Chapter 10-11 Paleozoic Earth History
Introduction In 1815, William Smith, a canal builder, published the world’s first geologic map. His hand-painted map represented over 20 years of work. England is a country rich in geologic history. Development of geology proceeded rapidly with the naturalists of the 19th century. The Paleozoic history is well represented there, involving several episodes of mountain building and sea level changes, mostly related to plate tectonics and glaciation. The Map that change the world S3
Continental Architecture: Cratons and Mobile Belts Most continents consist of two major components: 1. relatively stable craton over which epeiric seas transgressed and regressed 2. surrounded by mobile belts in which mountain building took place. Epeiric seas – shallow seas covering part of the craton Mobile belts – elongate areas of mountain building, primarily created during plate convergence
Paleozoic Paleogeography Six major continents existed at the beginning of the Paleozoic Era Four were located near the paleoequator. Baltica, China, Gondwana, Kazakstania, Laurentia and Siberia
Paleozoic Paleogeography • Early-Middle Paleozoic Global History • During the Early Paleozoic (Cambrian-Silurian): • Laurentia was moving northward and • Gondwana moved to a south polar location, as indicated by tillite deposits.
Paleozoic Paleogeography • Late Paleozoic Global History • During the Late Paleozoic (Devonian – Permian): • Baltica and Laurentia collided to form Laurasia. • Siberia and Kazakhstania collided and finally were sutured to Laurasia.
Paleozoic Paleogeography • Late Paleozoic Global History • During the Late Paleozoic (Devonian – Permian): • Gondwana moved over the South Pole • Gondwana experienced several glacial-interglacial periods, resulting in global sea-level changes and transgressions and regressions along the low-lying craton margins. Fig. 20.3 b, p. 528 S8 Fig. 20.3b, p. 528
Paleozoic Paleogeography • Late Paleozoic Global History • Laurasia and Gondwana underwent a series of collisions beginning in the Carboniferous. • During the Permian, the formation of Pangaea was completed. Surrounding the supercontinent was a global ocean, Panthalassa. S9 Fig. 20.4b, p. 530
Paleozoic Evolution of North America The geologic history of North America can be divided into cratonic sequences that reflect craton wide transgressions and regressions. There are 6 cratonic sequences recognized in North America. The study of cratonic sequences is called sequence stratigraphy In sequence stratigraphy rocks are studied within a time-stratigraphic framework related to facies and bounded by unconformities
The Sauk Sequence(Neoproterozoic – Early Ordovician) • The Sauk Sea was the first major sequence to transgress onto the craton.
The Sauk Sequence(Neoproterozoic – Early Ordovician) • During the transgressive portions of each cycle, the North American craton was partially to completely covered by shallow seas in which a variety of clastic and carbonate sediments were deposited. • This resulted in widespread sandstone, shale, reef, and coal deposits. S 12 Fig. 20.7, p. 537
The Sauk Sequence(Neoproterozoic – Early Ordovician) At its maximum, it covered the craton except for parts of the Canadian Shield and the Transcontinental Arch Transcontinental Arch - a series of large, northeast-southwest trending island.
The Tippecanoe Sequence(Middle Ordovician – Early Devonian) The Tippecanoe sequence began with deposition of an extensive sandstone over the eroded Sauk. During Tippecanoe time, extensive carbonate deposition took place. In addition, large barrier reefs enclosed basins, resulting in evaporite deposition within these basins.
