Early/late Paleozoic Geology

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