Siliceous ooze is one of the several types of soil that can be found on the floors of deep oceans. Not surprisingly, such layers occasionally contain an aquifer.
Siliceous ooze is a type of pelagic sediment. It is formed by the silica in diatoms and other microorganisms, as opposed to calcareous ooze, which is formed by particles of calcium carbonate.
A diatom, seen under a powerful microscope.