1. Objectives Vocabulary
The Early Paleozoic
Objectives
Describe the Cambrian paleogeography of Laurentia.
Discuss the concept of a passive margin.
Describe the Cambrian fauna.
Vocabulary
paleogeography
passive margin
transgression
regression
Burgess Shale

2. The Early Paleozoic
The Early Paleozoic
Clues from the Paleozoic Era help us to understand how the diversity of life developed.
The Paleozoic story explains how early life-forms moved from water to land, why the Appalachians exist, and why they contain the vast coal deposits that fueled the industrial revolution.

3. The Early Paleozoic
Continental Setting
Paleogeography is the ancient geographic setting of an area.
The supercontinent Rodinia was present at the end of the Proterozoic.
By the Cambrian, Laurentia had split off from Rodinia, was located near the equator, and was surrounded by ocean.
Throughout the Cambrian Period, there was no plate tectonic activity on Laurentia.
A passive margin is an edge of a continent, or margin, where there is no tectonic activity.

4. Continental Setting The Early Paleozoic
Laurentia was positioned at the equator during the Early Paleozoic. Strong tropical storms, much like today’s hurricanes, contributed to erosion and formation of sandy beaches. Corals thrived in the warm ocean waters and ultimately contributed to the formation of limestone.

5. Continental Setting Characteristic Sediments
The Early Paleozoic
Continental Setting
Characteristic Sediments
A characteristic pattern of sandstone-shale-limestone deposits formed that represents increasing water depth from the shore of a vast inland sea.
Large, sandy beaches formed along the shoreline, clay-sized sediments were deposited in slightly deeper water, and carbonate sediment accumulated in even deeper water.
Over time, the sandy beaches became sandstone, the clay-sized sediments compacted to form shale, and the carbonate sediment became limestone.

6. The Early Paleozoic
Changes in Sea Level
Any changes in sediments may indicate changes in sea level.
A transgression occurs when sea level rises and the shoreline moves further inland, resulting in deeper-water deposits overlying shallower-water deposits.
A regression occurs when sea level falls and causes the shoreline to move seaward, resulting in shallow-water deposits overlying deeper-water deposits.
As sea level rises or falls, sediments that are lateral to each other become stacked one on top of another.

7. The Early Paleozoic
Changes in Sea Level

8. The Early Paleozoic
Early Paleozoic Life
Organisms representing all but one of the major marine groups appeared during the Cambrian Period.
The development of mineralized skeletons or hard parts helps mark the beginning of the Cambrian period.
Burgess Shale in the Canadian Rocky Mountains is the source for some of the best fossilized Cambrian organisms.

9. The Early Paleozoic
Section Assessment
1. Match the following terms with their definitions.
___ paleogeography
___ passive margin
___ transgression
___ regression
A. shallow-water deposits overlying deeper-water deposits due to a falling sea level
B. a continental edge with no tectonic activity
C. deeper-water deposits overlying shallow-water deposits due to a rising sea level
D. the ancient geographic setting of an area

10. The Early Paleozoic
Section Assessment
2. Why is the beginning of the Cambrian Period sometimes called the Cambrian “explosion?”

11. The Early Paleozoic
Section Assessment
3. Identify whether the following statements are true or false.
______ By the Cambrian, Laurentia was connected to Rodinia.
______ Organisms representing all but one of the major marine groups appeared during the Cambrian.
______ Burgess Shale is located in the Appalachian Mountains.
______ During the Cambrian Period, Laurentia was surrounded by passive margins.

12. End of Section 1

13. Objectives Vocabulary Describe the Middle Paleozoic paleogeography.
Explain the concept of an active margin and the formation of a clastic wedge.
Describe the Middle Paleozoic fauna.
Define the concept of mass extinction.
Vocabulary
Taconic Orogeny
Caledonian Orogeny
Acadian Orogeny
Antler Orogeny
Paleozoic fauna
vascular plant
mass extinction

14. The Middle Paleozoic
The Middle Paleozoic
The passive margin that existed around Laurentia continued into the Early Ordovician Period.
The paleogeography of Laurentia was still equatorial, with the paleo-equator running from approximately modern-day New Mexico through Minnesota.

15. Sea Level Changes Again
The Middle Paleozoic
Sea Level Changes Again
Sea level rose during the Early Ordovician and, once again, a beach environment covered much of Laurentia’s margins.
The resulting sandstone is overlain by minor amounts of shale and by extensive limestone deposits that include the first corals that built organic reefs.
Organic reefs are structures composed of carbonate skeletons made by living organisms.
Reefs affect the environments in which they grow.

