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180 Chapter 21 The Geology of the Paleozoic Era GUIDED STUDY The text chapter should be studied one section at a time. Before you read, preview each section by skimming it, noting headings and boldface items. Then read the appropriate section objectives from the following outline. Keep these objectives in mind and, as you read the chapter section, search for the information that will enable you to meet each objective. Once you have finished a section, write out answers for its objectives. The Divisions of the Paleozoic (pp. 425-427) 1. Explain how the base of the Cambrian System has changed from its original definition. 2. Explain how the Carboniferous System relates to the Mississippian and Pennsylvanian systems of the United States. A Global Perspective (pp. 427-432) 5. Explain the reasons for extreme aridity on the supercontinent of Pangaea during the Late Permian Period. North America in the Paleozoic (pp. 432-447) 6. Discus the events that built the Taconic Mountains during the early Paleozoic, and the landforms that resulted from their erosion. 7. What landmasses were involved in the Caledonian orogeny? 8. Discuss the origin and significance of the Catskill clastic wedge. 3. Describe the formation of the massive continent of Gondwana. 4. Discuss the events that led to the assembly of the supercontinent of Pangaea. 9. List the provinces of the Appalachian mountain belt, and the deformation experienced by each. Copyright © Houghton Mifflin Company. All rights reserved. 181 10. Describe the tectonic events associated with the Antler orogeny. The Divisions of the Paleozoic (pp. 425-427) 4. The time of “ancient life” has been named the_______________ Era, which is the firt era of the Phanerozoic Eon. 5. The first (lowest) appearance of easily visible fossils marked the beginning of the _____________ 11. List the four transgressive-regressive sequences that migrated across the craton during the Paleozoic. What type of boundary exists at the top of each? Period. Its boundary has subsequently been lowered to include both small shelly fossils and the occurrence of complex, branching _____ ________. 6. The overlying _______________ System was named for a tribe of ancient Welsh inhabitants. 7. The next time interval is the __________ Period, also named for ancient Welsh peoples. 8. The geologic time period named for Devon County 12. Discuss the origin, sedimentary sequences, and economic products associated with cyclic sedimentation of the Pennsylvanian Period. in southern England is the __________ Period. 9. The world outside the United States recognizes the _________________ System, named for the coalbearing strata of England. 10. In the United States, strata that are roughly time equivalent to the lower part of this sequence are assigned to the _______________ Period, whereas strata in the upper part belong to the CHAPTER REVIEW When you have finished reading the chapter, work through the material that follows to review it. Complete the sentences. As you proceed, evaluate your performance for each section by consulting the answers on pages 188. Do not continue with the next section until you understand each answer. If you need to, review or reread the appropriate section in the textbook before continuing. Introduction (p. 425) 1. The Paleozoic Era began with a continuation of the breakup of the supercontinent________________. 2. Quart-rich sands began the _______________ that eventually covered most of the North American craton in the Ordovician Period. 3. A series of continental collisions during the Paleozoic culminated in the formation of the supercontinent called _____________. Copyright © Houghton Mifflin Company. All rights reserved. _________________ Period. 11. The _______________ Period is named for a city in central Russia. Its end marks a time of the greatest extinction in all of Earth history. A Global Perspective (pp. 427-432) 12. During the early Cambrian, landmasses containing present-day South America, Africa, India Australia, and Antarctica collided together to form the massive continent of _______________. 13. North America, Greenland, and northern Great Britain formed the continent of ____________. 14. _________, _________, and _________________ were the other major Cambrian landmasses. 15. The_________ ________ separated Laurentia from Baltica. 16. The third step in the Wilson cycle is ___________. 182 17. The merging of Laurentia and Baltica formed the larger continent of __________. 18. The northern margin of Gondwana merged with the southern margin of Laurentia during the ____________ ________. 