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Earth History GEOL 2110

Earth History GEOL 2110. The Paleozoic Era Late Ordovician Period Limestone, Limestone, and more Limestone and The Emergence of the Appalachians. Major Concepts.

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Earth History GEOL 2110

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  1. Earth History GEOL 2110 The Paleozoic Era Late Ordovician Period Limestone, Limestone, and more Limestone and The Emergence of the Appalachians

  2. Major Concepts • The great Sauk sea retreated to the edge of the NA craton about 480 Ma, when it transgressed the craton again (the Tippecanoe Transgression) over the next 50 million years, a whole new diversity of marine live came with it. • While Cambrian sands were initially spread over the craton as the Tippecanoe beach trangressed over the land, creating another ultrapure quartz sandstone formation – the St. Peter, this was quickly followed extensive deposition of fossil-rich limestone. • In the late Ordovician, the eastern margin of Laurentia transformed from a passive continental slope margin to a tectonically active volcanic arc – the Taconic. • Immature sediments shed westward from this arc accumulated between the continent and the volcanic arc and eventually became deformed and metamorphosed when the arc eventually collided and was thrust onto the continental edge –Penokean-like.

  3. The Tippecanoe TransgressionMid- to Late Ordovician

  4. The Ordovician “Explosion” • Changes in Ordovician from Cambrian Fauna • more complex food chain • extend higher above the seabed • hard part made of calcite rather than phospate

  5. Ecological Diversification of Ordovician FaunaIncreasingly Complex Food Web

  6. Multi-tiered Feeding Levels

  7. Arrival of Classic “Paleozoic” Fauna Articulated Brachiopods Crinoids “Sea Lillies” Bryzoans Sea Shells Twigs Cheerios

  8. …and the world’s best Index fossils! Conodonts Graptolites Ostracodes

  9. New Kids on the Block Jawless Bony Fish CarniverousNautiloid

  10. Why This Explosive Radiation? • An Early Ordovician regression followed by the most extensive transgression up to that point in Earth history • Enormous areas of shallow marine environments - niches • Atmospheric oxygen reaches modern-day levels

  11. The Tippecanoe Trangression St Peter SS – Platteville LS, St. Paul

  12. Capping the Craton in Limestone Except Here

  13. The Taconic Orogeny

  14. The Taconic Orogeny

  15. The Taconic Orogeny

  16. Modern-Day Analog

  17. Prior-Day Analog 1.85 GaPenokeanOrogeny

  18. Next Lecture The Paleozoic Era Cambrian and Ordovician History of Minnesota and Wisconsin

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