Most with economic potential are from areas with moderate surface productivity and are rich in copper and nickel. They are richer than other ores, and may be the first for deep-sea mining. Fecal pellets sink rapidly and explain why sediments closely reflect the particle composition of overlying waters. Calcareous ooze - Its percentage coverage decreases with increasing depth. Also smaller oceans have a larger percent of the surface waters with a high productivity.
Siliceous oozes are less abundant because silica is always undersaturated in seawater.
These oozes are found below the CCD, and there is a belt of diatom ooze around Antarctica, which is too cold for calcareous shell-formers. Its distribution reflects the CCD in the Atlantic. Trenches in the Pacific restrict its deposition. There is increasing evidence for a major meteorite impact as the cause. Iridium enrichment of sediments at this boundary is good evidence.