19. The continents of Siberia and Kazakhstania 29. The large size, interruption of equatorial oceanic circulation, numerous mountain ranges, and cold coastal currents produced a(n)_____ __________ on Pangaea. 30. Warm temperatures contribute to the dryness of a region by inhibiting both coal formation and collided during the Pennsylvanian to form the ______________. Both processes conserve carbon ________ _______________ of central Asia. dioxide, which as a greenhouse gas heats up the 20. The collision of Baltica with Kazakhstania during atmosphere even more. the Permian caused the __________ ___________ North America in the Paleozoic (pp. 432-447) and the suturing of these two continents. 31. Deposition of sediment over much of the North 21. Pangaea was formed by the collision of Laurasia with Gondwana. The single ocean surrounding this continent from pole to pole was called _____________. 22. At the beginning of the Paleozoic, most major continents were located near the__________, which promoted warm climates. 23. Unrestricted circulation of oceanic waters between the poles and the tropics produces polar regions that are _________. 24. The warm, epeiric seas of the early Paleozoic were ideal for the formation of ______________ 25. During the Ordovician Period, Gondwana drifted over the ______ ______, resulting in the formation of large glaciers and a worldwide drop in ____ ______. 26. Gondwanan glaciation is indicated by deposits of __________ , and bedrock with glacial _____________. 27. Periods of late Paleozoic glaciation involve the balance of ________ ___________ in the atmosphere. 28. Both limestone deposition and periods of ______ _________ remove carbon dioxide from the American craton built the ________________ ___________. 32. Deformation of the eastern margin of North America throughout the Paleozoic built the _____________ ____________. 33. Small microcontinents or displaced terranes collide or accrete to the continental margin in a process called _________. 34. Mountains resulting from continental collisions were quickly eroded, forming thick _________ ___________. 35. The collision of North America with the Avalonia terrane occurred during the _______ ________ of Middle Ordovician age. 36. Erosion of the Taconic Mountains during the Late Ordovician and Early Silurian periods produced a thick sediment deposit called the______________ ______ _________. 37. The collision of Laurentia and Baltica occurred during the ____________ ________of Late Silurian to Early Devonian age. 38. The suturing of Laurentia with ________ formed the continent of Laurasia. 39. Erosion of the Caledonian Mountains produced a atmosphere, possibly triggering episodes of thick clastic wedge known in England as the _____ glaciation. Volcanic activity from rifting and ____ ____________. subduction, returns carbon dioxide to the atmosphere. Copyright © Houghton Mifflin Company. All rights reserved. 183 40. In the Early to Middle Devonian, the remainder of Avalonia docked with Laurasia during the________ _________. 41. The erosion of the Acadian Mountains formed a massive sedimentary deposit known as the________ ________ _________. 42. The Catskill Mountains of New York were formed by sediments eroded from the Acadian mountains, and stand as a prominent tableland because of their resistant sandstones and ________________. 43. The Late Paleozoic collision between Laurasia and Gondwana is called the ______________ __________. 44. Allegeheny deformation was different in each of three distinct structural provinces. In the __________ province, rocks were metamorphosed and intruded because of their proximity to the collision. 54. The top of such a sequence is defined by the occurrence of a widespread, erosional ______________. 55. The first cratonic sequence is called the _____ ___________. It covered most of North America with shallow seas. 56. The basal rock formation of the _____________ __________ is the St. Peter Sandstone. 57. Deposits of the __________ ___________ consist mainly of widespread, platform carbonates. 58. Erosion of tectonic highlands during the _________ __________ produced mainly terrestrial and marginal marine deposits. 59. Final regression at the end of the Permian left continental conditions across the entire _______. 60. Sedimentary sequences that contain an orderly, repetitive alternation of depositional environments are called _____________. 61. The pattern of deposition in an individual cyclothem results from _____________ and ____________. 62. Burial of vegetation on marshy coastal plains by marine sediments resulted in the production of Pennsylvanian _______. 