Notes
SPI 0807.5.5
Fossils
Science
What Are Fossils?
Fossils are the preserved physical remains of deceased
organisms that are at least 10,000 years old
 NOTE: Most organisms DO NOT become fossils after death
 NOTE: The formation of fossils is a RARE event
How Are Fossils Formed?
Watch this amusing video: Link: Video: How Fossils Are Made
Primate Fossil:
47 million years old
Whale Fossil:
25 million years old
Notes
SPI 0807.5.5
Fossils
Science
8 Types of Fossils
A) Fossils In Rocks
B) Fossils In Amber
C) Petrified Fossils
D) Fossils In Asphalt
E) Frozen Fossils
F) Trace Fossils
G) Mold/Cast Fossils
H) Index Fossils
Notes
SPI 0807.5.5
Fossils
Science
A) Fossils In Rocks
 Found in sedimentary rock
 An organism died –was covered with mud, dirt, sand, ash, etc.
 Later the mud, dirt, sand, or ash became sedimentary rock
Notes
SPI 0807.5.5
Fossils
Science
B) Fossils In Amber
 Tree sap fell on a small organism, enclosed it, killed it
 Over time the sap hardened into amber
 The amber became covered with mud, dirt, sand, ash, etc.
Example:
Insects In Amber
Notes
SPI 0807.5.5
Fossils
Science
C) Petrified Fossils (Also known as petrifaction)


Organism died- then was covered with mud, dirt, sand, ash, etc.
The structure of the organism was replaced with minerals
Sometimes when wood is buried, groundwater will flow through the
sediment and deposit minerals in the cells of the wood.
The wood rots away & the minerals remain in the shape of the tree.
Example:
Petrified Wood
Example:
Petrified Wood
Notes
SPI 0807.5.5
Fossils
Science
D) Fossils In Asphalt
 Animals fell into tar pits, were trapped, and died
 The asphalt hardened preserving skeletons, shells, teeth, etc.
Saber Tooth Tiger Fossil
(From La Brea Tar Pits, California)
Notes
SPI 0807.5.5
Fossils
Science
E) Frozen Fossils
 Animals died in a cold climate region and were frozen
 The cold temperatures preserved both soft and hard parts
 Many mammoths became frozen during the last ice age
Frozen Baby Mammoth
(From Siberia, Russia)
Approx. 42,000 yrs old
Frozen Baby Mammoth
(From Siberia, Russia)
Approx: 40, 000 yrs old
Notes
SPI 0807.5.5
Fossils
Science
F) Trace Fossils
(Also called ichnofossils)
 Are impressions or “traces” left by plants and animals
 Can be simple tunnels or burrows in the mud
 Can be footprints or imprints in the mud etc.
Trace Fossil
Dinosaur footprints
Trace Fossil
Imprint Of A Fish
Notes
SPI 0807.5.5
Fossils
Science
G) Mold/Cast Fossils
 In sediment, ground water may dissolve shells, leaving a
shape called a mold
 Sometimes the shell dissolves and is replaced by minerals,
leaving behind a mineral cast of the fossil
Mold Fossil
Cast Fossil
Notes
SPI 0807.5.5
Fossils
Science
H) Index Fossils
 A way to relatively date rocks (A.K.A. relative dating)
 Some fossils are commonly found at certain strata levels
across large geographic areas …we call these index fossils
Example:
Ammonite fossils
Example:
Trilobite fossils