging and molecular techniques.