Tippecanoe Reefs and Evaporites S15 Fig. 20.9, p. 539
Tippecanoe Reefs and Evaporites Fig. 20.11, p. 541 S16
Laminar stromatoporoid Anhydrite Halite Barrier reef Evaporite Carbonate Pinnacle reef Stromatoporoid barrier reef Limestone from the carbonate facies. Stromatolites Algal Niagara Formation Coral algal Crinoidal Clinton Formation Laminar stromatoporoid Core of rock salt from the evaporite facies. Cross section of a stromatoporoid colony from the stromatoporoid barrier reef facies. Stepped Art S17 Fig. 20-11, p. 541
The Tippecanoe Sequence(Middle Ordovician – Early Devonian) The End of the Tippecanoe Sequence By early Devonian, the Tippeecanoe Sea had regressed to the cratonic margin, exposing extensive low-lands. Mild warping of the craton produced many domes, arches and basins. Most of these were eroded down by the time our new sea, the Kaskaskia transgressed. S 18 Fig. 20.1, p. 525
The Kaskaskia Sequence(Middle Devonian – Late Mississippian) The basal beds of the Kaskaskia sequence deposited on the exposed Tippecanoe surface were either: • sandstones derived from the eroding Acadian Highlands or • carbonate rocks. S19 Fig. 20.13, p. 543
The Kaskaskia Sequence(Middle Devonian – Late Mississippian) Reef Development in Western Canada Most of the Kaskaskia sequence is dominated by carbonates and associated evaporites. The Devonian Period was a time of major reef building. A large barrier reef system restricted the flow of oceanic water, creating conditions for evaporite precipitation. S20 Fig. 20.14, p. 544
The Kaskaskia Sequence(Middle Devonian – Late Mississippian) • Black Shales • Widespread black shales were deposited over large areas of the craton during the Late Devonian and Early Mississippian. • Chattanooga Shale – • Thin-bedded • Highly-radioactive • Source rock for oil and gas • Origin highly debated. S21 Fig. 20.15, p. 544
The Kaskaskia Sequence(Middle Devonian – Late Mississippian) The Late Kaskaskia—A Return to Extensive Carbonate Deposition The Mississippian Period was dominated for the most part by carbonate deposition. The broad Kaskaskian epeiric sea covered most of North America. S22 Fig. 20.16, p. 545
The Absaroka Sequence(Pennsylvanian – Early Jurassic) What Are Cyclothems, and Why Are They Important? Pennsylvanian Period Transgressions and regressions, probably caused by advancing and retreating Gondwanan ice sheets, over the low-lying North American craton resulted in: cyclothems and the formation of coal swamps S23 Fig. 20.17, p. 546
Cyclothems S24 Fig. 20.18, p. 547
The Absaroka Sequence(Pennsylvanian – Early Jurassic) Cratonic Uplift—The Ancestral Rockies Cratonic mountain building, specifically the Ancestral Rockies, occurred during the Pennsylvanian Period Resulted in thick nonmarine detrital rocks and evaporites being deposited in the intervening basins. S25 Fig. 20.19, p. 548
The Absaroka Sequence(Pennsylvanian – Early Jurassic) • The Late Absaroka—More Evaporite Deposits and Reefs • By the Early Permian, the Absaroka Sea occupied a narrow zone of the south central craton. • Here, several large reefs and associated evaporites developed. • By the end of the Permian Period, the Absaroka Sea had retreated from the craton. S26 Fig. 20.22, p. 550 Fig. 20.23, p. 550
History of The Paleozoic Mobile Belts • Mountain-building activity took place primarily along the eastern and southern margins (known as mobile belts) of the North American craton during the Paleozoic Era. • Appalachian Mobile Belt • Several orogenies occurred in the Appalachian belt during the Paleozoic: • Taconic orogeny • Caledonian orogeny • Acadian orogeny • Hercynian-Alleghenian orogeny S27
History of The Paleozoic Mobile Belts • Appalachian Mobile Belt • Taconic orogeny • Throughout Sauk time, the Appalachian region was a broad, passive continental margin. A divergent boundary existed along the eastern side of Laurentia widening the Iapetus Ocean S28 Fig. 20.24, p. 551
History of The Paleozoic Mobile Belts • Appalachian Mobile Belt • Taconic orogeny • In mid-Ordovician time, the carbonate deposition ceased and was replaced with by deepwater black shales, graywackes and volcanics, marking the development of a subduction zone. S29 Fig. 20.24, p. 551
History of The Paleozoic Mobile Belts Appalachian Mobile Belt Taconic orogeny The final stage of the orogeny was marked by a thick sandstone deposit, the Queenstone clastic wedge, thinning away from the Taconic mountains. This wedge represents erosion of the Taconic Highlands mountain belt. S30 Fig. 20.25, p. 552