63. The frequency of cyclothems suggests an individual cycle represents about ________years. 64. The cause of these cycles appears to be the growing and shrinking of____ ________ in Gondwana. 45. In the ______ _______ province, Late Proterozoic rocks were thrust cratonward along huge faults. 46. In the _________ ____ _______ province, strong folding and faulting occurred at the surface, while little deformation occurred at depth. 47. Late Paleozoic suturing of Gondwana and Laurasia along the southern margin of North America and PRACTICE TESTS After you thoroughly understand the correct answers of the Chapter Review, answer the following questions and check them with the answers on pages 188-189. If your answer is incorrect, consult the appropriate pages of the text (in parentheses following the correct answer). Multiple Choice Questions the northern margin of South America occurred in the _________ _________. 48. For most of the Paleozoic, the western portion of North America was a _______ ______. 49. Subduction between the Klamath arc and the western margin of North America resulted in their collision by Late Devonian times, an event called the _______ ________. 50. Deep-ocean sediments between the arc and the continent were _______ eastward over the continental shelf as much as 100 miles. 51. Uplift of crustal blocks along high-angle faults in the cratonic interior formed the _______ ________ 52. The stratigraphic record of North America contains a series of transgressive-regressive cycles that are called ________ ___________. 53. The base of each transgressive sequence is indicated by the deposition of ________ _______. Copyright © Houghton Mifflin Company. All rights reserved. Circle your answers to the following questions. 1. During the early Paleozoic, tropical lands include: a. Greenland. b. India. c. Africa. d. South America. 2. The appearance of easily visible fossils defines the beginning of the: a. Precambrian interval. b. Paleozoic Era. c. Mesozoic Era. d. Cenozoic Era. 3. The system that was described from southern England was the: a. Cambrian System. b. Ordovician System. c. Silurian System. 184 d. Devonian System. 4. The system described from central Russia was the: a. Carboniferous System. b. Permian System. c. Pennsylvanian System. d. Mississippian System. 5. The largest early Paleozoic continent was called: a. Siberia. b. Laurentia. c. Gondwana. d. Baltica. 6. Laurentia and Baltica were separated by the: a. Atlantic Ocean. b. Iapetus Ocean. c. Pacific Ocean. d. Panthalassa Ocean. 7. Laurentia and Baltica were soon joined to form: a. Asia. b. Gondwana. c. Pangaea. d. Lauraisa. 8. The Late Paleozoic collision between Baltica and Gondwana occurred in the: a. Hercynian orogeny. b. Uralian orogeny. c. Altai orogeny. d. None of the above. 9. At the end of the Permian Period, the single ocean surrounding Pangaea was called the: a. Iapetus Ocean. b. Pacific Ocean. c. Panthalassa Ocean. d. Atlantic Ocean. 10. Paleozoic ice ages resulted from: a. large landmasses located in the southern polar region. b. removal of carbon dioxide from limestone formation. c. removal of carbon dioxide from coal formation. d. All of the above. 11. Extreme aridity in the late Permian Period resulted from: a. a single large, wide landmass extending from pole to pole. b. removal of carbon dioxide from limestone formation. c. removal of carbon dioxide from coal formation. d. All of the above. 12. The Appalachian and Ouachita mountains were formed during the Paleozoic as a result of: a. continental rifting. b. continental collisions. c. continental drifting. d. passive margin deposition. 13. In the Taconic orogeny, Laurentia collided with: a. Baltica. b. Siberia. c. Avalonia. d. Gondwana. 14. The Queenston clastic wedge was derived from erosion of which mountains? a. Taconic c. Caledonian b. Acadian d. Rockies 15. The collision and suturing of Baltica and Laurentia occurred during this orogeny: a. Taconic orogeny. b. Caledinian orogeny. c. Acadian orogeny. d. Hercynian orogeny. 16. The Catskill clastic wedge was derived from the erosion of which mountains? a. Taconic b. Rockies c. Catskill d. Acadian 17. The environment of deposition represented by the much of the Catskill clastic wedge was: a. deep marine turbidites. b. shallow marine shelf. c. broad alluvial plain and floodplain. d. volcanic highlands. 