From Dinosaur to Fossil

Article | Updated 10 years ago

Bacteria are part of the fossilisation process, turning dinosaur bones into stone.

Cretaceous dinosaur fossils are mainly found in areas that were flood plains during this time. Dinosaurs often drowned and were buried under the sand and mud (sediment) that spread over the flat landscape during flooding. Once buried, bacteria feeding on the decaying bones changed the chemistry in the surrounding sediment. This caused minerals in the ground water to form crystals within the bones, slowly turning them to stone. Over time, the weight of sediments spread over the flood plain caused it to sink and new layers of sediment to build up over the fossilised bones.

Turning dinosaur bones into stone

Radioactive dinosaurs

In some sedimentary rocks, uranium in the ground water can form crystals in the spaces within dinosaur bones, making them radioactive. The Morrison Formation in the USA from the Late Jurassic is well known for its radioactive dinosaur bones.

This Late Jurassic dinosaur bone has been mineralised with the yellowish, radioactive uranium mineral called carnotite

Yellow bones
This Late Jurassic dinosaur bone has been mineralised with the yellowish, radioactive uranium mineral called carnotite.
IMAGE: JAMES ST JOHN