Historical Geology Lecture Notes: Late Proterozoic - Carboniferous and Permian

Carboniferous Period (359-299 mya)

  • Named for massive coal deposits from extensive forests.
  • Divided into two epochs:
    • Mississippian: 359-323 mya.
    • Pennsylvanian: 323-299 mya.

Key Ecosystem Developments

  • Terrestrial Ecosystems:

    • Boom in diversity of new terrestrial ecosystems.
    • Initial forests comprised early seedless plants, leading to the formation of coal beds.
    • Gymnosperms appeared with naked seeds, including conifers and cycads.

  • Marine Ecosystems:

    • Recovery post-Devonian; diversification of ammonoids.
    • Amorphous armor gave way to enhancing mobility in aquatic life.
    • Radiated Foraminifera, specifically fusulinids, emerged in late Carboniferous.

Flora and Fauna

  • Brachiopods and Crinoids:

    • Brachiopods diversified following Devonian.
    • Crinoids created extensive "crinoid meadows" contributing to limestone formation.

  • Freshwater Ecosystems:

    • Diversification of sharks, rays, and clams.

  • Terrestrial Insects:

    • Emergence of winged insects with large body sizes due to increased oxygen levels.
    • Notable species: Dragonflies (2.5 ft wingspans), 8 ft long millipedes.

  • Amphibians and Reptiles:

    • Semi-aquatic amphibians reached 20 ft in length.
    • Late Carboniferous saw first appearance of reptiles with amniotic eggs, facilitating life on land.

Geological Changes

  • Convergence of continents in the Carboniferous, formation of Pangea.
    • Ouchitian and Alleghenian Orogenies: Major mountain-building events.
  • Climatic extremes shifted towards global cooling by mid-Carboniferous as glaciers formed on Gondwanaland.
  • Cyclothems observed: Alternating coal and ocean deposits indicate fluctuating environments.

Permian Period

  • Ecosystem Changes:

    • Dominance of reptiles with new jaw structures (e.g., Pelycosaurs).

  • Evolution of therapsids, ancestors to mammals, featured vertical leg placement for better movement.

  • End Permian Extinction:

    • Largest known extinction event due to Siberian volcanic eruptions (Siberian Traps).
    • Estimated 80% ocean species and 70% terrestrial life perished.

  • Geological Events:

    • Formation of massive deserts due to landmass from Pangea, leading to reduced plant life and increased greenhouse gas concentrations.