2. TYPES OF PRESERVATIONS OF FOSSILS Chapter 13 – Clues to Earth’s Past

3. 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

4. I am a Paleontologist

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

6. 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.

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

8. 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.

9. 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.

10. 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).

11. 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.

12. 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.

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

14. 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.

15. 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

16. 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