Objectives

1. 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 marginis an edge of a continent, or margin, where there is no tectonic activity.

4. The Early Paleozoic Continental Setting 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. 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 B D C A 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?” The expression Cambrian “explosion” refers to the dramatic increase in the diversity and abundance of life-forms near the beginning of the Cambrian Period.

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. false true false true

12. End of Section 1

13. The Middle Paleozoic Objectives • 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. 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. The Middle Paleozoic Sea Level Changes Again

17. 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 minedcommercially.

18. 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. 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. 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. 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. 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. 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. 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 C B D A 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? The development of vascular tissue and the emergence of seeds 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. true false false true

32. End of Section 2

33. 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. • Gondwanawas 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. 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. 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. 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. 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. 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. 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. 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. 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 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 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 D B C 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? The pore spaces in Permian reefs and in the surrounding course-grained rocks are filled with oil, making these reefs important oil reservoirs. The thick salt deposits that formed behind the reefs have very low permeability, making them an excellent environment for the storage of nuclear waste.

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. false true false true