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Homework question on geology?

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While hiking in the mountains of West Virginia, you find a sedimentary rock made up of angular grains of many different sizes. What do you know about this rock related to the distance from the source of the sediment, and the extent of transport. How do you know this?

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  1. It appears that you have a few clues to help you.  Now, I'm not a geologist, but by my 'name' you should realize that I enjoy my rocks.

    Angular grains mean that they haven't been exposed very long to the environment.  The longer the exposure to the elements, the rounder the grains would be.  

    Many different sizes mean that the grains have not been sorted.  This would mean that the grains have not been carried very far, since 'heavier' grains and 'lighter' grains would settle at different places, given more time/distance.

    So basically, you have a fairly young rock (probably) and its source was from rocks that were close.  The grains never had a chance to get sorted and they never were weathered.  


  2. Maficboy has rightly suggested that the unsorted fragments indicate short transport. That means the source (Provenance) is nearby. Angular grains also indicate same thing because a transported grain would lose its angularity and become rounded gradually. Please also check whether the fragments (called Framework) are of same material or different material.

    One other possibility is a Fault Breccia, if you can detect a fault nearby.

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