Petrified Remains Hard and rock like Hard and rock like Original material replaced by minerals Original material replaced by minerals Ex. bones, wood Ex. bones, wood

Carbonaceous Films Burial forces gases and Burial forces gases and liquid out Forms thin film of carbon Forms thin film of carbonresidue Outline of organism Outline of organism Ex. plants Ex. plants

Mold & Cast Organism is buried Organism is buried Outside decays leaves a Outside decays leaves a cavity = mold Sediment fills in mold and Sediment fills in mold and hardens to rock = cast The cast looks like the organism!

Original Remains actual or part of organism actual or part of organism trapped in Amber – insects trapped in Amber – insects frozen – woolly mammoth frozen – woolly mammoth tar pits tar pits

What is a tar pit??? What is a tar pit??? Los Angeles La Brea Tar Pits This is a recreation of a tar pit that illustrates how animals would get trapped in tar pits.

Trace Fossils evidence of animal activity evidence of animal activity tells how organism lives tells how organism lives Ex. tracks, worm holes Ex. tracks, worm holes These are dinosaur foot prints!! Worm tracks! ↓

Index Fossils Used to date other fossils and rock layers. Used to date other fossils and rock layers. Fossils of animals that Fossils of animals that Existed for a short period of time Existed for a short period of time Were abundant, there were many of them Were abundant, there were many of them Lived all over the world Lived all over the world TRILOBITE EUOMPHALUS But wait…. There’s more….

Finding Clues to Rock Layers Activity!!! You be the dective!

You be the Detective! Fossil clues give geologists a good idea of what life on earth was like millions or even billions of years ago! Fossil clues give geologists a good idea of what life on earth was like millions or even billions of years ago! Problem: How can YOU use fossils and geologic features to interpret the relative ages of rock layers? Problem: How can YOU use fossils and geologic features to interpret the relative ages of rock layers?

1. What “fossil clues” in layers A and B indicate the kind of environment that existed when these rock layers were formed? How did the environment change in layer D? Fossils of marine animals in A and B Fossils of marine animals in A and B In layer D – Dinosaur tracks and a leaf = land In layer D – Dinosaur tracks and a leaf = land

2. Which layer is the oldest? How do you know? A is the oldest because the law of Superposition states that the lowest layer is the oldest. A is the oldest because the law of Superposition states that the lowest layer is the oldest.

3. Which of the layers formed most recently? How do you know? Layer G formed most recently because the law of superposition states that the highest layer is the youngest. Layer G formed most recently because the law of superposition states that the highest layer is the youngest.

4. Why are there no fossils in layers C and E? Layers C and E are extrusions of igneous rock (igneous rocks do not contain fossils) Layers C and E are extrusions of igneous rock (igneous rocks do not contain fossils)

5. What kind of fossils occurred in layer F? Dinosaur, Plant, and bird fossils Dinosaur, Plant, and bird fossils

Site 2 6. Which layer at Site 1 might have formed at the same time as layer W at Site 2? How do you know? Layer B Layer B Have the same type of fossils! Have the same type of fossils!

7. What clues show an unconformity or gap in the horizontal rock layers? What might have happened to these rock layers? Rock layers that are missing from the sequence - Site 2 provide clues of an unconformity. Layers E and D are missing between layers X and Y, which suggests an unconformity. Layer A is also missing, which suggests an unconformity below W. So…Erosion might have occurred because there are missing layers in site 2!

8. Which is older, intrusion V or layer Y? How do you know? Layer Y is older Layer Y is older An intrusion is always younger that the layers it passes through An intrusion is always younger that the layers it passes through

9. Working as a geologist, you find a rock containing fossils. What information would you need in order to determine the rock’s age relative to one of the rock layers at Site 1? You would need to know if any layers at Site 1 contained the same index fossils. You would need to know if any layers at Site 1 contained the same index fossils.