Paleozoic Geology

Floods, Glaciers, and The Birth of Pangea

Paleozoic

Era Age (Myrs) Epoch

0.01Holocene

1.8Pleistocene

5.3Pliocene

23.8Miocene

33.6Oligocene

54.8Eocene

65Paleocene

144

206

248

290

323

354

417

443

490

543

2500

3800

Precambrian

Phanerozoic

Eon

Proterozoic

Archean

Hadean

Period

Quaternary

Tertiary

Neogene

Paleocene

Mississippian

Cenozoic

Mesozoic

Paleozoic

Cretaceous

Jurassic

Age of the Earth 4600 Myrs (4.6 Byrs)Source: Geological Society of America (1999)

Geologic Time Scale

Devonian

Silurian

Ordivician

Cambrian

Triassic

Permian

Pennsylvanian

543-248 Myr

Early

Middle

Late

Key Events of the Paleozoic

1. Six major continents formed by the breakup of Rodinia converge to form Pangea

2. Sea Level rose to cover large sections of the continents four times

3. Two major Ice Ages chilled the planet4. Life diversified and moved to the land, but

was also “set back” by three major extinctions

1. The Growth of Pangea

Important Continents & Terrains, & Oceans of the Paleozoic

•Laurentia - North America•Baltica - Europe•Laurasia - formed by combination of Laurentia and Baltica•Siberia - Siberia•Gondwana - Africa, S. America, India, Ausralia, Antarctica•Pangea - late Paleozoic supercontinent•Taconic Arc - Volcanic Arc in the Iapetus Ocean•Avalonia - Microcontinent including England•Panthalasia Ocean - pre-Pacific Ocean•Iapetus Ocean - pre-Atlantic Ocean

Precambrian - Rodinia

Montana

New York

Gondwana & Laurentia

About 500 Myr

Map Symbols

Trench(Subduction Zone)

Spreading Center(Divergent Zone)

Orogony(Collision Zone)

Cambrian

Siberia

BalticaLaurentia

Gondwana

Ordovician

Silurian

Taconic Orogoney

Paleozoic “Clastic

Wedges” of sediment form

behind collision zone

Upper OrdovicianClastic Wedge

Isostasy

Why does a deep basin form?

Devonian

Mississippian

Pennsylvanian

Permain

AppalachianMountains

Important Paleozoic OrogeniesOrogeny Age What collided

Taconic Sil. Taconic Arc with Larentia

Caledonian Dev Larentia with Baltica (forming Laurasia)

Acadian Dev. Avalonian Terrane with Laurasia

Ural Penn. Siberia with Baltica

Hercynian Penn. European part of Laurasia with Gondwana

Alleganian Penn/

Perm

N. part of Laurasia with Gondwana (forming Pangea)

Ouachita Perm Southern part of Laurasia with Gondwana

2. The Rise and Fallof the Sea

“The Sea Come In, the Sea

Goes Out”

Transgression Regression

1

2

3

4

Sedimentary Sequences of NA

Blue = No deposition

Highs and Lows

Late Ordovician(Tippecanoe Sequence)

Early Devonian

Cyclothems

Evidence of changingSea Level

Causes ofSea Level Change

A. Local Sea Level Change1. Local Tectonic Movement

B. Global (Eustatic) Sea Level Change1. Ice Ages (water is trapped in ice)2. Rate of plate divergence at mid-ocean ridges

3. Changing Climate

Evidence for Climate Change

Rocks - Tillites, evaporites, coal, carbonates, etc.Fossils - Different species live in different climates

Warning - What else could rocks & fossils record?

Movement of plates

Evidence for Permian

Climate

Evaporites

Coal

PaleozoicIce Ages

1

2

3

4

5

Causes of Ice Ages

1. Changes in the balance between how much heatthe Earth and how much it loses

2. How heat is distributed on the Earth

What Causes Ice Ages

1. Changes in Position of the Continentso Polar continents = place to make glacierso Restricted ocean basins = colder

2. Changes in Sea Levelo Higher = more shallow water = hotter

3. Mountain ranges / timing of Orogenieso Mountian growth = colder

4. Change in Atmospheric Chemistryo Greenhouse gases = hotter

By the Permian it got hot &

stayed that way for a

while

Evaporites

Coal

Mass Extinctions:Death and Destruction

The Five Big ExtinctionsWhen(End of…)

Species Loss**

Major Loses to

Ordovician 85 ±3% Brachiopods & bryozoans

Devonian 83 ± 4% Rugose & tabulate corals, armored* & jawless fish

Permian 95 ± 2% All life! - Trilobites*, corals*, blastoids*

Triassic 80 ± 4% Most synapsids

Cretaceous 76 ± 5% Dinosaurs, marine reptiles, ammonites

*Went extinct, **From Jablonski (1991,1995)

Causes of Mass Extinctions

Major environmental change - to fast for species to adapt

Such as:Meteorite impacts

Massive global eruptionsRapid climate change

Major sea level fluctuations

Paleozoic Causes:Leading Hypotheses

Ordovician - related to ice ages?-lowering sea level-cooling climate

Devonian -related to the buildup of land plants-ultimately creating anoxic conditions in the ocean

Permian - Formation of Pangea-loss of shallow marine environment-climate change

-Massive volcanic eruptions-Comet impact

Survivors set the stage for the next “Age”

Adaptive Radiation

Key Events of the Paleozoic

1. Six major continents formed by the breakup of Rodinia converge to form Pangea

2. Sea Level rose to cover large sections of the continents four times

3. Two major Ice Ages chilled the planet4. Life diversified and moved to the land, but

was also “set back” by three major extinctions