Dynamic Surface L5 Flashcards
What are the 6 major controls on carbonate sedimentation?
Geotectonics
Climate
Sea level
Salinity
Water depth
Turbidity
How does geotectonics affect carbonate sedimentation?
Geotectonics will dictate what kind and how much sediment will be deposited in the margins of an ocean basin via river systems.
At what latitudes do we see the most rapid accumulation of carbonates?
30N to 30S (Tropics)
How does the growth of mid-ocean ridges affect carbonate sedimentation?
The addition of a mid-ocean ridge in the sea increases the sea level as water is displaced upwards resulting in the flooding of continental margins.
How does temperature and salinity affect carbonate sedimentation?
Raising the temperature results in higher salinity due to evaporation of sea water. Inorganically precipitated carbonate needs temperatures somewhere in excess of 18C.
At what annual temperature range of water is carbonate production highest?
15-25C
What is an indicator of hyper-saline conditions?
Peloids
In what zone of the sea is carbonate production highest?
The Photic Zone
At what depth is reefal growth highest?
<5m
What is turbidity?
The level of cloudiness of water due to suspended sediment (low turbidity = clear, high turbidity = murky)
How does turbidity affect carbonate sedimentation?
Hight turbidity cuts out the light that reef organisms (biomineralisers) depend on causing them to die
What are the 5 carbonate platforms?
Rimmed shelves
Ramps
Epeiric platforms
Isolated platforms
Drowned platforms
What is a carbonate platform?
The shallow areas around continental margins that are particularly abundant at times of high sea level
What is a rimmed shelf?
A platform that extends out 10-100km from the continental margin up to a point where there is a slight topographic high and then a rapid descent into deep water
How can the topographic high of a rimmed shelf be formed?
Reef structures
A bank of carbonate sediment that has been assembled by wave action
What is a ramp carbonate platform?
A continental margin where you see a gentle slope down into the ocean basin that have a width of 10-100km.
How is a ramp carbonate platform formed?
As we move into deeper water along the ramp, there is an accumulation of carbonate particles driven up to this point by wave action which often form beaches and strands. This protects the shallower region behind it creating a low energy environment where we find hyper-saline conditions, lagoons and tidal flats.
What is an epeiric platform?
Huge carbonate platforms with widths between 100 and 10,000km that were extremely shallow (chest deep) and tidal swept.
What is an isolated platform?
Areas of topographic highs in major ocean basins with a width of 1-100km. Found on top of sea mounts or banks which have been separated by continents by tectonic activity.
What is an atoll?
A type of isolated platform in which sinking sea mounts on which reef building organisms grow upwards as the sea mount sinks.
What is a drowned platform?
A carbonate platform that has prograded forwards and then turns into a rimmed shelf which is buried by later clastic sediments
