FOSSILISATION -

1. The organisms are preserved and fossilized when they are buried in the ice, in an oil rich soil, in the lava of volcano, in swamps, in desiccated deserts, in rocks or under water or soil.
2. Fine mineral particles may penetrate the dead bodies.
3. Decay and disintegration of organic remains take place to leave only the harder parts, impression, moulds, casts etc.
4. The sedimented mud and sand harden with time to form rocks i.e., sedimentary rock.