1. T5 Fossils & the Rock Records
...it’s as old as the hills.
PowerPoint Notes created by S. Koziol
Date : 12/1/2013 Revised : ?/?/??

2. Part 1 Objectives Describe the geological time scale
Distinguish among the following time scale divisions: eon, era, period & epoch.

3. Time Scale – To be Completed
The geologic time scale divides Earth’s history into units from its origin to the present.
Era
Period
Epoch
Began (MYA)
Cenozoic
Quaternary
Holocene
Pleistocene
1.806
Pliocene
5.332
Miocene
23.03
Oligocene
33.9
Eocene
55.8
Paleocene
65.5
Mesozoic
Cretaceous
145.5
Jurassic
199.6
Triassic
251.0
Paleozoic
Permian
299.0
Carboniferous Pennsylvanian
318.1
Carboniferous Mississippian
359.2
Devonian
416.0
Silurian
443.7
Ordovician
488.3
Cambrian
542.0
Precambrian time
4600
Adapted from Modern Earth Science, 2002, Holt, Rinehart and Winston
Time Scale
Time Scale – To be Completed

4. Blank Time Scale Era Period Epoch Began (millions of years)
Characteristics from geologic and fossil evidence
Connecticut Valley Geological Events
1.806
5.332
23.03
33.9
55.8
65.5
145.5
199.6
251.0
Blank Time Scale

5. Time Scale Continued Era Period Began (millions of years)
Characteristics from geologic and fossil evidence
Connecticut Valley Geological Events
299.0
318.1
359.2
416.0
443.7
488.3
542.0
4568
Time Scale Continued

6. Time Scale Continued Era Period Began (millions of years)
Characteristics from geologic and fossil evidence
Connecticut Valley Geological Events
Paleozoic
Ancient Life
Permian
299.0
 Major extinction of 95% of marine species
Pennsylvanian
318.1
 First reptiles & extensive c.s.f.
Mississipian
359.2
 First coal swamp forests
Devonian
416.0
 First amphibians.
Silurian
443.7
 large reefs appear
Ordovician
488.3
 First land plants
Cambrian
542.0
 Trilobites dominant, First fish, NO LAND animals
4568
 O2 rises due to photosynthetic organisms
Earliest Life 3.5 BYA
 Source:
Time Scale Continued

7. Blank Time Scale Era Period Epoch Began (millions of years)
Characteristics from geologic and fossil evidence
Connecticut Valley Geological Events
Cenozoic
Recent
Life /
Age of Mammals
Quaternary
Holocene
 Rise of civilization and agriculture. 
Pleistocene
1.806
 Modern humans appear. 4 major glaciations cause rapid shifts in ecological communities.
Neogene
Pliocene
5.332
 First hominids appear.
Miocene
23.03
 Dogs & bears appear
Paleogene
Oligocene
33.9
 Worldwide tropical rainforests.
Eocene
55.8
 Early mammals abundant
Paleocene
65.5
 First primates
Mesozoic
Middle Life / Age of Reptiles
Cretateous
145.5
 Mass extinction of most large animals
Jurassic
199.6
 Dinosaurs dominate & 1st birds
Triassic
251.0
 Origin of mammals, dinosaurs 
Blank Time Scale

8. Extinction Events Extinction Events
Era
Period
Began (millions of years)
Characteristics from geologic and fossil evidence
Paleozoic
Ancient Life
Permian
299.0
 Major extinction of 95% of marine species
Pennsylvanian
318.1
 First reptiles & extensive c.s.f.
Mississipian
359.2
 First coal swamp forests
Devonian
416.0
 First amphibians.
Silurian
443.7
 large reefs appear
Ordovician
488.3
 First land plants
Cambrian
542.0
 Trilobites dominant, First fish, NO LAND animals
4568
 O2 rises due to photosynthetic organisms
Earliest Life 3.5 BYA
 Source:
endangeredspeciesinternational.org
Extinction
Events
Extinction Events
Late Devonian extinction – cause unknown , warm species most impact
Ordovician-Silurian extinction
Sea level drop followed by sea level rise
25% marine life

9. Extinction Events (more)
Era
Period
Epoch
Began (millions of years)
Characteristics from geologic and fossil evidence
Cenozoic
Recent
Life /
Age of Mammals
Quaternary
Holocene
 Rise of civilization and agriculture. 
Pleistocene
1.806
 Modern humans appear. 4 major glaciations cause rapid shifts in ecological communities.
Neogene
Pliocene
5.332
 First hominids appear.
Miocene
23.03
 Dogs & bears appear
Paleogene
Oligocene
33.9
 Worldwide tropical rainforests.
Eocene
55.8
 Early mammals abundant
Paleocene
65.5
 First primates
Mesozoic
Middle Life / Age of Reptiles
Cretateous
145.5
 Mass extinction of most large animals
Jurassic
199.6
 Dinosaurs dominate & 1st birds
Triassic
251.0
 Origin of mammals, dinosaurs 
Extinction Events (more)
Cretaceous-Tertiary – asteroid impact in Yucatan
End of Triassic due to volcanism associated with break-up of Pangea
Permian-Triassic
Worst mass extinction, 95% of all life, comet/asteroid was cause

10. Recent period
The most recent period is the Quaternary

11. Epoch
On the geologic time scale, the smallest unit of time is called an epoch - longer than an age and shorter than a period.

12. Phanerozoic Eon
Eon
4 total, half a billion years or more
Era
10 total, several hundred million years
Period
Epoch
tens of millions of years
Age
millions of years
The Phanerozoic Eon includes the Paleozoic, Mesozoic, and Cenozoic Eras

13. Eons
The Archean and Proterozoic are examples of eons

14. Cloudina, the earliest known calcium carbonate shell-bearing fossil.
End of the Precambrian
The end of the Precambrian is marked by the appearance of organisms with hard parts.
Cloudina, the earliest known calcium carbonate shell-bearing fossil.

