II. What are Fossils?
Fossils are the remains or traces of
prehistoric life. They are important
components of sediment and
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
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
• Molds and casts are another common type
• Carbonization is particularly effective in
preserving leaves and delicate animals. It
occurs when an organism is buried under
a. Trace fossils are indirect
evidence of prehistoric
Can tell us about the activity,
habitat, diet, etc. of an animal
Examples: Tracks, shelters, and
III. Indirect evidence
Not the ACTUAL Fossil!
IV. Preserved Fossil Types
Conditions Favoring Preservation
Most organisms do not
• Two conditions are important for
preservation: rapid burial and the possession
of hard parts.
What are the different kinds of
□ Asphalt wells up in
thick sticky pools.
□ Trapped and
#3 Petrified Fossils
□ A process in which
minerals replace the
□ Different types:
□Pore space in bone/wood
fills up with mineral
□Organisms tissues are
replaced by minerals
Molds and Casts
a. Interpreting Environments
• Fossils can also be used to interpret and
describe ancient environments and
changes that occurred (polar areas once
• They can identify extinct species and
effects of catastrophism (floods, volcanic
• 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
fossils, scientists can
tell whether the
climate was cooler
or more wet than