Types of Preservations of Fossils

1. Types of Preservations of Fossils Chapter 13 – Clues to Earth’s Past

2. What will I be able to do after studying Chapter 13? • -List the condition necessary for fossils to form. • -Describe the processes of fossil formation • -explain how fossil correlation is used to determine rock age • -determine how fossils can be used to explain changes in Earth’s surface, life form and environments

3. I am a Paleontologist

4. List things that can become fossils. • Bones • Shell • Teeth • leaves • Hard parts – because they decay more slowly than soft parts do.

5. What are the conditions needed for fossils to form? • rapid and permanent burial/entombment - protecting the specimen from environmental or biological disturbance • oxygen deprivation - limiting the extent of decay and also biological activity/scavenging; continued sediment accumulation as opposed to an eroding surface - ensuring the organism remains buried in the long-term • the absence of excessive heating or compression which might otherwise destroy it.

6. Types of Preservation • Mineral Replacement • Carbon Films • Coal • Mold/Casts • Original Remains • Trace Fossils • Tracks and Burrows

7. Mineral Replacement • Bones, teeth, and skulls have spaces and these spaces can be filled with mineral deposits from groundwater. • These fossils are called per-mineralized remains. • Sometimes minerals replace hard parts such as shells and leave silica in their place.

8. Carbon Films • Carbon films are silhouettes or images like a photograph on a rock that is caused by extreme pressure and heat. • The image leaves a carbon residue or thin film showing the outline of the organism.

9. Coal • Plants in swampy areas that have died over millions of years ago are squeezed under intense pressure. • This forms coal. • These fossils are not used primarily for identification of individual plants because the plant structures have changed but are used for fuel (gas, oil, coal).

10. Molds/Casts • When hard parts of organisms fall into soft sediment, the organism gets buried in more sediment and compaction and cementation turn it into rock. • Cementation occurs when deposits of minerals from water go into the spaces between sediment particles. • With more air and water, the organism decays breaking the hard parts forming a mold. • More sediment is added and forms new rock and produces a copy or cast of the original.

11. Original Remains • Preserved animals can be found in amber. Amber is tree resin that traps insects and other small organisms. • Mammoths have been found in frozen ground and animals have been found in Tar Pits in California.

12. Trace Fossils • These are animal foot prints that can tell us how organisms lived. • They can also be images of seeds and leaves.

13. Tracks and Burrows • These are tracks made by worms or other burrowing animals. • They are not originals of the organisms but the tracks of that organism.

14. Index fossils • Remains of species that existed on Earth for relatively short periods of time Abundant and wide spread Not all rock has index fossils

15. Fossils and Ancient Environments • Help determine ancient environments • How? • Whether and area was land or covered in ocean • How deep the water was • By what kind of plants it contains – tropical