Late Paleozoic (midterm 2) Flashcards
(40 cards)
What are the 3 periods in the Late Paleozoic Era
Devonian
Carboniferous
> Mississippian and Pennsylvanian
Permian
What are mobile belts?
(aka orogenic belts) - they are elongated zones of Earth’s crust that have had structural deformation, often associated with mountain building and plate tectonics
Explain the Appalachian mobile belt evolution from the Neoproterozoic/early Ordovician to the middle Ordovician
Neoproterozoic/early Ordovocian: spreading centre, divergent plate boundary, widening of lapetus ocean
- one side is Laurentia (passive margin)
- the other side is Baltica (Europe) (also passive)
Then we have oceanic-continental convergent plate boundaries on both sides (both margins/sides are now active)
- Taconic highlands on Laurentia margin and Caledonian highlands on Baltica margin
*check diagram in photos
What is a clastic wedge?
A large accumulation of mostly detrital sediments deposited in a basin next to uplifted areas
Describe the tickness of the sediments of the Queenston Delta Clastic Wedge
In the Queenston Delta wedge, sediments are thickest and coarsest near the Taconic Highlands and thin away from them
What are the sea level trends during the late paleozoic?
Sea levels are going up and down but by the end of the Paleozoic they’re pretty constant and close to modern levels
In what geologic period does Pangaea form?
Permian (late Paleozoic)
Give a summary of the Late Paleozoic Paleogeography (environment and climate)
Major glacial cycles occurred over much of Gondwana during the Late Mississippian (Carboniferous) and early Permian
A variable global climate during the Late Paleozoic is suggested by large coal, evaporite, and tillite deposits around the world
Pangaea formed by the end of the Permian, dramatically altering ocean and atmosphere circulation patterns
Explain the Paleogeography during the late Devonian Period (mountains, sea, oceans, etc.)
Mountain building & global sea level rise
Southern lapetus ocean narrowed between Laurasia & Gondwana
mountains from Acadian Orogeny (eastern Laurasia) and Antler Orogeny (western Laurasia)
Erosion of highlands = red sediments
Explain the Paleogeography during the early carboniferous period (continent movement, mountains, seas)
Gondwana moved over South Pole
> Extensive continental glaciers
Sea levels rose and fell
Gondwana collides with Laurasia, setting off orogenies worldwide
Explain the Paleogeography during the late carboniferous period (mountains and deposits)
Mountain building where Gondwana & Laurentia collide
Ancestral Rocky mountains formed
Extensive coal swamps *source of most of the world’s coal supply today
Explain the Paleogeography during the late Permian (continents, ocean, mountains, etc.)
what are the common and restricted deposits?
Pangea fully assembled (Laurasia and Gondwana together)
Panthalassa ocean (encircling pangea)
Water temperatures stable from increased circulation
Size of supercontinent plus high mountains formed arid (dry) & semiarid climates in the interior *produced extensive red beds & evaporites; coal formation restricted
What were the 3 main environmental/climate periods during the late Paleozoic Evolution of North America?
- Extensive shallow marine carbonate deposition
- Large coal-forming swamps
- dry, evaporite-forming terrestrial conditions
The sea level changes during the late paleozoic evolution of north america were caused by what?
- glaciers on Gondwana
- tectonism from Pangaea assemblage
Explain the Kaskaskia Cratonic Sequence
Kaskaskia Sea transgressed (rose) over a low North American craton during the Middle Devonian and Late Mississippian
The sequence is partly made up of rocks from the eroding highlands of the Appalachian mobile blet
Explain reef development in Western Canada (middle and late devonian)
Reef deposits in western Canada formed as the Kaskaskia Sea transgressed > major reservoir rocks for petroleum
As the reefs grew and restricted the flow of sea water, extensive evaporite deposits formed - more than 50% of the world’s potash (used in fertilizers) comes from these evaporites
Explain how black shale deposits came about during the Devonian period - what is the value of black shale
Mid to late Devonian: deposition of shales replaced carbonate-evaporite deposition in parts of North America
End Devonian: widespread black shale formation over much of the North American craton
*black shales contain a lot of organic matter - can turn into oil and gas - very valuable
What isthe New Albany Shale and example of? What condition is needed to form?
- example of black shale outcrop >
- formed on the anoxic (low oxygen) bottoms of shallow seas
> Low oxygen conditions to prevent the decay of the organic matter - which is what allows it to turn into something valuable like a hydrocarbon
What is fracking?
Injection of fluids into the subsurface to fracture the rocks that have those hydrocarbons in the shale and we break it apart to be able to release it → drill a well and blast water into this layer, causing fractures in it to release the hydrocarbons
When was the Absaroka cratonic sequence and what were the mountain building episodes?
ABSAROKA During the PENNSYLVANIAN (late Carboniferous) and throughout the PERMIAN period
The Ouachitan and Alleghenian episodes
What process is tied into the evolution of the cratonic sequences
They are tied into transgressions and regressions of the sea level
Explain the environment / vegetation characteristics by the mid Pennsylvanian (308 Ma)
- terrestrial plants evolving
- extensive, lush, swampy forests in North America
- lots of vegetation material (which ended up giving us coal deposits)
- Cyclothems : repeating patterns of alternating marine and nonmarine strata
Much of Earth’s coal formed during the ______________
Late Carboniferous
> because at this time, large wetlands covered large areas of Earth
What is the significance of coal?
- provides much of the electricity for the US
- is important in steel production
