1. Deep-Sea Sediments

2. Two types of sediment cover most of the deep ocean floor:
Abyssal clay
covers most of the deep ocean floor
accumulates at a rate of about 1mm every 1000 years
mostly lithogenic sediment carried by ocean currents and wind.
Biogenous Oozes
must be composed of more than 30% biogenic material (skeletal fragments)
may be calcareous or siliceous
rate of deposition of oozes depends on biological activity and dissolution of the skeletal fragments.

3. Calcareous Ooze
Made mostly of the calcite (calcium carbonate, CaCO3) shells of foraminifera and coccolithophores
These planktonic organisms are dominant in warm surface waters in the world’s oceans
They make up 48% of deep ocean sediments

4. Carbonate Compensation Depth
At depths greater than 4500 m, the dissolved carbon dioxide (CO2) concentration is so high that it causes calcite to dissolve.
This is called the Carbonate Compensation Depth.
The CCD varies with temperature, salinity and atmospheric carbon dioxide.

5. Siliceous Ooze
Made mostly of silica (SiO2) shells of diatoms and radiolarians
These planktonic organisms are dominant in cold surface waters and in upwelling areas.
They make up 14% of deep ocean sediments.

6. Carbonate Compensation depth and Biogenous ooze accumulation

7. Abyssal Clays
Made mostly of clay minerals, and very fine grained, less than mm
Can be carried by winds to all parts of the world
They do not dissolve in water.
Dominant in the deep ocean in areas where oozes are absent
Especially dominant below CCD in warmer oceans
Make up about 40% of deep ocean sediment.

8. Distribution of Deep ocean sediment
Calcareous ooze is the dominant deep ocean sediment in warm water above the CCD, and along the mid- ocean ridges, seamounts and other peaks.
Siliceous ooze is dominant in cold water below the CCD, and where deep ocean currents upwell to the surface.
Abyssal clays are dominant below the CCD in warm water and wherever biogenous oozes are absent.

9. Distribution of Marine Sediment Types