18. Deformation during the Allegeheny orogeny was most severe in which tectonic province? a. Piedmont province b. Blue Ridge province c. Valley and Ridge province d. Plateau province 19. The Ouachita orogeny of Late Paleozoic age resulted from collision of the southern margin of North America with the northern margin of: a. Africa. b. South America. c. Siberia. d. Asia. 20. Western North America during the early Paleozoic experienced: a. continental collision. b. continental rifting. Copyright © Houghton Mifflin Company. All rights reserved. 185 c. subduction. d. sedimentation on a passive margin. True or False Items Write true or false on the line in front of each statement. 21. Accretion of the Klamath arc onto the western margin of North America was a result of the: a. Acadian orogeny. b. Antler orogeny. c. Klamath orogeny. d. Taconic orogeny. 22. The Ancestral Rockies were formed from highangle faults that relieved stress caused by the: a. Allegeheny orogeny. b. Antler orogeny. c. Ouachita orogeny. d. Acadian orogeny. 23. Erosion of the Ancestral Rockies produced deposition of great thicknesses of feldspar-rich sands and gravels, indicating that these mountains were composed of: a. basaltic lavas. b. plutonic granites. c. shallow-water limestones. d. glacial tillites. 24. In the four trangressive-regressive sequences that can be traced across the North American initial sedimentary layer of each sequence is composed craton, the of: a. quartz-rich sands. b. lime muds. c. organic-rich clays. d. glacial tills. 25. The top of each transgressive-regressive sequence is represented by: a. a volcanic ash layer. b. quartz-rich sands. c. a flow of basaltic lava. d. an erosional surface or unconformity. 26. The transgressive phase of each cratonic sequence covered most of North America except for a part of the Canadian Shield and the: a. Rocky Mountains. b. Appalachian Mountains. c. Transcontinental Arch. d. Sierra Nevada. 27. The major energy resource produced from Pennsylvanian cyclothem deposition is: a. natural gas b. coal. c. oil. d. tar sands. Copyright © Houghton Mifflin Company. All rights reserved. _____ 1. The world of the very early Paleozoic Era was already well populated with plants and animals similar to those of today. _____ 2. The Cambrian System includes all of the rocks deposited during the Cambrian Period. _____ 3. The last Paleozoic system is the Pennsylvanian System. _____ 4. The massive continent of Gondwana was already assembled before the beginning of the Paleozoic Era. _____ 5. The most important step in the assembly of Pangaea was the suturing of Laurasia with Gondwana. _____ 6. Siberia and Kazakhstania were the first continents to be joined together to eventually form Pangaea. _____ 7. Paleozoic ice ages were restricted to the northern parts of Pangaea. _____ 8. The Late Permian warmth resulted from the natural burning of coal deposits formed earlier in the Pennsylvanian Period. _____ 9. The collisions that built Pangaea were responsible for building the Appalachian and Ouachita mountains of North America. _____ 10. The closure of the Iapetus Ocean came about by the suturing of several terranes to the eastern margin of North America. _____ 11. Sediments eroded from the Taconic Mountains filled the Appalachian forelandbasin as the Catskill clastic wedge. _____ 12. The Blue Ridge structural province is famous for enormous thrust faults. _____ 13. Tectonic activity in Western North America was already present in the Cambrian Period. _____ 14. Cratonic sequences end with an erosional surface. _____ 15. The Sauk sequence begins with Cambrian sandstones. _____ 16. The Tapeats Sandstone is oldest in the eastern part of the Grand Canyon. _____ 17. The base of the Tippecanoe sequence in the midwestern United States begins with the St. Peter Sandstone. _____ 18. Evaporite deposition occurred in the interior of the Michigan basin during the Kaskaskia sequence. _____ 19. Final transgression in the Late Permian resulted in widespread deposition of continental redbeds in the southwestern United States. _____ 20. Coal formation occurs during the regressive phase of cyclothem deposition. 186 Essay Questions Write a brief essay on a separate sheet of paper answering each of the following questions. 1. List and describe the tectonic events responsible for the assembly of Pangaea. 2. List the structural provinces of the Appalachian Mountains, and describe the tectonic events that occurred in each. 3. Explain the concept of a cratonic sequence, and list the succession of sediments encountered. 4. What is a cyclothem, and what events were responsible for their formation? CHALLENGE TEST 8. During the Hercynian orogeny, the northern portion of Gondwana converged with _________ _______. 