History of The Paleozoic Mobile Belts Appalachian Mobile Belt Caledonian orogeny The Caledonian mobile belt is the European equivalent of the Taconic mobile belt, forming the western border of Baltica facing the Iapetus Ocean A clastic wedge also formed along the front of these mountains called The Old Red Sandstone. S31 Fig. 20.24 b, p. 551
History of The Paleozoic Mobile Belts Appalachian Mobile Belt Acadian orogeny The Acadian orogeny occurred along an oceanic-continental convergent plate boundary.The plate carrying Baltica finally collided with Laurentia, forming a continental-continental convergent plate boundary. The closing of the Iapetus Ocean ended by forming a new continent called Laurasia. A new clastic wedge, the Catskill Delta, formed on the west side. S32 Fig. 20.26, p. 552
History of The Paleozoic Mobile Belts Appalachian Mobile Belt The Old Red Sandstone The Old Red Sandstone initially shed clastics from the Caledonian Highlands, then spread eastward onto the Baltica craton in Devonian. It is famous, as is the Catskill Delta, for its freshwater fish and early amphibian fossils, as well as early land plants. S33 Fig. 20.26, p. 552
History of The Paleozoic Mobile Belts Appalachian Mobile Belt The Hercynian-Alleghenian orogeny The Hercynian mobile belt in Europe and the Alleghenian mobile belt in North America mark the zone where Laurasia collided with Gondwana. The Hercynian-Alleghenian orogeny begins at its north end in Mississippian time and slowly moves to the south suturing together the continents as it goes. The first continent-continent collision is between western Laurasia and Gondwana. – Hercynian (Miss.) The next area to collide is eastern Laurasia and Gondwana. – Alleghenian (Penn.-Permian). This is the beginning of the formation of the supercontinent Pangaea. S34
History of The Paleozoic Mobile Belts Cordilleran Mobile Belt Antler orogeny In middle Paleozoic, a volcanic arc formed off the western margin of Laurentia. The subduction created thick deep water deposits that were thrust upon the craton when the volcanic arc collided with the craton in late Devonian. The Antler orogeny marks the collision. The Antler Highlands are composed of the deepwater deposits that were thrust onto the craton. S35 Fig. 20.27, p. 553
History of The Paleozoic Mobile Belts Ouachita Mobile Belt Ouachita orogeny Mountain building occurred in the Ouachita mobile belt beginning in late Mississippian, Pennsylvanian and Early Permian. Thrusting created a large mountain range extending from the Ouachita mountains in Arkansas to the Marathon mountains in far West Texas. S36 Fig. 20.28, p. 554
What Role Did Microplates and Terranes Play in The Formation of Pangaea? • During the Paleozoic Era, numerous terranes such as Avalonia existed and played an important role in forming Pangaea. • In addition to large-scale plate interactions, microplate activity played an important role in the formation of Pangaea. There were many microplates and terranes of various sizes present during the Paleozoic. • These were all involved in the formation of Pangaea. S37 Fig. 20.4 b, p. 530
Paleozoic Mineral Resources • Paleozoic-age rocks contain a variety of mineral resources, including: • building stone • limestone for cement • silica sand • evaporites • petroleum • coal • ores of iron, lead, zinc and other metallic deposits. S38 Fig. 20.29, p. 555
History of The Paleozoic Mobile Belts Appalachian Mobile Belt Acadian orogeny The Acadian mobile belt occurred along a convergent oceanic-continental boundary between Laurentia and Baltica. The Acadian orogeny marks the continental-continental collision. The closing of the Iapetus Ocean ended by forming a new continent called Laurasia. A new clastic wedge, the Catskill Delta, formed on the west side. S32 Fig. 20.26, p. 552
History of The Paleozoic Mobile Belts Appalachian Mobile Belt The Old Red Sandstone The Catskill clastic wedge has a European counterpart in the Old Red Sandstone The Old Red Sandstone initially shed clastics from the Caledonian Highlands, then spread eastward onto the Baltica craton in Devonian. It is famous, as is the Catskill Delta, for its freshwater fish and early amphibian fossils, as well as early land plants. S33 Fig. 20.26, p. 552