Index Fossils

What are Fossils?

• Preserved remains or traces of living things.

• They help show how the Earth has changed over time.

• They are clues to what the environment was like in the past.

TRACE FOSSILS

TRUE FORM FOSSILS

MOLD FOSSILS & CAST FOSSILS

CASTMOLD

How do Fossils Form?

1. The animal dies.

2. The remains are buried in sediment.

3. The sediment turns to rock and preserves the shape or trace of the animal.

• Usually found in Sedimentary Rocks.

How is a Fossil Created?

What is an Index Fossil?

• Index fossils are used to help Geologists match different rock layers that may be located far apart.

• Helps to tell the relative age of the rock layers.

What makes a Fossil an Index Fossil?

1. The fossil must be found in a lot of locations around the globe.

2. They must have lived during a distinct time period. That means Scientists know that they lived and became extinct during a set time period. They’re not found in every layer, just one layer.

Find the Index Fossils?

BECAUSE IT’S FOUND IN ONLY ONE LAYER OF ROCK, WE CAN INFER THAT THIS

ANIMAL LIVED AND BECAME EXTINCT IN A SHORT AMOUNT OF TIME. THAT MAKES IT

A GOOD INDEX FOSSIL.

Find the Index Fossils?

THOUSANDS OF MILES

APART

BECAUSE THE FOSSIL IS FOUND IN LAYERS IN DIFFERENT PLACES ON THE EARTH IT MAKES A GOOD INDEX FOSSIL.

Here’s how index fossils work.

Now lets try to use index fossils to figure out the relative age of some rock layers as a team.