Historical Geology 102
Paleozoic Era II


Late Paleozoic

Devonian Period: 416 - 359 m.y.
Mississippian Period: 359 - 318 m.y.
Pennsylvanian Period: 318 - 299 m.y.
Permian Period: 299 - 251 m.y.

Devonian Period

Acadian Orogeny
N. America and Baltica began convergence in the Silurian
Major mountain building episode
NE portion of continent - Newfoundland, Greenland into Scotland and Norway
Laurentia + Baltica = Laurussia
SE margin - ocean-continent collision

Antler Orogeny

Same time as the Acadian Orogeny
Western margin of N. America - subduction zone develops
Volcanic arc develops initially
Inland thrust faulting results in the formation of the Antler Mountains
Begins in the Devonian - continues into the Pennsylvanian

Kaskaskia Sequence

Kaskaskia Sea transgression in early Devonian
Deposit of sandstone - two sources
1) Older sediments eroded from the shield area and older sediments
2) Acadian Highlands - unaltered garnet grains
Erosion, carbonate deposits, clastic wedges

Mississippian Period

Kaskaskia Sea regression begins
Period of widespread erosion begins between Kaskaskia and Absaroka Sequences
Large areas of carbonate deposition
Antler Orogeny continues in west
NW margin - Franklin Highlands form due to ocean-continent collision.

Pennsylvanian

Absaroka Sequence - differs from earlier sequence deposits
Alternating marine and non-marine deposition
Deposition during a single transgression and regression is called a cyclothem
Typical cyclothem in Illinois has 10 units.

Cyclothems

Lower units are non-marine deposits - Coal Beds - Underclay - Fresh water limestone - Sandstone
Upper units are marine deposits: - Limestone - Shale
Extensive deposits covering large areas from Kansas to New York
World-wide occurrence of cyclothems
At least 50 cyclothems are known during this time period.
What causes sea level to change?

Eustasy

Eustasy - sea level changes
Changes in sea level result in transgression or regressions.
Causes of eustasy:
1) Tectonic Activity
2) Isostasy
3) Glaciation

Cyclothems

Global event
Gondwanaland was located in the South Polar region during this Period.

Ouchita Orogeny

Closure of the ocean between Laurussia and Gondwanaland
Collision of the two continents results in deformation along the southern margin of N. America
Ouchita Mountains in Arkansas and Texas - fold belt

Ancestral Rockies

Same time as Ouchita Orogeny, major uplifting is occurring in the western interior.
Most major tectonic activity occurs along the plate margins.
These uplifts are occurring away from an active tectonic boundary.
How is this possible?
Ancestral Rockies were located in the same location as the present Rocky Mountains.
How do we know the Ancestral Rockies existed when the Rocky Mountains are there now?

Permian Period

Absaroka Sea regression begins
Marine deposition is limited to narrow bands along continental margins (worldwide).
Allegheny Orogeny (also known as the Appalachian Orogeny)
Began during the Pennsylvanian
Collision of Laurussia and Gondwanaland

Sonoma Orogeny

Collision of island arcs with Laurussia along the southwest margin of the continent.

Global Events - Devonian Period

Devonian Paleogeography
Laurussia forms - N. America and Baltica
Closure between Baltica and Siberia continues
China is moving towards Siberia

Global Events - Carboniferous Period

Mississippian Paleogeography
Pennsylvanian Paleogeography
Large, extensive continental glaciers develop on Gondwanaland causing fluctuations in sea level - cyclothems
Laurussia begins colliding with Gondwanaland

Global Events - Permian Period

Permian Paleogeography
Siberia collides with Baltica - forms the Ural Mountains
China collides with Siberia
Formation of Pangaea - Laurasia collides with Gondwanaland
By the end of the Permian all of the major continental land masses had collided together to form a supercontinent.

Additional Resources

Paleogeography Maps

The following are a series of incredible maps researched, drawn and copywrited by Dr. Ron Blakey at Northern Arizona University.

Permian Paleogeography
- Global - 260 m.y.
- North America - 260 m.y.
- North America - 275 m.y.
- Global - 280 m.y.
- North America - 290 m.y.
Pennsylvanian Paleogeography
- Global - 300 m.y.
- North America - 300 m.y.
- North America - 315 m.y.
Mississippian Paleogeography
- North America - 325 m.y.
- Global - 340 m.y.
- North America - 345 m.y.
Devonian Paleogeography
- North America - 360 m.y.
- Global - 370 m.y.
- North America - 385 m.y.
- Global - 400 m.y.
- North America - 400 m.y.
Silurian Paleogeography
- North America - 420 m.y.
- Global - 430 m.y.
- North America - 430 m.y.
Ordovician Paleogeography
- Global - 450 m.y.
- North America - 450 m.y.
- Global - 470 m.y.
- North America - 470 m.y.
- North America - 485 m.y.
Cambrian Paleogeography
- Global - 500 m.y.
- North America - 500 m.y.
- North America - 510 m.y.
- Global - 540 m.y.

Additional paleogeographic maps and animations can be found at the PALEOMAP Project by Christopher R. Scotese.