Earth History Investigation 7 : Fossils and TimeHistory...Name: Hr: Earth History Investigation 7 : Fossils and Time Part One: Index Fossils Fossils provide geologists with important

Name: Hr:

Earth History Investigation 7 : Fossils and Time

Part One: Index Fossils Fossils provide geologists with important evidence about prehistoric environments. Some fossils also provide evidence for age of rock layers. These fossils are called index fossils. Not all fossils are index fossils. An index fossil must have lived for a relatively short period of time and in many places. An index fossil should be distributed over a wide geographical area to be useful. For example, some of the same index fossils are found in rocks of Devonian age in both the Grand Canyon and the Midwest. If geologists identify an index fossil in a rock layer, they can be pretty sure of the age of the rock layer in which it was found. They know it is about the same age as any other rock layers that contain the same index fossil. A fossil that lived for only a million years or so would be a good index fossil. You would know that any rocks containing that fossil are no more than a million years different in age. Which would make a better index fossil, a fern that has lived on Earth since the Pennsylvanian period, 300 mya, or a trilobite that lived in many areas for only a few million years during the Cambrian period? If musicians were index fossils, which would make a better index fossil, Elvis Presley or Milli Vanili? Lab Sheet – Grand Canyon Fossils p Index Fossil Key – Earth History Resources book Early – the time at the beginning of a geological period. Late – the end of a time period. Lab Sheet – Index-Fossil Identification, Grand Canyon p Labsheet – Bryce Canyon Fossils and Zion National Park Fossils p If you find the same index fossil at both the Grand Canyon and Zion, what does that tell you about the age of the layers in which the fossils are found? Labsheet – Index-Fossil Correlations p Labsheet – Index Fossil Correlation Questions p

Read A Fossil Primer in Earth History Resources book. Labsheet – Thinking about Index Fossils p Part Two – Earth History Sequence Cards What important discovery allowed geologists to add numbers to the relative time scale? Imagine an organism from the past that is now extinct. It did not leave any fossils. How would we know that it ever existed? How do we know what organisms and environments existed in the past? Labsheet – Event Cards A & B p

1. Cut out the cards. You only need one set of cards per pair. 2. Work together to arrange the cards in order. You should use what you know from the

investigations we have done so far and other information that you have notes about from past investigations.

3. Work for a few minutes. Then answer the four questions at the top of the Major Events in Earth history page. P

4. After you have reached an agreement on the order, record them on Major Events in Earth history, p

Where were some of the easiest cards to put in sequence? Which ones were the hardest to sequence? Which cards caused the most disagreement in your pair? What other information would be helpful to you in sequencing the cards?

Journal Writing What surprised you about the correct sequence of event cards? What have you learned from making your time line and sequencing the event on it about the appearance of different life-forms on Earth? Review for Mid-summative Exam Know that the most important use of index fossils to geologists is. Know how to decide what layers are older than others by looking at the fossils in each layer. Know how to use index fossils to decide how old layers of rocks are and what period fossils above and below it came from.

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FOSS Earth History Course© The Regents of the University of CaliforniaCan be duplicated for classroom or workshop use.

Limestone

Metamorphic and igneous rocks, no fossils

Sandstone

Shale

Limestone

Limestone

Sandstone, siltstone, shale, dolomite

Shale

Sandstone

Limestone, sandstone

Limestone, sandstoneKaibab

Toroweap

Coconino

Hermit

Supai

Redwall

Temple Butte

Muav

Bright Angel

Tapeats

Vishnu, etc.

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GRAND CANYON FOSSILS

Inv. 7: Fossils and TimeStudent Sheet

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Rock layer Index fossils identified Ages

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INDEX-FOSSIL IDENTIFICATION, GRAND CANYON

Name

Period Date

KaibabFormation

ToroweapFormation

CoconinoSandstone

Hermit Shale

Supai Group

RedwallLimestone

Temple ButteLimestone

MuavLimestone

Bright AngelShale

TapeatsSandstone

Vishnu


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Shale

Coal, sandstone

Shale

Sandstone

Shale, sandstone

Sandstone

Shale, sandstone, limestone

Sandstone

Shale, conglomerate

B3

B9

B8

B7B6B5

B4

B2

B1

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BRYCE CANYON FOSSILS


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ZION NATIONAL PARK FOSSILS



Shale, limestone

Shale, conglomerate

Sandstone

Shale, sandstone


Sandstone

Z7

Z6

Z5

Z4

Z3

Z2

Z1

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INDEX-FOSSIL CORRELATIONS

Name

Period Date

L

imes

tone

Met

amor

phic

and

igne

ous

rock

s, n

o fo

ssils

S

ands

tone

S

hale

Lim

esto

ne

Lim

esto

ne

San

dsto

ne, s

iltst

one,

sha

le, d

olom

ite

Sha

le

San

dsto

ne

Lim

esto

ne, s

ands

tone

Lim

esto

ne, s

ands

tone

Kaib

ab

Toro

weap

Cocon

ino

Herm

it

Su

pai

Redw

all

Tem

ple

Butt

e

Muav

Bri

gh

t A

ngel

Tap

eats

Vis

hn

u,

etc

.