9. The Uralian orogeny brought together ________ and ________________ as the final event in the assembly of Pangaea. 10. The warm ______ seas of the early Paleozoic were ideal for limestone deposition. 11. Burial of organic matter as coal removes carbon dioxide from the atmosphere, triggering ______ ____________. 12. Aridity in the Late Permian served increase temperatures, because a lack of weathering and coal Answer these questions the day before an exam as a final check on your understanding of the chapter’s terms and concepts. Check your responses with the answers on pages 189-190. If your answer is incorrect, consult the appropriate pages of the text. formation on land left excess ________ _______ to buildup in the atmosphere and raise global temperatures. 13. As the continental collisions of North America with Completion Fill in the correct answers. 1. During the very early Paleozoic, ______________, Avalonia and Baltica occurred, the building of the ________________ _____________ began. 14. Sediments shed from both the Taconic and Acadian _______________, and ____________________, mountains were deposited westward as clastic were located in the tropical latitudes. wedges in the Appalachian ______________. 2. The Paleozoic Era began with the ___________ of Rodinia, and ended with the ___________ of Pangaea. 3. The Paleozoic Era was originally defined by the first appearance of easily visible _____________. 4. The Mississippian System was defined from exposures in the______________ ______ _____ 15. The Allegeheny orogeny was the climactic event in the mountain-building of the Appalachians, when _____________ collided with Gondwana. 16. The Ancestral Rockies formed as a byproduct of stresses from the __________ orogeny. 17. Pennsylvanian coal formation occurred primarily on the __________ half of the North American craton. Multiple-Choice Questions and the Pennsylvanian System from exposures in _______________. 5. East Gondwana contained the modern continents of__________ and _______ ____________. 6. The Iapetus Ocean separated __________ from ______________. 7. Laurasia and Gondwana were joined together in the Late Paleozoic by collision between the eastern Circle the correct answer. 1. At the beginning of the Paleozoic, the Wilson cycle in North America was: a. continental collision. c. continental drifting. b. continental rifting. d. subduction. 2. The major divisions in the geologic time scale were originally defined by: a. major tectonic events. c. sea level change. b. major climate events. d. fossil record change. margin of North America and the northwestern margin of _________. 3. The Carboniferous System of England was named for strata that were: a. iron-bearing. c. fossil-bearing. Copyright © Houghton Mifflin Company. All rights reserved. 187 b. diamond-bearing d. coal-bearing. 4. This geologic Period experienced the greatest episode of biologic extinction in Earth History: a. Devonian. c. Permian. b. Mississippian. d. Pennsylvanian. 5. At the beginning of the Paleozoic Era, Rodinia had fragmented into: a. two continents. c. four continents. b. three continents. d. six continents. 6. At the end of the Paleozoic Era, tectonic activity had assembled: a. two continents. c. four continents. b. one continent. d. six continents. 7. The Ural Mountains of Russia formed in the: a. Ordovician Period. c. Permian Period. b. Silurian Period. d. Devonian Period. 8. Sea level rise in the Cambrian was a result of: a. accelerated activity at mid-ocean ridges. b. melting of ice sheets. c. building of ice sheets. d. erosion of mountains formed by continental collisions. 9. The position of Pangaea astride the equator in Late Permian time drastically affected climate by: a. controlling oceanic circulation. b. melting southern ice sheets. c. building northern ice sheets. d. building equatorial ice sheets. 10. Tectonic activity on the craton of North America involved: a. mountain-building along the eastern margin. b. mountain-building along the western margin. c. sediment deposition over the central area. d. all of the above. 11. The Taconic Mountains were formed during the Early Paleozoic as a result of: a. continental rifting. b. continental collisions. c. continental drifting. d. microcontinent accretion. 12. In the Acadian orogeny, Laurasia collided with: a. Baltica. b. Siberia. c. the remnants of Avalonia. d. Gondwana. 13. Thickness of the Catskill clastic wedge is estimated to be: a. 4000 meters. c. 1000 kilometers. Copyright © Houghton Mifflin Company. All rights reserved. b. 9000 meters. d. 2000 kilometers. 14. The orogeny with the greatest extent of deformation is: a. Taconic. b. Acadian. c. Caledonian. d. Allegeheny. 