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Early Paleozoic Geology

Early Paleozoic Geology. Chapter 10 Part 1. Early Paleozoic Cambrian Ordovician Silurian. Precambrian rocks. Precambrian: formed First crust First continents First supercontinent (broke up too) Shield: exposed Precambrian rock Craton: buried and exposed Precambrian rock

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Early Paleozoic Geology

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  1. Early Paleozoic Geology Chapter 10 Part 1

  2. Early Paleozoic • Cambrian • Ordovician • Silurian

  3. Precambrian rocks • Precambrian: formed • First crust • First continents • First supercontinent (broke up too) • Shield: exposed Precambrian rock • Craton: buried and exposed Precambrian rock • Platform: the buried Precambrian rocks

  4. Mobile belts: • On edge of continents • Areas of mountain building (orogenies) • Associated with subduction zones • Volcanoes/intrusive rocks • If sediment deposited, deformed in collisions

  5. North American craton • Canadian shield • Platform • 3 major mobile belts • Cordilleran • Ouachita • Appalachian

  6. Late Cambrian Geography • Continents near equator, ice free • Laurentia and Gondwana

  7. Late Ordovician Geography • Gondwana heads to south pole • Laurentia near equator

  8. Silurian Geography • Gondwana at the south pole • Laurentia near equator

  9. Sequence: • package of sediments • Unconformities on top and bottom • Cycle of transgressions and regressions • Cratonic sequence: • Size of craton • bigger than supergroup

  10. N. American cratonic sequences ~460 Ma ~505 Ma Limestone Shale ~480 Ma ~530 Ma Sandstone ~510 Ma Limestone Precambrian Gneiss, schist >2 billion Shale ~545 Ma Sandstone Precambrian Gneiss, schist >2 billion

  11. North American Cambrian geography

  12. Sauk sequence • 1st transgression onto craton • Cambrian • Marine seds deposited on craton & mobile belts

  13. Sauk sequence, Cambrian • Grand Canyon stratigraphy

  14. Three formations in the Grand Canyon, Arizona • Unconformity • Tapeats sandstone over Vishnu schist

  15. Grand Canyon Bright Angel Shale

  16. Grand canyon Muav Limestone

  17. Sauk sequence on the east coast • Transgression • Sandstone, shale, limestone

  18. Cambrian Jordan sandstone in the Dells

  19. Parfrey’s Glen in Wisconsin • Cambrian Jordan Sandstone

  20. Cambrian limestone • Stromatolites in New York

  21. During Tippecanoe sequence Ordovician • North America at equator • Rotating counter clockwise

  22. Tippecanoe sequence • Transgression • Sands deposited on craton • Basal sandstone: St. Peter sandstone

  23. Tippecanoe sequence • Transgression • Sands deposited on craton • Basal sandstone: St. Peter sandstone

  24. Tippecanoe basal sandstone • St Peter sandstone: Matthesien State Park Buffalo Rock State Park

  25. Tippecanoe sequence, Silurian • Lots of limestones • Limestones mean reefs

  26. Tippecanoe sequence, Silurian • Michigan: lots of reefs and lots of evaporites

  27. Tippecanoe sequence • Over 400 feet of salt deposited in Michigan • How are we going to form this?

  28. Tippecanoe Sequence • How reefs can for evaporites

  29. North American Geography Silurian • Reefs form barrier • Currents cut off • Evaporation begins

  30. North American Geography Silurian • Form evaporites • Salt and gypsum

  31. Sauk sequence: • Late Proterozoic - Early Ordovician • Seas regress early Ordovician • Limestone now exposed, eroded • Formation of unconformity • Tippecanoe sequence • Middle Ordovician to early Devonian • Seas regress in early Devonian • Erosion of limestone again

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