Biogenic silica accumulates where there are plenty of nutrients. As an example, here is a cartoon of the east coast of North America. To the north, sediment is mostly terrigenous, with sand near the shore and mud farther out on the shelf. Below, the same image but with types of ocean sediment illustrated. For the shelf, sand is light green, mud is brown, dark green is gravel.
Limestone is pink.
Note also that north of Long Island, all the way to Nova Scotia, the dominant sediment is gravel. This sediment is till , and was deposited when glaciers advanced all the way from Canada to the Atlantic Ocean. In the deep sea, in the illustration above, chalk accumulates in shallow areas, such as the tops of seamounts, while r ed clay accumulates in the deepest areas. Two purple areas near Florida are areas where manganese nodules are accumulating. This is a diagram similar to Fig.