15. The Appalachian structural province that experienced the least deformation during the Allegheney orogeny was the: a. Piedmont. c. Plateau. b. Blue Ridge. d. Valley and Ridge. True or False Items Write true or false on the line in front of each statement. _____ 1. Four major transgressions and regressions occurred in North America during the Paleozoic Era. _____ 2. The Mississippian System is not recognized in the United States. _____ 3. The opening of the Iapetus Ocean in theEarly Paleozoic began the formation of the Appalachian mountain belt. _____ 4. The Ural Mountains today form the physiographic boundary between Europe and Asia. _____ 5. Pangaea was surrounded by a single ocean called Tethys. _____ 6. Gondwana covered the South Pole during the Ordovician Period. _____ 7. Widespread glaciation causes carbon dioxide levels to drop. _____ 8. The interior of Pangaea was dry during the Late Permian age. _____ 9. The Ouachita Mountains formed along the southern margin of North America. _____10. The Taconic orogeny involved the collision between Laurasia and Baltica. _____11. Erosion of the Caledonian orogen produced the clastic wedge called the Old Red Sandstone. _____12. Redbeds of the Catskill clastic wedge represent arid desert environments. _____13. The Piedmont structural province is famous for enormous thrust faults. _____14. The Ancestral Rockies represent accretion of a volcanic arc onto the western margin of North America. 188 ANSWERS CHAPTER REVIEW 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. Rodinia transgression Pangaea Paleozoic Cambrian; trace fossils Ordovician Silurian Devonian Carboniferous Mississippian; Pennsylvanian Permian Gondwana Laurentia Siberia; Baltica; Kazakhstania Iapetus Ocean collision Laurasia Hercynian orogeny Altai Mountains Uralian orogeny Panthalassa equator ice-free limestone South Pole; sea level tillite; striations carbon dioxide coal formation arid climate weathering continental platform Appalachian Mountains docking clastic wedges Taconic orogeny Queenston clastic wedge Caledonian orogeny Baltica Old Red Sandstone Acadian orogeny Catskill clastic wedge conglomerates Allegeheny orogeny Piedmont Blue Ridge Valley and Ridge Ouachita orogeny passive margin Antler orogeny thrust Ancestral Rockies cratonic sequences quartz-rich sands unconformity 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. Sauk sequence Tippecanoe sequence Kaskaskia sequence Absaroka sequence craton cyclothems transgression;regression coals 400,000 ice sheets PRACTICE TESTS Multiple-Choice Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. a b d b c b d a c d a b c a b d c a b d b c b a d c b True or False Items 1. False. The earliest Paleozoic landscape was entirely barren of plants and animals. 2. True. 3. False. The last Paleozoic system is the Permian System. 4. False. East and west Gondwana did not collide to form Gondwana until the Middle Cambrian. 5. True. 6. False. Siberia and Kazakhstania were the last continents to be joined to form Pangaea. 7. False. Paleozoic ice ages were most common in the southern continent of Gondwana during the Paleozoic Era. Copyright © Houghton Mifflin Company. All rights reserved. 189 8. False. The late Permian warmth came from several factors, including the positioning of Pangaea on the equator, its great width, the loss of environments for limestone production, and the loss of chemical weathering due to reduced precipitation. 9. True. 10. True. 11. False. The erosion of the Taconic Mountains filled the Appalachian foreland-basin with the Queenston clastic wedge. 12. True. 13. False. Tectonic activity did not begin in western North America until the Late Devonian Period. 14. True. 15. True. 16. False. Since the Cambrian craton was located far to the east of the present-day Grand Canyon, the Tapeats Sandstone of the western Grand Canyon region was deposited earlier, and as the Cambrian seas transgressed eastward, the Tapeats Sandstone of the eastern Grand Canyon region was deposited later, nearer to the craton. 17. True 18. False The Williston Basin was an active site of evaporite deposition during the Kaskaskia sequence. 19. False Final regression of the seas in Late Permian time brought on widespread deposition of continental redbeds throughout the southwestern United States. 