II. What are Fossils?

Fossils are the remains or traces of prehistoric life. They are important components of

sediment and sedimentary rocks.

The type of fossil that is formed is determined by the conditions under which an organism died

and how it was buried.

II. Altered vs. Unaltered Remains

A. Unaltered Remains

Some remains of organisms—such as teeth, bones, and

shells—may not have been altered, or may have changed

hardly at all over time.

B. Altered Remains

• The remains of an organism are likely to be changed over time.

• Fossils often become petrified or turned to stone.

• Molds and casts are another common type of fossil.

• Carbonization is particularly effective in preserving leaves and delicate animals. It occurs when an organism is buried under fine sediment.

a. Trace fossils are indirect evidence of prehistoric life.

Can tell us about the activity, habitat, diet, etc. of an animal

Examples: Tracks, shelters, and poop

III. Indirect evidence

Not the ACTUAL Fossil!

IV. Preserved Fossil Types

Conditions Favoring Preservation

Most organisms do not become fossils…

• Two conditions are important for preservation: rapid burial and the possession of hard parts.

What are the different kinds of fossils?

a. Amber

Amber

#1 Amber

b. Asphalt&

Tar

#2 Asphalt/Tar

□Asphalt wells up in thick sticky pools.

□Trapped and preserved organisms in asphalt.

c. Petrified

#3 Petrified Fossils

□A process in which minerals replace the organism’s tissues.□Different types:

□Pore space in bone/wood fills up with mineral

□Organisms tissues are replaced by minerals

d. Frozen

#4 Frozen

e. Molds &

Casts

Molds and Casts

VI. Environments

a. Interpreting Environments

• Fossils can also be used to interpret and describe ancient environments and changes that occurred (polar areas once being tropical)

• They can identify extinct species and effects of catastrophism (floods, volcanic eruptions, earthquakes).

• They can describe geologic changes (mountains once under water, Pangaea)

Shark tooth in Georgia?!?!

b. Fossils on a Mountaintop?

□Rocks on the mountain formed at the bottom of the ocean.

□Using fossils, scientists can tell whether the climate was cooler or more wet than present.