16. Sea Level Changes Again
The Middle Paleozoic
Sea Level Changes Again

17. Sea Level Changes Again
The Middle Paleozoic
Sea Level Changes Again
The Great Lakes area of North America contains huge deposits of Silurian-aged evaporite minerals, including halite, anhydrite, and gypsum that are mined commercially.

18. Middle Paleozoic Tectonics
The Middle Paleozoic
Middle Paleozoic Tectonics
During the Middle Ordovician, an ocean-continent collisional boundary, an active margin, developed in what is now eastern North America.
The Taconic Orogeny, a mountain-building event named for the Taconic Mountains of eastern New York State, occurred during the Middle Ordovician.

19. Middle Paleozoic Tectonics
The Middle Paleozoic
Middle Paleozoic Tectonics
We know that this Taconic Orogeny occurred because of:
the existence of angular unconformities.
the existence of lava flows, volcanic ash deposits, igneous intrusions, and regional metamorphic features that are Middle-to-Late Ordovician in age in present-day eastern North America.
the existence of a wedge of sediment, called a clastic wedge, that formed as the mountains from the Taconic Orogeny eroded.

20. Middle Paleozoic Tectonics
The Middle Paleozoic
Middle Paleozoic Tectonics
Orogenies and Deformation
Tectonism continued during the Late Silurian and into the Devonian when Laurentia collided with Baltica.
This collision joined Laurentia and Baltica into a larger continent known as Laurasia.

21. Middle Paleozoic Tectonics
The Middle Paleozoic
Middle Paleozoic Tectonics
Orogenies and Deformation
Caledonian Orogeny, the collisional tectonic event that occurred when Laurentia and Baltica collided, closed the ocean that had separated these two continents.
The Acadian Orogeny was the result of a microcontinent called Avalonia, which is now Newfoundland, colliding with the southeastern margin of Laurasia.
The Antler Orogeny was a collisional tectonic event during the Late Devonian, and into the early Mississippian, that affected the passive western margin of Laurentia.

22. Middle Paleozoic Tectonics
The Middle Paleozoic
Middle Paleozoic Tectonics

23. The Middle Paleozoic
Middle Paleozoic Life
The Middle Paleozoic seas were dominated by animals that are collectively called the Paleozoic fauna.
The animals that dominated the Cambrian seas were replaced during the Early Ordovician by a variety of new organisms.

24. The Middle Paleozoic
Middle Paleozoic Life
Corals deposit thin layers of carbonate, called growth lines, to their skeletons each day.
Corals indicate that Earth was rotating more rapidly during the Paleozoic and has been slowing ever since.

25. The Middle Paleozoic
Life Moves to Land
For the first time in the history of life on Earth, land was colonized during the Middle Paleozoic.
Fossilized plant parts and spores suggest that some form of land plant existed during the Late Ordovician.
Vascular plants have tissue for circulating water and nutrients through their stems and leaves.
The development of vascular tissue allowed plants to spread out on land.

26. Life Moves to Land New Plants Emerge
The Middle Paleozoic
Life Moves to Land
New Plants Emerge
By the Late Devonian, three important groups of vascular spore-bearing plants were living on land: ferns, sphenopsids, and lycopods.
During the Late Devonian, the seed ferns developed.
The most important aspect of these plants was the development of seeds, which allowed plants to spread out and colonize dry land.

27. The Middle Paleozoic
Mass Extinctions
Two of the greatest extinction events in Earth’s history occurred during the Middle Paleozoic.
A mass extinction is when an unusually large number of organisms becomes extinct over a relatively short period of geologic time.
The first mass extinction occurred at the end of the Ordovician Period when approximately 57 percent of all marine genera became extinct.
An episode of global cooling caused the extinction of many species that were adapted to warm environments.

28. Mass Extinctions Global Cooling and Overturning
The Middle Paleozoic
Mass Extinctions
Global Cooling and Overturning
A second mass extinction occurred during the late Devonian when approximately 50 percent of the marine genera were wiped out.
The cooling of Earth’s atmosphere may have caused a tremendous disturbance in the ocean system.
This disturbance created overturning, a process in which oxygen-poor, deep ocean water rises up, creating surface waters that contain little or no oxygen.

29. The Middle Paleozoic
Section Assessment
1. Match the following terms with their definitions.
___ Taconic Orogeny
___ Caledonian Orogeny
___ Acadian Orogeny
___ Antler Orogeny
A. collisional tectonic event that affected the passive western margin of Laurentia
B. collisional tectonic event that occurred when Laurentia and Baltica collided
C. a mountain-building event that occurred during the Middle Ordovician along what is now eastern North America
D. tectonic event resulting from Avalonia colliding with the southeastern margin of Laurasia

30. The Middle Paleozoic
Section Assessment
2. What two developments in plants allowed the widespread colonization of land?

