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Early/late Paleozoic Geology

Early/late Paleozoic Geology. Chapter 10 and 11. Last time. Phanerozoic Eon Paleozoic Era Cambrian Ordovician Silurian. Last time. Sequences. Regression should have shale and sandstone as last rocks deposited. Where is the sandstone and shale on top in Sauk and Tippecanoe Sequences?.

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Early/late Paleozoic Geology

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  1. Early/late Paleozoic Geology Chapter 10 and 11

  2. Last time • Phanerozoic Eon • Paleozoic Era • Cambrian • Ordovician • Silurian

  3. Last time • Sequences

  4. Regression should have shale and sandstone as last rocks deposited. Where is the sandstone and shale on top in Sauk and Tippecanoe Sequences? Order of rock types Limestone Shale Sandstone

  5. North American craton • Appalachian mobile belt

  6. Rocks of the Appalachian mobile belt mid to end of Ordovician Volcanic ash in shales Shales, no mud cracks, no stromatolites mid-Ordovician- Silurian Cambrian- Early Ordovician Sandstone, stromatolites, Mud cracks, cross bedding

  7. Appalachian mobile belt in Cambrian • Passive margin and shallow water

  8. Appalachian mobile belt in Cambrian and Early Ordovician • Laurentia is still passive margin • Iapetus ocean opens w/ divergent margin

  9. Appalachian mobile belt in middle Ordovician-Silurian • Deeper water deposition (Tippecanoe Sequence)

  10. Middle Ordovician • Iapetus plate subducts under Laurentia • Volcanoes form • Onset of mountains • Taconic orogeny • Forms Taconic highlands • New York, Mass., Vt.

  11. How to date Taconic orogeny • Volcanic ash layers • Intrusive igneous rocks • 440-480 m.y.

  12. Evidence of Taconic orogen • What happens with formation of new mountains (highlands?) • Accumulation of detrital sediment • Thickest near mountains (source area) • Thinner, small particles away from source • Queenston Delta

  13. Evidence of Taconic orogen • What happens with formation of new mountains (highlands?) • Accumulation of detrital sediment • Thickest near mountains (source area) • Thinner, small particles away from source • Queenston Delta

  14. Early Paleozoic geology • Sauk and Tippecanoe sequences • Taconic orogeny

  15. Late Paleozoic • Devonian, Carboniferous, Permian

  16. Late Paleozoic sed rocks oldest • Tippecanoe sequence (ends early Devonian) • Unconformity/ erosion • Middle Devonian: transgression youngest

  17. Late Paleozoic sed rocks • Kaskaskia sequence • What rock is deposited first? • New York, Penn.

  18. Devonian Geography • Above sandstone: • Shales, limestones/ evaporites

  19. Kaskaskia sed. rocks • Devonian reefs of western Canada • Barrier reefs, evaporite basins • Sound familiar?

  20. New rock type in Kaskaskia: black shales • Black since organic-rich • Need: • High organic activity • Low oxygen water

  21. New rock type in Kaskaskia: black shales • Black since organic-rich • Need: • High organic activity • Low oxygen water

  22. End of Kaskaskia sequence • Return to limestones in Mississippian • Fossils of reefs!

  23. End of Kaskaskia sequence • Return to limestones in Mississippian • Fossils of reefs!

  24. Late Kaskaskia • Return to limestones in Mississippian • Fossils of reefs!

  25. Indiana Mississippian limestone Grand Canyon

  26. Famous Mississippian limestone • Indiana limestone • Empire mine

  27. Pennsylvanian • Late Mississippian: Kaskaskia Sea regression • Unconformity divides Mississippian & Pennsylvanian • Sea returns with Absaroka sequence

  28. New to Absaroka sequence • Sequence of marine/nonmarine rocks • What kind of sed. environment can we form these rocks? • Called cyclothems

  29. Complete cyclothem • Cyclothems contain coal • Coal is dead plants

  30. Cyclothems & coal • Okefenokee Swamp, Georgia

  31. Pennsylvanian coal swamps • How such widespread “delta” environments? • How could sea level change over such large area? • Glaciers in Gondwana

  32. End of Absaroka sequence • Permian • Lots of limestone! • West Texas

  33. Sandstone Limestone of Mississippian Black Shale Limestone & evaporites Sandstone Kaskaskia Sequence Sed. Sequences of N. America Limestone Coal Sandstone Absaroka Sequence

  34. Sed. Sequences of N. America Limestone with evaporites Limestone Shale Shale Sandstone Sandstone Tippecanoe Sequence Sauk Sequence

  35. Late Paleozoic sed rock summary • Kaskaskia: sandstone, limestone, black shale, limestone • Absaroka: sandstone, coal swamps, evaporites & limestones

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