Devonian Period Notes

Devonian Period (419-359 Ma)

• Occurred within the Phanerozoic and Paleozoic eras.
• Subdivided into:
  • Upper (Late):
    • Famennian: $358.9 ± 0.4$ Ma
    • Frasnian: $372.2 ± 1.6$ Ma
  • Middle:
    • Givetian: $382.7 ± 1.6$ Ma
    • Eifelian: $387.7 ± 0.8$ Ma
  • Lower (Early):
    • Emsian: $393.3 ± 1.2$ Ma
    • Pragian: $407.6 ± 2.6$ Ma
    • Lochkovian: $410.8 ± 2.8$ Ma
• Dates approved by the International Commission on Stratigraphy (ICS) and ratified by the International Union of Geological Sciences (IUGS).

Silurian - Devonian Major Events

• Biotic Events:
  • Land plants and arthropods diversify.
  • First insects appear.
  • First land vertebrates (amphibians) emerge.
  • Marine recovery and renewed adaptive radiation after the Late Ordovician mass extinction.
  • Eurypterids are common.
  • Radiation of jawed fish.
  • First seeds and large trees; first forests.
  • Ammonoids become important predators.
  • Pentamerid and Spirifer brachiopods are common.
  • Mass extinction in tabulate-stromatoporoid reefs.
• Geologic Events:
  • Caledonian orogeny in Britain.
  • Extensive reefs and evaporites.
  • Local Gondwana glaciation (South America).
  • Antler orogeny.
  • Acadian orogeny and Catskill delta formation.
  • Tippecanoe sequence.
  • Kaskaskia sequence.

Devonian Paleogeography

• Euramerica (Laurentia + Baltica):
  • Located in subequatorial regions.
  • Low sea level in the Early Devonian.
  • Avalonia approaching.
• Orogenies:
  • Caledonian orogeny (Baltica + Laurentia) reaches its peak in the late Silurian/Early Devonian.
  • Acadian Orogeny: Collision of microcontinent Avalonia with North America in the Early-early Late Devonian.
    • Completes the formation of the continent of Euramerica.
    • Finishes the closure of the Iapetus Ocean.
• Acadian Orogeny Evidence: