1 / 27

The Late Paleozoic Era

The Late Paleozoic Era. Geology 103. Sea level changes. Kaskasia transgression starts in Devonian, continues to the end of the Mississippian Absaroka transgression begins in Pennsylvanian, continues to Triassic. Late Paleozoic plate configuration. Basically, Pangea is assembling

chaney
Download Presentation

The Late Paleozoic Era

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Late Paleozoic Era Geology 103

  2. Sea level changes • Kaskasia transgression starts in Devonian, continues to the end of the Mississippian • Absaroka transgression begins in Pennsylvanian, continues to Triassic

  3. Late Paleozoic plate configuration • Basically, Pangea is assembling • Gondwana still exists (over South Pole for most of this) and Laurentia is equatorial

  4. End Paleozoic plate configuration • At end of Paleozoic, Pangea is complete • Tethys ocean begins opening in the east

  5. Acadian orogeny continues through Devonian • To the north, Laurentia + Baltica = Laurasia • To the south, an island continent called Avalonia accretes onto southern Laurentia

  6. Catskill clastic wedge and some crystalline rocks are all that remain • When the 4000+ meter mountains are eroded away, all that remains are: • their crystalline roots, both metamorphic and intrusive igneous • Their erosion products in the clastic wedge

  7. Roots of mountain ranges

  8. Alleghenian/Ouchitan orogeny – Miss. - Permian • Alleghenian orogeny is a result of a collision between parts of northern Laurasia and Gondwana, which spread southward to present-day Oklahoma, Texas, Louisiana, Venezuela (Ouchitan orogeny)

  9. Ancestral Rockies orogeny • Around the same time (Miss. – Permian), compressive forces in the middle of Laurasia created a series of ranges and basins (the ancestral Rockies) • Many basins become oil-producing regions (Big Horn Basin), not just in North America (Perm Basin, Russia)

  10. Western North America has been quiet since the Antler orogeny, but in Permian, Sonoma orogeny begins

  11. Late Paleozoic life diversifies but is marked by two extinctions • End of Mississippian • End of Permian (greatest of all extinctions) – 90% of marine species and 70% of land species go extinct

  12. Mississippian in Laurentia was characterized by extensive limestones Crinoids (modern sea lilies), blastoids, bryozoans and fusilinid forams

  13. Reconstruction of Mississippian sea floor

  14. Tetrapod evolution • Some fish had developed lungs • Changes to fin structure led to feet – land animal • Transitional form – Tiktaalik (375 my)

  15. Amniote egg evolution • Amnion = “membrane around fetus” • Group within tetrapods that produce eggs that are surrounded by membrane(s) • First of this type around 340 my • Synapsids (which lead to mammals) and sauropsids are part of these

  16. Tetrapod cladogram

  17. Pennsylvanian in Laurentia was a time of extensive coal deposition • To make so much coal, lots of carbon dioxide was “scrubbed” from the air • Atmospheric CO2 drops to a tenth of previous (about modern day values)

  18. Massive CO2 drop may have removed some greenhouse warming, resulting in mid-Carboniferous ice age

  19. Deposition of cyclothems • Cyclic sedimentary “package” of rocks, ranging from coal to limestone • Each cycle represents about 400,000 yr • The standard interpretation is that there are small transgressions and regressions at coastal regions where there are swamps

  20. Permian in Laurentia was a time of extensive deserts • Pangean continental interiors were dry, so extensive deserts and dunefields formed • Result are arenites with huge (meter-scale) cross-beds

  21. Therapsids, ancestors of mammals • Division of synapsids • Still are reptiles but have some mammalian characteristics like hair, lactation and erect posture • “apsid” = arch, typically over a hole in the skull (“fenstra”)

  22. Almost for naught – Permian extinction which occurs in less than 1 million years

  23. Causes of P/T extinction – climate change • Supercontinent interior generates extremes in temperature – 50°C average temperature in the interior • Habitable areas reduced

  24. Causes of P/T extinction – climate change • At Hallett Cove, South Australia, among other sites, extensive glacial striations exist in exposed bedrock of end Permian times • Worldwide glaciation was already occuring regularly during Permian • Regressions caused by glaciations remove habit on continental shelf

  25. Causes of P/T extinction – massive vulcanism • Siberian traps are a region of huge outpourings of basaltic lava around the end of the Permian • Increase CO2 in atmosphere, as well as dust

  26. How does a massive volcanic eruption cause enough climate change for a mass extinction? Initial temperature rise due to eruption CO2 increase warms oceans enough to exsolve trapped methane from ocean floor, which increases the warming

  27. Causes of P/T extinction - impacts • Potential impact sites of the right timing in Australia and Antarctica • Identified through presence of shocked quartz and stishovite, a high pressure form of quartz

More Related