PreCambrian
Archean:
Continents form
Granite, Gneiss, Greenstone Belts
~30% of continental mass
2 super continents
Rodinia (Grenville orogeny)
Pannotia (break up represents start of Paleozoic)
Early atmosphere
~1% oxygen
Photochemical disassociation
photosynthesis
Proto oceans develop
Paleozoic Continental Development
Beginning of PZ there are 6 major continents.
Baltica
China
Kazakhstania
Siberia
Gondwana
Africa, Antarctic, Australia, Florida, India, Madagascar, S. Europe, and Mid-East
Laurentia
Most of N. Amer, Greenland, Ireland, & Scotland
Cambrian
Major continents at Tropical latitudes
Polar regions on earth mostly ice free
End of Cambrian epeiric seas covered large portions of the land
What is an epeiric sea?
These are shallow inland seas
They have occurred many times in earth’s history
Recognized by sequences of rocks known as transgression and regression sequences
Created as sea levels change on earth
Glacial or interglacial periods
Rapid or slow rate of plate tectonics
Cratonic sequence
Consists of a transgressive and a regressive cycle topped by an unconformity
4 major cratonic sequences in N. America during the Paleozoic
Cambrian
Major continents at Tropical latitudes
Polar regions on earth mostly ice free
End of Cambrian epeiric seas covered large portions of the land
Plate motion in Paleozoic
In general, plates begin to move together
By the end of the Paleozoic Pangaea is formed
South pole is glaciated
Glacial till deposits
Carboniferous (Miss and Penn)
Gondwana moves over S. Pole and becomes extremely glaciated
Glaciation moves up to temperate latitudes
Gondwana and Laurasia begin colliding and this continues through the carboniferous
Pangaea assembled by Permian
Mountain Building during the Paleozoic
Building of the Appalachians
3 stages
1) Taconic Orogeny:
Beginning of the Appalachians
Subduction and folding of passive margin sediments
2) Caladonian Orogeny
Building of Caladonian Mountains in Europe
Continental to continental collision
3) Acadian Orogeny
Finish of orogeny…assembly of Pangaea
West coast Mountain Building
Subduction zone forms off West coast
Volcanic Islands form and eventually accrete to N. America
Antler Orogeny
First mountain building event for west coast
Accretion of volcanic Island arc
Forms ancestrial Rocky Mountains and adds material to continent
Coal Zones of the Carboniferous
(Mississippian & Pennsylvanian)
E. North America, W. Europe and Ukraine all located in equatorial regions
End of Paleozoic
Large continental ice sheets still on southern part of Pangaea
But begin to retreat
One large ocean (Panthalassa)
Climate at this time was fairly arid
Rain shadow effect
Most land away from ocean influence
Rain mostly at 40-60oN
Summery of Plates in PZ
Start with 6 major continents…end with one
Glaciation off and on at southern pole. Leaves glacial deposits for evidence
Epeiric Seas cover many continents throughout time period
N. America had 4 cratonic sequences
Several orogenies from subduction and collision of continents
Appalachian/Caledonian mountains
Ancestral Rocky mountains
PZ Life (Chapter 21—not assigned)
Cambrian Explosion
Animals with Skeletons appear in fossil record
Fairly suddenly (geologically speaking)
Extreme diversification of organisms
Confined to ocean environment
Primarily Trilobites, brachiopods and reef builders
Burgess Shale
Cambrian in age
Best example of soft bodied fauna and flora of this time
Found in Sauk sequence transgressive rocks
Very controversial hypothesis regarding this grouping of organisms
First hypothesis
Experimentation with body forms
Organisms went through mass extinction.
More diversity of structure then than we have now
Second hypothesis
No mass extinction
Many of these forms are basis for organisms today
Diversity of body forms has expanded since this time
PZ Oceans
Ordovician to…
Rugosa corals, bryozoans, tabulate corals, Cephlopods, Crinoids,
…Permian:
Fish, Reptiles, Amphibians, Land plants
Mass extinctions occur many times in Paleozoic
End Ordovician more than 100 families go extinct
Possibly due to Gondwana glaciation
End Devonian reefs collapse & lose many fish
End Permian Greatest recorded mass extinction in earth’s history (90% marine invertebrate, 65% amphibians and reptiles and 33% of insects)
Why Permian Extinction?
Several possible reasons
Meteorite impact
Ocean regression due to glacial conditions
Formation of Pangaea reduced continental shelf
Climate change due to Pangaea
Changes in ocean salinity and oxygen levels
Review Paleozoic
What is an epeiric sea and how many were there during the paleozoic
What is a crationic sequence (be specific)
How many orogenies were involved in building the Appalachian mountains and what were they?
Where was the Antler Orogeny located?
How many continents were there at the end of the Paleozoic?
What was the Cambrian explosion and why is the Burgess Shale important
What are some hypothesis about what caused the major extinction at the end of the Paleozoic