Lecture 10: Carboniferous Coal Swamps Flashcards
What is the principle of superposition?
oldest layers are at the bottom of a sequence an youngest are at the top
How do sedimentary rocks form layers?
they form from deltas that bring in new sediments in layers
What was the physical setting of the late Ordovician to Devonian period?
large land masses in the tropics –> high humidity and little seasonal variation
Many warm, shallow seas in coastal areas, estuaries, deltas and freshwater habitats
Erosion of young mountains like the appalachians means rivers carries lots of sediments into large deltas
This means nutrients and organic debris accumulated near coastlines
how did plant evolution affect river systems?
Plants evolved more roots which provided structure to the ground and stabilized banks, allowing single channels to develop within rivers
What is the devonian “plant hypothesis”
the spread of vascular plants affected surface weathering patterns –> increased weathering and nutrient runoff which promoted plankton blooms and increased photosynthesis, which increased atmospheric O2 and decreased atmospheric CO2 which cooled down the planet leasing to glaciation and mass extinction of tropical oceans.
What are the two types of carboniferous coal swamp formations?
1) delta system: organic material was buries by changes in sea levels
2) meandering river system: organic material was buries by cycles of flooding related to sea-level changes
How do cycles of rising and falling sea-levels affect coal and cyclothems?
organic matter accumulates in coastal swamps –> rising sea levels cause marine sediment to bury the swamp matter –> this process repeats resulting in various layers or marine sediments and organic deposits (cyclothems)
How do rising and falling of sea levels affect meandering river systems flooding?
sea levels rising causes rivers to flood and river sediments cover vegetation on floodplain and deposit them.
