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.
GRAND
CANYON FOSSILS
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
Kaibab
Toroweap
Limestone, sandstone
Coconino
Sandstone
Hermit
Shale
Supai
Sandstone, siltstone,
shale, dolomite
Redwall
Limestone
Limestone, sandstone
Temple Butte
Limestone
Muav
Limestone
Bright Angel
Shale
Tapeats
Sandstone
Vishnu, etc.
Metamorphic and igneous rocks, no fossils
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
54
Inv. 7: Fossils and Time
Student Sheet
Name
Period
Date
INDEX-FOSSIL
IDENTIFICATION, GRAND CANYON
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
Rock layer
Index fossils identified
Ages
Kaibab
Formation
Toroweap
Formation
Coconino
Sandstone
Hermit Shale
Supai Group
Redwall
Limestone
Temple Butte
Limestone
Muav
Limestone
Bright Angel
Shale
Tapeats
Sandstone
Vishnu
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
55
Inv. 7: Fossils and Time
Student Sheet
BRYCE
CANYON FOSSILS
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
B9
Coal, sandstone
B8
Shale
B7
B6
B5
Sandstone
Shale
B4
Sandstone
B3
Shale, sandstone, limestone
B2
Sandstone
B1
Shale, conglomerate
Shale, sandstone
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
56
Inv. 7: Fossils and Time
Student Sheet
ZION
NATIONAL PARK FOSSILS
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
Z7
Shale, sandstone, limestone
Z6
Sandstone
Z5
Shale, sandstone
Z4
Sandstone
Z3
Shale, conglomerate
Z2
Shale, limestone
Z1
Limestone, sandstone
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
57
Inv. 7: Fossils and Time
Student Sheet
Name
Period
Date
Shale
Sandstone
Metamorphic and igneous rocks, no fossils
Bright Angel
Tapeats
Vishnu, etc.
Limestone
Limestone
Muav
Limestone
Redwall
Temple Butte
Sandstone, siltstone,
shale, dolomite
Supai
Sandstone
Shale
Coconino
Hermit
Limestone, sandstone
Kaibab
Toroweap
Limestone, sandstone
INDEX-FOSSIL
CORRELATIONS
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
Grand Canyon
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
59
Inv. 7: Fossils and Time
Student Sheet
Zion National Park
Bryce Canyon
Cut these rock layers out on the dashed lines and tape
them to the Index-Fossil Correlations sheet to observe
the relationship of the rocks in the three national parks.
B9
Coal, sandstone
B8
Shale
B7
B6
B5
Shale
B4
Sandstone
B3
Shale, sandstone, limestone
B2
Sandstone
B1
Shale, conglomerate
Sandstone
Shale, sandstone
Z7
Shale, sandstone, limestone
Z6
Sandstone
Z5
Shale, sandstone
Z4
Sandstone
Z3
Shale, conglomerate
Z2
Shale, limestone
Z1
Limestone, sandstone
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
61
Inv. 7: Fossils and Time
Student Sheet
Name
Period
Date
INDEX-FOSSIL
CORRELATION QUESTIONS
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
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 you
know?
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?
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
63
Inv. 7: Fossils and Time
Student Sheet
Name
Period
Date
THINKING
ABOUT INDEX FOSSILS
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
1. What big ideas did the following people contribute to the study of fossils? How did
their 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?
3. Smith noticed that wherever he found his index fossils, fossil a was always in the top
layer, fossil b was in the layer under a, and fossil c was in the layer under b. One time
he found a rock column with fossil a in the top layer and fossil c in the layer directly
under layer a. There was no layer with fossil b. What might this mean? How would
you find out for sure? Draw a picture to help you think about this.
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
65
Inv. 7: Fossils and Time
Student Sheet
4. Suppose you found a rock column with fossil c in the top layer, with fossil b in the next
layer, and fossil a in the lowest layer. What might this mean? How would you find out
for sure?
5. This illustration shows what might be a typical column of rocks exposed in a canyon on
the Colorado Plateau. Using potassium-argon dating, geologists have calculated an age
of 200 million years for rock A, a granite. Rock F, the volcano, has been given an age of
225,000 years.
F
Volcano
di
ke
—
—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –Canyon
– –—
– –—
– –—
– –—
– –—
–
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
– –—
–
Shale
E
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—
– –—–
—
. –. .–. –. .–. .–. –. .–. .–. –. .–. –
. . –. .–. –. .–. .–. –. .–. .–. –. .–. –
. . –. .–. –. .–. .–. –. .–. .–. –. .–. –
. . –. .–. –. .–. .–. –. .–. .–. –. .–. –
. . –. .–. –. .–. .–. –. .–
Ba
sa
lt
.........................................................................................................................................................................................................................................................
...................................................................Sandstone
.................D
................................
........................................................................................................................................................................................................................
C
Limestone
......................................................................................................................................................................
...................................................................Sandstone
. . . . . . . . . . . . . . . . . ................................................................
........................................................................................................................B
................................
......................................................................................................................................................................................................
Schist and granite
A
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?
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
66
Inv. 7: Fossils and Time
Student Sheet
EVENT
CARDS A
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
Archaeopteryx
(early bird)
First flowering plants
Forests
of coal
plants
First crocodiles
Recorded written history
Water appeared on
Earth’s surface
First mammals
Pangaea, the supercontinent,
begins to divide
First sharks
Neanderthal man
(1400 cc brain)
First bony fishes
Protozoa (single-celled,
microscopic animals)
Trilobites
Dinosaur extinction
Grass
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
67
Inv. 7: Fossils and Time
Student Sheet
EVENT
CARDS B
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
Pangaea, the supercontinent,
forms
Jellyfish appear
Bees
First reptiles
First dinosaurs
Great Extinction
First insects
First land animals
Earliest life (bacteria-like)
Tyrannosaurus rex
First amphibians
First vascular land plants
(plants with roots and stems)
Modern
horse
Earth formed
First vertebrates (jawless
fish with skeletons made of
cartilage)
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
69
Inv. 7: Fossils and Time
Student Sheet
Name
Period
Date
MAJOR
EVENTS IN EARTH HISTORY
○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
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 to
your partner why you are putting them in that order. Reach an agreement about the order
and record the sequence here.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
______________________________
_______________________________
_______________________________
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
________________________________________
________________________________________
________________________________________
________________________________________
________________________________________
________________________________________
________________________________________
________________________________________
________________________________________
________________________________________
________________________________________
________________________________________
________________________________________
________________________________________
________________________________________
After you have recorded your sequence, place the cards on your time lines where you think
they should go.
FOSS Earth History Course
© The Regents of the University of California
Can be duplicated for classroom or workshop use.
71
Inv. 7: Fossils and Time
Student Sheet