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Geology: the environments of some sediments

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  1. Apr 6, 2017 #1
    1. The problem statement, all variables and given/known data
    During a visit to mountainous area, students noticed a high mountain consists of 3 different parts: The top of the mountain consists of fossiliferous limestone. The middle of the mountain consists of fine grained rocks. The foot of the mountain consists of thick layers of boulder, gravel and tree trunks.

    Which of those parts belongs to a marine environment? And which belongs to an aerobic environment? And which belongs to a river environment?


    3. The attempt at a solution

    The top (fossiliferous limestone) -----> marine environment
    The middle (fine grained rocks) -----> aerobic environment.
    The base (boulder, gravel and tree trunks -----> River environment.
    Am I right?
     
  2. jcsd
  3. Apr 6, 2017 #2
    The first answer is right. I'm not sure, but I think the other two are switched. You usually think of fine grained rocks as an indication of river erosional sediment.
     
  4. Apr 7, 2017 #3
    But the base contains gravel and boulders which suggest high energy as in a river not an aerobic environment, right?
     
  5. Apr 7, 2017 #4
    Like I said, I'm not sure.
     
  6. Apr 7, 2017 #5
    Boulders can be found in river environments, but typically are not associated with river environments. With the mix of gravels, tree trunks, boulders you're looking at an aerobic environment near the source of those sediments. Typically you'll find the boulders and cobble and gravel sized piece near where they weathered and eroded off the source rock, also in glacial moraines. Rivers have to be extremely high energy to transport that type of large sediment. Your fine grained sands are going to be more river environments. And since they mentioned fine grained sands it's more likely a meandering or an anastomosing river which are lower energy.
     
  7. Apr 8, 2017 #6

    Borek

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    Staff: Mentor

    My bet is that the question wants you to eliminate two obvious things (marine & river), and then whatever is left must be a third pair.
     
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