20. True Essay Questions 1. The assembly of Pangaea involved four major continental collision events: a. The assembly of Gondwana in Middle Cambrian time resulted from the collision of East and West Gondwana. b. The assembly of Laurasia in Late Silurian time resulted from the collision of Laurentia and Baltica. c. The initial assembly of Pangaea resulted from the collision of Gondwana and Laurasia during the Late Paleozoic. d. The final assembly of Pangaea occurred as Siberia collided with Kazakhstania during the Pennsylvanian Period, and Baltica collided with Kazakhstania during the Permian Period. The resulting supercontinent stretched from pole to pole, and contained virtually all land masses. 2. The Appalachian Mountains were built by four major orogenies in the last one billion years, but the Allegeheny orogeny has left the most dramatic structural changes. In the Piedmont province, which was located closest to the site of continental collision with Africa, intense metamorphism and numerous intrusions greatly affected the already deformed rocks. In the Blue Ridge province, great Copyright © Houghton Mifflin Company. All rights reserved. sheets of Proterozoic rocks were thrust eastward towards the craton. In the Valley and Ridge province, the great wedges of sediments shed into the foreland-arc basins were folded and faulted In the plateau province, the thinning distal basin sediments were tectonically undeformed, and represent shallow marine environments that contain abundant fossils. 3. Rising sea levels across the craton of North America from the east, south, and west left similar sedimentary sequences (that could be correlated) as they lapped upon the continental interior. Eventually, most of North America except for a portion of the Canadian Shield, and the islands of the Transcontinental Arch was underwater.The intial sedimentary deposit of such a sequence began with quartz-rich sands eroded from the continental interior. As sea level rose, these sediments were repalced with deeper-water muds, and then offshore, platform limestones. When sea levels fell, much of the sedimentary thickness previously deposited was removed by erosion, resulting in a widespread erosional surface or unconformity. 4. Cyclothems are represented by the orderly, repetitive alternation of sediments produced in a succession of adjacent depositional environments. In the eastern part of North America, thin sequences of sediments of Pennsylvanian age shift back and forth between basal nonmarine (stream and deltaic sandstone, siltstones, and coal) to higher marine (shallow marine shales and limestones) strata. Rise and fall of sea level produced these changes, but the frequency and rapidity with which these changes occurred precludes any tectonic causes for cyclothem formation. The existence of ice sheets in Gondwana during this entire time interval provides the best explanation. Nonmarine strata would result from buildup of the glaciers and worldwide lowering of sea level, and marine sediments would follow the rise of sea level following the melting of glaciers. When the ice sheets finally retreated in the Permian Period, cyclothems disappeared. CHALLENGE TEST Completion 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. Canada; Greenland; Siberia breakup; assembly; fossils Mississippi River Valley; Pennsylvania Africa; South America Baltica; Laurentia Africa southern Baltica Baltica; Kazakhstania epeiric global cooling 190 12. 13. 14. 15. 16. 17. carbon dioxide Appalachian Mountains foreland-basin Laurasia Ouachita eastern Multiple-Choice Questions 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. c d d c d b c a a d d c b d c True or False Items 1. True. 2. False. The Carboniferous System is not recognized in the United States. 3. False. The closing of the Iapetus Ocean began the tectonic processes responsible for the building of the Appalachian Mountains. 4. True. 5. False. The single, large ocean surrounding the supercontinent of Pangaea was called Panthalassa. 6. True. 7. False Widespread glacial episodes may result from drastically lowered levels of carbon dioxide in the atmosphere, but they do not cause them. Reduction in limestone production and coal formation during glacial episodes cause carbon dioxide levels to rise, eventually causing the ice sheets to melt. 8. True 9. True 10. False. The Taconic orogeny involved the collision of Laurentia and Avalonia. 11. True. 12. False. Redbeds of the Catskill clastic wedge represent alluvial plains and stream floodplains, as indicated by the abundant fossil plants they contain. 13. False. The Piedmont structural province was characterized by intense metamorphism and numerous intrusions. 14. False. The Ancestral Rockies rose along high-angle faults that formed because of stress from the Ouachita orogeny. Copyright © Houghton Mifflin Company. All rights reserved.