15. Units of geologic time
Era
Period
Epoch
Began (MYA)
Cenozoic
Quaternary
Holocene
0.011
Pleistocene
1.8
Tertiary
Pliocene
5.3
Miocene
23.8
Oligocene
33.7
Eocene
54.8
Paleocene 65
Mesozoic
Cretaceous
144
Jurassic
206
Triassic
248
Paleozoic
Permian
290
Carboniferous Pennsylvanian
323
Carboniferous Mississippian
354
Devonian
417
Silurian
443
Ordovician
490
Cambrian
540
Precambrian time
4600
Adapted from Modern Earth Science, 2002, Holt, Rinehart and Winston
Units of geologic time in order from shortest to longest
epoch, period, era, eon

16. Periods
Periods are defined by the abundance or extinction of life-forms.

17. Eras vs. Periods Both are units of time on the geologic time scale.
are longer spans of time, measured in hundreds of millions to billions of years. They are defined by differences in life-forms found in rocks.
are usually measured in terms of tens of millions of years to hundreds of millions of years. They are defined by the life-forms that were abundant or became extinct during the time in which specific rocks were deposited.

18. Break + Quiz

19. Part 2 Objectives
Apply the principles for determining relative age to interpret rock sequences.
Describe an unconformity and how it formed within the rock record.

20. Oldest rock layer
The oldest rock layer in an undisturbed rock sequence occurs at the bottom of the sequence

21. The Principle of Superposition
The principle of superposition states that, in an undisturbed sequence, the oldest rocks are at the bottom of the sequence and successive layers are younger than those below them.

22. Cross-cutting Relationships
You can use the principle of cross-cutting relationships to infer that a fault or an intrusion is younger than the rock it cuts across.

23. Correlation
The matching of rock layers from one geographic area with those of another area is known as correlation.

24. Inferences and rock layers

25. Uniformitarianism
The principle of uniformitarianism states that the processes occurring today have been occurring on Earth since it formed. However, the rate, intensity, and scale with which these processes occur have changed.

26. Unconformity
When part of the rock record is destroyed, the erosional gap that forms is an unconformity.

27. Angular Unconformity
The gap in the rock record that occurs between folded or uplifted rock layers and a sedimentary rock layer on top of them is called an angular unconformity.

28. Nonconformity
A buried erosional surface between a nonsedimentary rock and a sedimentary rock is called a nonconformity.

29. Part 3 Objectives
Explain the several different methods used by scientists to determine absolute age.
Describe how objects are dated by the use of certain radioactive elements.
Explain how annual tree rings and glacial varves are used to date geological events.

30. Half Lives for Radioactive Elements
½ Life
The amount of time it takes for one-half of the original amount of an isotope to decay is known as its half-life.
Radioactive Parent
Stable Daughter
Half life
Potassium 40
Argon 40
1.25 billion yrs
Rubidium 87
Strontium 87
48.8 billion yrs
Thorium 232
Lead 208
14 billion years
Uranium 235
Lead 207
704 million years
Uranium 238
Lead 206
4.47 billion years
Carbon 14
Nitrogen 14
5730 years
½ Life Practice Sheet

31. Absolute dating
Radiometric dating is used to determine the absolute age of a rock

32. Key Beds
A key bed contains distinctive material that geologists can easily recognize in the rock record and use as a time marker.

33. Contrast relative-age dating and absolute-age dating.
Relative-age dating places the ages of rocks and the events that formed them in order, without exact dates. This is done by comparing one event with another or one rock with another rock.
In contrast, absolute-age dating determines the actual age of a rock, a fossil, or an object. This is done through radiometric dating, a process that determines the ratio of parent material to daughter product in a given sample of rock or fossil.

34. Part 4 Objectives Define fossil.
Explain several methods by which fossils can be preserved.
Describe the characteristics of an index fossil.
Discuss how fossils can be used to interpret Earth’s past physical and environmental history.

35. Fossils 
Fossils are the remains or evidence of once-living plants or animals. They provide clues about Earth’s past environmental conditions and evolutionary changes in organisms over time. They also help to correlate rock layers from one area to another.

36. Fossils (continued)
Fossil insects preserved in hardened tree sap are called amber.

37. Fossils (continued)
Molds, casts, coprolites, and petrified wood are all example of fossils

38. Fossils - original preservation
Mummified animals found in dry caves can be examples of fossils with original preservation.

39. Fossils - original preservation
Fossil insects can be found imbedded in amber, the hardened sap of prehistoric trees.
An insect imbedded in amber is an example of a fossil with original preservation.

40. Fossils (altered)
An example of a fossil with altered hard parts includes petrified wood

41. Trace Fossils
An example of a trace fossil includes worm trails.

42. Permineralization
In the process of permineralization, pore spaces within an organism’s shell are filled in with mineral substances.

43. Fossils - casts
A cast forms when the hollowed-out impression of a fossil organism becomes filled with minerals or sediment.

44. Fossils - molds
When the original parts of an organism in a sedimentary rock are weathered and eroded, a hollowed-out impression called a mold forms.

45. Index fossils
Index fossils are useful to geologists if the fossils have lived over a short period of time

46. Index vs. Trace Fossils 
Both are similar in that they are types of fossils.
Index fossils
Trace fossils
are the remains of organisms that can be used by geologists to correlate rock layers over large geographic areas or to date rock layers.
are not remains but indirect evidence of organisms, such as imprints, trails, and burrows.

47. Evolution
The adaptation of life-forms to changes in the environment is known as evolution.
A process by which (generations of) organisms adapt to changes in their environments.