Fossils

Defining Fossils

• Fossils are the preserved remains, traces or imprints of organisms from the past that existed and lived in geological times prior to humans.
• There are several types of fossils including body fossils - the physical remains of an organism; and trace fossils - tracks, trails and burrows that indicate the organism’s behaviour.

Formation of Fossils

• The process of fossilisation begins when an organism dies, and its remains are quickly buried by sediment.
• Over time, the sediment encasing the organism hardens into rock and the organic material of the organism is replaced by minerals in a process known as mineralisation.
• Ideal conditions for fossilisation include rapid burial (to prevent scavenging and decomposition) and low oxygen environments (to slow decay).

Key Features of Fossils

• Fossils often show the physical structure of the organism they come from, but the level of detail preserved varies greatly.
• Some fossils can show signs of soft tissue preservation where soft parts of the organism (such as skin or feathers) become mineralised.
• Fossils can also demonstrate trace fossils, which provide clues about the behaviour of the organism - for instance, tracks can indicate the speed and direction of movement.

Interpreting Fossils

• The study of fossils, known as palaeontology, can tell us about life in geological time periods.
• Fossils provide valuable insights into evolutionary patterns, species diversity, climate changes and shifts in the Earth’s tectonic plates.
• Certain fossils, known as index fossils, are particularly useful in dating and correlating the age of rocks. These are fossils of a species that existed through a narrow time range but were geographically widespread.

Fossils and the Rock Cycle

• Fossils are most commonly found in sedimentary rocks (like limestone and sandstone) due to their deposition in water and subsequent burial.
• While more rare, fossils can also be found in metamorphic rocks if the rock hasn’t been subjected to extreme heat and pressure.

Economic Importance of Fossils

• Fossils like coal, oil and gas, derived from the remains of plants and animals, are used as energy sources.
• Some fossils (like ammonites and fossilised wood) are widely collected, sold, and traded and have become part of the global gem and jewellery market.
• Most importantly, the study of fossils has significant implications for understanding climate change and biodiversity, informing present-day environmental conservation efforts.