Petrified RemainsPetrified Remains

Hard and rock likeHard and rock like Original material replaced by mineralsOriginal material replaced by minerals Ex. bones, woodEx. bones, wood

Carbonaceous FilmsCarbonaceous Films Burial forces gases and Burial forces gases and

liquid outliquid out Forms thin film of carbon Forms thin film of carbon

residueresidue Outline of organismOutline of organism Ex. plantsEx. plants

Mold & CastMold & Cast Organism is buriedOrganism is buried Outside decays leaves a Outside decays leaves a

cavity = moldcavity = mold Sediment fills in mold and Sediment fills in mold and

hardens to rock = casthardens to rock = cast

The cast looks like the organism!

Original RemainsOriginal Remains actual or part of organismactual or part of organism trapped in Amber – insectstrapped in Amber – insects frozen – woolly mammothfrozen – woolly mammoth tar pitstar 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 FossilsTrace Fossils

evidence of animal activityevidence of animal activity tells how organism livestells how organism lives Ex. tracks, worm holesEx. tracks, worm holes

These are dinosaur foot prints!!Worm tracks! ↓

Index FossilsIndex 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 timeExisted for a short period of time Were abundant, there were many of themWere abundant, there were many of them Lived all over the worldLived all over the world

TRILOBITE

EUOMPHALUS

But wait…. There’s more….

Finding Clues to Finding Clues to Rock LayersRock Layers

Activity!!!Activity!!!

You be the dective!You be the dective!

You be the Detective!You be the Detective!

Fossil clues give geologists a good idea of Fossil clues give geologists a good idea of what life on earth was like millions or even what life on earth was like millions or even billions of years ago!billions of years ago!

Problem: How can YOU use fossils and Problem: How can YOU use fossils and geologic features to interpret the relative ages geologic features to interpret the relative ages of rock layers?of rock layers?

1. What “fossil clues” in layers A and B indicate the kind 1. What “fossil clues” in layers A and B indicate the kind of environment that existed when these rock layers were of environment that existed when these rock layers were formed? How did the environment change in layer D?formed? How did the environment change in layer D?

Fossils of marine animals in A and BFossils of marine animals in A and B In layer D – Dinosaur tracks and a leaf = landIn layer D – Dinosaur tracks and a leaf = land

2. Which layer is the oldest? How do you know?2. Which layer is the oldest? How do you know?

A is the oldest because the law of Superposition A is the oldest because the law of Superposition states that the lowest layer is the oldest.states that the lowest layer is the oldest.

3. Which of the layers formed most recently? How do you 3. Which of the layers formed most recently? How do you know? know?

Layer G formed most recently because the law of Layer G formed most recently because the law of superposition states that the highest layer is the superposition states that the highest layer is the youngest.youngest.

4. Why are there no fossils in layers C and E?4. Why are there no fossils in layers C and E?

Layers C and E are extrusions of igneous rock Layers C and E are extrusions of igneous rock (igneous rocks do not contain fossils)(igneous rocks do not contain fossils)

5. What kind of fossils occurred in layer F?5. What kind of fossils occurred in layer F?

Dinosaur, Plant, and bird fossilsDinosaur, Plant, and bird fossils

Site 2Site 26. Which layer at Site 1 might have formed at the same 6. Which layer at Site 1 might have formed at the same

time as layer W at Site 2? How do you know?time as layer W at Site 2? How do you know?

Layer BLayer B Have the same type of fossils!Have the same type of fossils!

7. What clues show an unconformity or gap in the 7. What clues show an unconformity or gap in the horizontal rock layers? What might have happened to horizontal rock layers? What might have happened to

these rock layers?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? 8. Which is older, intrusion V or layer Y? How do you know?How do you know?

Layer Y is olderLayer Y is older An intrusion is always younger that the layers it An intrusion is always younger that the layers it

passes throughpasses through

9. Working as a geologist, you find a rock containing 9. Working as a geologist, you find a rock containing fossils. What information would you need in order to fossils. What information would you need in order to

determine the rock’s age relative to one of the rock layers determine the rock’s age relative to one of the rock layers at Site 1?at Site 1?

You would need to know if any layers at Site 1 You would need to know if any layers at Site 1 contained the same index fossils.contained the same index fossils.