31. The Middle Paleozoic
Section Assessment
3. Identify whether the following statements are true or false.
______ Global cooling led to a mass extinction during the late Devonian.
______ The equator ran through present-day Alaska during the Early Ordovician Period.
______ As Earth ages, the days are getting longer.
______ Large amounts of evaporites are found in the Great Lakes region.

32. End of Section 2

33. Objectives Vocabulary Describe the formation of Pangaea.
The Late Paleozoic
Objectives
Describe the formation of Pangaea.
Explain how cyclothems formed.
Identify the importance of amniote eggs.
Discuss the causes of the Late Permian mass extinction.
Vocabulary
Gondwana
cyclothem
Ouachita Orogeny
Ancestral Rockies
Alleghenian Orogeny
amniote egg

34. The Late Paleozoic
The Late Paleozoic
During the Late Paleozoic, the supercontinent Pangaea formed.
Gondwana was a large continent in the southern hemisphere that formed as a result of collisional events between South America, Africa, India, and Antarctica.

35. The Late Paleozoic
The Late Paleozoic

36. Sea Level and Deposition
The Late Paleozoic
Sea Level and Deposition
The Late Paleozoic began with Laurasia still covered by a shallow tropical sea.
Mississippian rocks throughout North America are predominantly limestone.
The end of the Mississippian was marked by a major regression of the sea.

37. Sea Level and Deposition
The Late Paleozoic
Sea Level and Deposition
The Pennsylvanian Period began with a slow transgression.
The Pennsylvanian and Permian rocks in central and eastern North America are predominantly river and delta deposits.
The Pennsylvanian Period is known for the coal deposits that accumulated in heavily vegetated lowland swamps.

38. Sea Level and Deposition
The Late Paleozoic
Sea Level and Deposition
Cyclothems
A cyclothem is a repeating cyclic pattern of sediments stacked one on top of another, as found in Pennsylvanian rocks in North America.
A regression is represented by layers of marine limestone and sandstone.
A transgression is represented by sandstone, clay, coal, shale, and marine limestone.

39. Sea Level and Deposition
The Late Paleozoic
Sea Level and Deposition
Cyclothems
In some parts of Laurentia, as many as 40 to 50 cyclothems were stacked one on top of the other.
Most geologists hypothesize that glaciation was responsible for the varying sea levels that caused the cyclothems.

40. The Late Paleozoic
Reefs and Evaporites
During the Permian, sponges and algae built a reef complex, known as the Great Permian Reef, in what is now western Texas, southeastern New Mexico, and northern Mexico.
The pore spaces in Permian reefs and in the surrounding coarse-grained rocks are filled with oil, making these reefs important oil reservoirs.
The thick salt deposits that also formed have very low permeability, making them an excellent environment for long-term storage of nuclear waste.

41. Continental Collisions and Mountain Building
The Late Paleozoic
Continental Collisions and Mountain Building
The Late Paleozoic was a time of active mountain building.
During the Ouachita Orogeny, Gondwana collided with the southeastern margin of Laurasia, forming the Ouachita Mountains of Arkansas and Oklahoma and the mountains in the Marathon area of West Texas.
The Ancestral Rockies were created during the Ouachita Orogeny as the collision was so intense that it caused the crust to uplift inland as far as present-day Colorado.

42. Continental Collisions and Mountain Building
The Late Paleozoic
Continental Collisions and Mountain Building
The Alleghenian Orogeny was the last of the three major mountain-building events to affect what is now eastern North America, and resulted in the formation of the Appalachian Mountains.
Pangaea had formed.

43. The Late Paleozoic
Late Paleozoic Life
The invertebrate marine organisms that flourished during the Middle Paleozoic continued to dominate the marine environment.
One group, the crinoids, became dominant during the Mississippian.

44. Late Paleozoic Life Changes in the Ocean
The Late Paleozoic
Late Paleozoic Life
Changes in the Ocean
Following the extinction of many fishes during the Late Devonian, sharks and other ray-finned fishes became more abundant.
Lobe-finned fishes appeared during the Late Devonian, but became more abundant during the Late Paleozoic.
The true ferns, sphenopsids, lycopods, and seed ferns had thoroughly invaded the swampy land of the Pennsylvanian, ultimately giving rise to the great coal swamps of the Pennsylvanian.
Swamps were a breeding ground for insects as well as plants.

45. Late Paleozoic Life Changes in the Ocean
The Late Paleozoic
Late Paleozoic Life
Changes in the Ocean
Amphibians, the top carnivores on the land, had to remain close to water because their eggs had no protective coating to prevent them from drying out.
Reptiles that evolved from the early amphibians during the Late Mississippian developed a new type of egg.
The amniote egg has a shell that protects the embryo, which is surrounded by a liquid-filled sac that contains a food sac and a waste sac.
During the Permian, reptiles became abundant on land and displaced the amphibians as the top land carnivores.

