A layer of sandstone is found on top of a layer of shale. What most likely happened in this area?

Mud was deposited first, then sand.

Explanation:

This could have been a tidal mud flat succeeded by a sandy beach, or along the bed and course of a river with either mountain building upstream causing faster flow and carrying of mud farther away or the sea level falling with mud deposits being found closer to the new coastline. Hope this helps!

14 days is the half-life of phosphorus-32

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