Grand Canyon


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Cut these rock layers out on the dashed lines and tapethem to the Index-Fossil Correlations sheet to observethe relationship of the rocks in the three national parks.

Shale

Coal, sandstone

Shale

Sandstone

Shale, sandstone

Sandstone


Sandstone

Shale, conglomerate

B3

B9

B8

B7B6B5

B4

B2

B1

Bry

ce C

an

yon

Zio

n N

ati

onal P

ark



Shale, limestone

Shale, conglomerate

Sandstone

Shale, sandstone


Sandstone

Z7

Z6

Z5

Z4

Z3

Z2

Z1

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Answer these questions after you have identified and correlated the rock layers at the three parks.

1. Which rock layers contained the same index fossils at Zion and the Grand Canyon?

2. Which rock layers contained the same index fossils at Zion and Bryce?

3. Which rock layers contained the same index fossils at Grand Canyon and Bryce?

4. Is rock layer B3 at Bryce older or younger than Supai Group at the Grand Canyon? How do youknow?

5. Is rock layer B2 at Bryce older or younger than rock layer Z1 at Zion? How do you know?

6. What do you think the environment was like at the time layer B9 was being deposited at Bryce?

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INDEX-FOSSIL CORRELATION QUESTIONS

Name

Period Date


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1. What big ideas did the following people contribute to the study of fossils? How didtheir ideas help people better understand fossils and what they mean?

a. James Hutton

b. Lamarck

c. William Smith

2. Fossils have been called the index to Earth history. What does that mean?

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THINKING ABOUT INDEX FOSSILS

Name

Period Date

3. Smith noticed that wherever he found his index fossils, fossil a was always in the toplayer, fossil b was in the layer under a, and fossil c was in the layer under b. One timehe found a rock column with fossil a in the top layer and fossil c in the layer directlyunder layer a. There was no layer with fossil b. What might this mean? How wouldyou find out for sure? Draw a picture to help you think about this.


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4. Suppose you found a rock column with fossil c in the top layer, with fossil b in the nextlayer, and fossil a in the lowest layer. What might this mean? How would you find outfor sure?

5. This illustration shows what might be a typical column of rocks exposed in a canyon onthe Colorado Plateau. Using potassium-argon dating, geologists have calculated an ageof 200 million years for rock A, a granite. Rock F, the volcano, has been given an age of225,000 years.

a. How can you use this information to estimate the age of rock layers B, C, D, and E?

b. Which is younger, the volcano or the basalt dike leading up to it?

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— — — — — — — — — — — — — — — — — — — — — — — — — — – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –— — — — — — — — — — — — — — — — — — — — — — — — — — – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –— — — — — — — — — — — — — — — — — — — — — — — — — — – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –— — — — — — — — — — — — — — — — — — — — — — — — — — – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

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B

C

D

E

F

Schist and granite

Sandstone

Limestone

Shale

Volcano

Sandstone

Canyon

Basa

lt di

ke


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Archaeopteryx(early bird)

Forests of coal plants

First crocodiles Recorded written history

First mammals First sharks

First bony fishes Protozoa (single-celled,microscopic animals)

Pangaea, the supercontinent,begins to divide

Dinosaur extinction

Water appeared onEarth’s surface

Neanderthal man(1400 cc brain)

Grass

First flowering plants

Trilobites

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EVENT CARDS A


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Pangaea, the supercontinent,forms

Jellyfish appear

First reptiles Great Extinction

First land animals Earliest life (bacteria-like)

Tyrannosaurus rex First amphibians First vascular land plants(plants with roots and stems)

Earth formed First vertebrates (jawlessfish with skeletons made of

cartilage)

Modernhorse

First dinosaurs

Bees

First insects

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EVENT CARDS B


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Consider the following pairs of events. Which do you think occurred first in each pair?Explain why you think so.

• Dinosaurs appear; dinosaurs become extinct.

• Jellyfish appear; protozoa (single-celled animals) appear.

• Bees appear; flowering plants appear.

• Trilobites appear; fish with backbones appear.

Take turns arranging the event cards in the order they might have occurred. Explain toyour partner why you are putting them in that order. Reach an agreement about the orderand record the sequence here.

1. ______________________________ 16. ________________________________________ 2. ______________________________ 17. ________________________________________ 3. ______________________________ 18. ________________________________________ 4. ______________________________ 19. ________________________________________ 5. ______________________________ 20. ________________________________________ 6. ______________________________ 21. ________________________________________ 7. ______________________________ 22. ________________________________________ 8. ______________________________ 23. ________________________________________ 9. ______________________________ 24. ________________________________________10. ______________________________ 25. ________________________________________11. ______________________________ 26. ________________________________________12. ______________________________ 27. ________________________________________13. ______________________________ 28. ________________________________________14. _______________________________ 29. ________________________________________15. _______________________________ 30. ________________________________________

After you have recorded your sequence, place the cards on your time lines where you thinkthey should go.

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MAJOR EVENTS IN EARTH HISTORY

Name

Period Date


Documents

Earth History Investigation 7 : Fossils and TimeHistory...Name: Hr: Earth History Investigation 7 : Fossils and Time Part One: Index Fossils Fossils provide geologists with important