46. The Permian Mass Extinction
The Late Paleozoic
The Permian Mass Extinction
The largest mass extinction in the history of life on Earth defines the end of the Paleozoic Era.
The Permo-Triassic Extinction Event marks the end of nearly 95 percent of all species, and affected terrestrial as well as marine animals.
More than 65 percent of the amphibians and reptiles did not survive, nor did almost one-third of all insects.

47. The Permian Mass Extinction
The Late Paleozoic
The Permian Mass Extinction
A Major Marine Regression
A major marine regression is one possible cause of the Permo-Triassic Extinction Event.
Now, as then, most marine animals live in the relatively shallow water called the continental shelf.
During regression, the continental shelf became very narrow, leaving little space for marine animals to live.
Life on Earth was irrevocably changed at the end of the Paleozoic.

48. The Late Paleozoic
Section Assessment
1. Match the following terms with their definitions.
___ Gondwana
___ cyclothem
___ Ouachita Orogeny
___ Alleghenian Orogeny
A. large supercontinent that was located in the southern hemisphere
B. mountain-building event that was caused when Gondwana collided with the southeastern margin of Laurasia
C. the last of the three major mountain-building events to affect what is now eastern North America
D. a repeating cyclic pattern of sediments stacked one on top of another

49. The Late Paleozoic
Section Assessment
2. How does the Great Permian Reef Complex have modern commercial value?

50. The Late Paleozoic
Section Assessment
3. Identify whether the following statements are true or false.
______ Trilobites became extinct during the Ouachita Orogeny.
______ Reptiles developed from the amniote egg.
______ The Pennsylvanian Period is known for its extensive deposits of limestone.
______ In some parts of Laurentia, as many as 50 cyclothems were stacked on top of each other.

51. End of Section 3

52. Section 23.1 Study Guide
Section 23.1 Main Ideas
The ancient North American continent of Laurentia was located near the equator and surrounded by ocean during the Cambrian Period. A shallow sea covered most of Laurentia.
Laurentia was completely surrounded by passive margins throughout the entire Cambrian Period.
Many new organisms developed during the Cambrian explosion. Fossils of trilobites and articulate brachiopods are particularly common in Cambrian rocks.
When environments change position laterally due to changes in sea level, adjacent depositional facies overlie each other in vertical succession.

53. Section 23.2 Study Guide
Section 23.2 Main Ideas
High evaporation rates in lagoon settings cause the water to become oversaturated with calcium and sodium. These elements combine with other elements or compounds in the water and precipitate out of solution as the evaporite minerals.
Clastic wedges provide evidence for orogenic events.
The seas were dominated by articulate brachiopods, corals, mollusks, bryozoans, crinoids, graptolites and conodonts. Fishes were the top predators of the seas during the Devonian. Ferns, sphenopsids, and lycopods covered the landscape by the Late Devonian.
Two mass extinctions occurred. A mass extinction occurs when an unusually large number of organisms becomes extinct over a relatively short period of geologic time.

54. Section 23.3 Study Guide
Section 23.3 Main Ideas
Pangaea formed as Laurasia (North America + Europe) collided with Gondwana (South America, Africa, India, Australia and Antarctica).
Cyclothems consist of transgressive and regressive rock sequences stacked one on top of another. They represent cycles of glacial-interglacial periods.
Seeds evolved and allowed plants to colonize dry land. The amniote egg evolved and allowed reptiles to colonize dry land.
One possible cause of the Permo-Triassic Extinction Event was regression. Marine habitats around Pangaea shrank. Feedback from this event caused global warming, which affected organisms on land as well as in the sea.

55. Chapter Assessment
Chronological Order
6. Number the following periods of the Paleozoic era in the order that they occurred.
___ Silurian Period
___ Devonian Period
___ Cambrian Period
___ Pennsylvanian Period
___ Ordovician Period
___ Mississippian Period
___ Permian Period

56. Chapter Assessment
Short Answer
7. What is the process of overturning?

57. Chapter Assessment
True or False
8. Identify whether the following statements are true or false.
______ The Late Ordovician mass extinction may have been caused by an episode of global cooling.
______ The Antler Orogeny primarily affected the southeastern part of Laurasia.
______ Amphibians were the first to have amniotic eggs.
______ Throughout the Cambrian, there was no plate tectonic activity on Laurentia.
______ Paleozoic fauna refers to animals that dominated the Cambrian seas.

58. Image Bank
Chapter 23 Images

59. Image Bank
Chapter 23 Images

60. Image Bank
Chapter 23 Images