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Monday, May 6, 2013

Sedimentary Deposition Environment - where does the debris go?

Sedimentation
Where does all the debris go that has been eroded and how does it form a rock?

The general idea behind sedimentation is simple. Rocks are uplifted and then eroded by some medium, water or wind generally, and then once certain conditions are met the debris is deposited based on several variables. Generally speaking the smaller the particle and the high energy the medium the further that particle will get before it drops from a suspended load. This first image shows where certain particles generally settle out. Sand being the coarsest will drop out first, quarts and feldspar. Then the smaller clay particles will drop out, kaolinite, illite, chlorite, and vermiculite. Then when we get into the warm water one will encounter limestone, generally built by millions of dead sea organisms which have a calcium based shell. 
If you find this pattern of rock types you have encountered a sedimentary facies.
A facies is a pattern of rock type or rock unit that is different from adjacent rock units...depending on the depositional environment. A more detailed explanation of facies is to be explained later....

Sedimentary Deposition Environment


Now that we have an idea of facies...here is another pictorial example of where you may encounter different rock units depending on the depositional environment. We can see here that a swap will show shale and coal facies while the near shore environment will give us examples of sand and silt facies.


Sedimentary Facies

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