Objectives

1
Objectives
The Early Paleozoic

• 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
Continental Setting
The Early Paleozoic

• 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 todays hurricanes, contributed to erosion
  and formation of sandy beaches. Corals thrived in
  the warm ocean waters and ultimately contributed
  to the formation of limestone.

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Continental Setting
The Early Paleozoic

• Characteristic Sediments

• A characteristic pattern of sandstone-shale-limest
  one 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
Changes in Sea Level
The Early Paleozoic

• 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.

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Changes in Sea Level
The Early Paleozoic
8
Early Paleozoic Life
The Early Paleozoic

• 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.

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Section Assessment
The Early Paleozoic

• 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
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Section Assessment
The Early Paleozoic

• 2. Why is the beginning of the Cambrian Period
  sometimes called the Cambrian explosion?

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Section Assessment
The Early Paleozoic

• 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. ______ Durin
g the Cambrian Period, Laurentia was surrounded
by passive margins.
12
End of Section 1
13
Objectives
The Middle Paleozoic

• 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

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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.

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Sea Level Changes Again
The Middle Paleozoic

• Sea level rose during the Early Ordovician and,
  once again, a beach environment covered much of
  Laurentias 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.
  

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Sea Level Changes Again
The Middle Paleozoic
17
Sea Level Changes Again
The Middle Paleozoic

• The Great Lakes area of North America contains
  huge deposits of Silurian-aged evaporite
  minerals, including halite, anhydrite, and gypsum
  that are minedcommercially.

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Middle Paleozoic Tectonics
The Middle Paleozoic

• 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.
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Middle Paleozoic Tectonics
The Middle Paleozoic

• 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.

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Middle Paleozoic Tectonics
The Middle Paleozoic

• 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.

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Middle Paleozoic Tectonics
The Middle Paleozoic

• 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.

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Middle Paleozoic Tectonics
The Middle Paleozoic
23
Middle Paleozoic Life
The Middle Paleozoic

• 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.

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Middle Paleozoic Life
The Middle Paleozoic

• 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.

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Life Moves to Land
The Middle Paleozoic

• 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.

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Life Moves to Land
The Middle Paleozoic

• 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.

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Mass Extinctions
The Middle Paleozoic

• Two of the greatest extinction events in Earths
  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.

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Mass Extinctions
The Middle Paleozoic

• 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 Earths 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
Section Assessment
The Middle Paleozoic

• 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
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Section Assessment
The Middle Paleozoic

• 2. What two developments in plants allowed the
  widespread colonization of land?

31
Section Assessment
The Middle Paleozoic

• 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
The Late Paleozoic

• 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

• 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

• 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

• 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

• 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
Reefs and Evaporites
The Late Paleozoic

• 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

• 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

• 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
Late Paleozoic Life
The Late Paleozoic

• 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.

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Late Paleozoic Life
The Late Paleozoic

• 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.

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Late Paleozoic Life
The Late Paleozoic

• 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.

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The Permian Mass Extinction
The Late Paleozoic

• 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.

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The Permian Mass Extinction
The Late Paleozoic

• 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.

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Section Assessment
The Late Paleozoic

• 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
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Section Assessment
The Late Paleozoic

• 2. How does the Great Permian Reef Complex have
  modern commercial value?

50
Section Assessment
The Late Paleozoic

• 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 Main Ideas
Section 23.1 Study Guide

• 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 Main Ideas
Section 23.2 Study Guide

• 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.

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Section 23.3 Main Ideas
Section 23.3 Study Guide

• 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
Chronological Order
Chapter Assessment

• 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
Short Answer
Chapter Assessment

• 7. What is the process of overturning?

57
True or False
Chapter Assessment

• 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.

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Chapter 23 Images
Image Bank
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Chapter 23 Images
Image Bank
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Chapter 23 Images
Image Bank