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1. Fossils & The Geologic
Time Scale

2. OBJECTIVES:
•At the end of lesson, the learners are expected to:
–Acquire familiarity with the Geologic
Time Scale,
–Describe how fossils are used to identify
subdivision of the geological time scale,
–Explain how fossils have been used to
define and identify subdivisions of the
geologic time scale.

3. Say Something…………..
•Geological Time Scale
• Fossil
•History
•Era
•Rock
•Cenozoic
•Pre-Cambrian
•Periods

4. 1.What are the major
divisions of the geological
time scale?
2. What are the significant
event during, Paleozoic
Era, Mesozoic Era, and
Cenozoic Era?

5. Stratigraphy and Evolution:
Using Fossils to Tell "Deep
Time”
Procedure:
•Divide the class into 4 groups.
•Each group will have a set of
cards/print-outs representing fossil
assemblages from different rock layers.

6. • Remember : Foraminifera are mostly
marine microscopic, single celled organisms
that have calcareous shells. When the
organism dies, the shells or tests become part
of the sediment record. Foraminifers are
important index fossils — abundant,
widespread, distinctive, and have relatively
limited geologic time range.

7. •
Each group will
arrange the cards in
order from oldest to
youngest.

9. Guide Questions
•What is the essential role of fossils in subdividing
the Geologic Time?
•What is the sub-discipline of stratigraphy which
deals with the use of fossils in correlation and
establishing the relative ages of rocks?
•What is index fossil?
•How did the scientist assigned numerical dates in
the geological time scale?

10. Fossils
•Preserved remains or traces of an organism
that lived in the past.
•Fossils are formed when organisms die and are
buried in sediment. Eventually the sediment
builds up and hardens to become sedimentary
rock.
•Sediments are pieces of solid material that have
been deposited on Earth’s surface by wind, ice,
gravity, or chemical precipitation.
•Paleontologist-scientist who study the remains
of organisms in the rock record.

11. Index fossils
•are the remains of plants and animals that
lived for a limited period. Best index fossils
are common, widely distributed, and easy to
identify. Some of the most common index
fossils are ammonites, trilobites, and
graptolites.

13. Kinds of fossils
•Petrified - when minerals replace the remains and
they become rock things like wood.
•Mold - when the shell remains and the contents
dissolve (hollow) like in art class you use a mold
to get the correct shape of a bowl.
•Cast - when the mold becomes filled with minerals
that are not a part of the original organism.
•Index- a fossil found in a narrow time range but
widely distributed around the earth;used to date
rock layers.
•Trace fossil-a fossilized mark that is formed in soft
sediment by the movement or actions of an animal.

14. PETRIFIED MOLD
CAST

15. •Sometimes whole animals become preserved
intact, but this is very rare. If an organism is
surrounded by ice or tar they might be discovered
looking much the same as they did when they
died.
AETOSAUR
FOUND IN
THE
NATIONAL
PETRIFIED
FOREST

16. Relative Dating
Relative dating: looks at where the fossil is
located to determine its age relative to other
fossils. This only works if the area has
been undisturbed.

17. Absolute Dating
•Uses radioactive elements near the fossils
to determine the actual age of the fossils.
•By determining the age of the radioactive
element, scientists can calculate the age of the
fossil buried nearby.
The absolute age
of fossils is
estimated by
dating associated
igneous rock and
lava flows.

18. Fossil Record
•The dating of all
fossils is included in
the Geological Time
Scale. This scale
divides the time that
the earth has existed
into 4 eras.
•Eras are then divided
into periods based on
common events in
that time period.

19. Vocabulary
1.geologic time scale – a model scientists use to
describe the timing of events and the relationships
between those events in earth’s history.
2.era – one of three long periods of geologic time
from Precambrian to the present.
3.period – geologic time periods that eras are
divided into.
4. epoch – a division of geologic time; a subdivision
of a period.

20. Pre-
Cambrian
•Began with the
formation of the
Earth 4.6 billion
years ago.
•Bacteria
appeared 3.5
billion years
ago, followed
by algae and
fungi.

21. Paleozoic Era
•Divided into 5 periods:
•Cambrian period -
Sponges, snails, clams
and worms evolve
•Ordovician period -
First fishes evolved and
other species become
extinct
•Silurian period - Land
plants, insects and
spiders appear

22. •Devonian period -
Amphibians evolve and
cone-bearing plants start to
appear.
•Carboniferous period -
Tropical forests appear and
reptiles evolve.
•Permian period - Seed
plants become common
and insects and reptiles
become widespread. Sea
animals and some
amphibians begin to
disappear.

23. Mesozoic Era
•Divided into 3 periods:
•Triassic period - Turtles
and crocodiles evolve and
dinosaurs appear.
•Jurassic period - Large
dinosaurs roam the world.
First mammals and birds
appear.
•Cretaceous period -
Flowering plants appear,
mammals become more
common, dinosaurs
• become extinct.

24. Cenozoic Era
•Divided into 2 periods:
•Tertiary period - First
primates appear and
flowering plants become
the most common.
•Quaternary period -
Humans evolve and
large mammals like
woolly mammoths
become extinct.

26. 1. What does the geologic time scale represent?
 
A.The theorized development of life on earth
dating back 4.6 billion years ago.
B.The age of the earth and all creatures on it.
C.The geologic history of universe.
D.The fossil record as we know it.

27. 2. What is a fossil?
 
A.An imprint or hollow in a rock, shaped like an
organism
B.Hardened tree sap
C.A mold filled with hardened sediments
D.The remains or traces of an organism that lived long
ago.

28. 3.What is an important index fossil for the
Paleozoic Era?
A.fish
B. trilobtes
C. plants
D.sponge

29. 4. Which of the following animal parts would
be most likely to form a fossil?
A.Blood
B.skin
C. bones
D. fur

30. 5. Where does fossils usually found?
A.Lava
B.Igneous rock
C.Metamorphic rock
D.Sedimentary rock

31. 6. Which of the following is an example
of a trace fossil?
A.Skeleton
B.Trilobite
C. Footprint
D. Leaf

32. 7. ________ are remains of species that existed on
earth for a relatively short period of time, were
abundant, and were widespread geographically.
A.Casts
B.Index fossils
C.Half-lives
D.unconformities

33. 8. A fossilized dinosaur foot print is an example
of
A.a mold
B.A trace fossil
C.Index fossil
D.A cast

34. 9. Which of the following is the youngest rock
layer in the “Index Fossil Correlation”?
A.Hermit shale
B.Z4
C.Z6
D.B6

35. 10. Which of the following organisms formed
last on Earth?
A.Jellyfish
B.Shark
C.Lizard
D.Horses