Ocean Deposits

Ocean Deposits

1. Marine Sediments

2. Ocean sediment
Various materials settle through the water
column and accumulate on the ocean floor
Layers represent a record of Earth history,
including:
Movement of tectonic plates
Past changes in climate
Ancient ocean circulation patterns
Cataclysmic events

3. The 4 main types of sediment
1.Lithogenous = composed of fragments of
pre-existing rock material
2.Biogenous = composed of hard remains of
once-living organisms
3.Hydrogenous = formed when dissolved
materials come out of solution (precipitate)
4.Cosmogenous = derived from outer space

4. Origin of lithogenous sediment
Forms by:
Weathering =
breakup of exposed
rock
Transportation =
movement of
sediment
Deposition =
settling and
accumulation
Sediment-transporting media

5. Lithogenous sediment
composition
Most lithogenous
sediment is
composed of
quartz, which is:
Abundant
Chemically stable
Durable

6. Lithogenous sediment texture
Texture
includes:
Grain size
Sorting
Rounding
Maturity

7. Distribution of lithogenous
sediment
Lithogenous sediment occurs as:
Neritic (nearshore) deposits
Beaches
Continental shelves
Turbidites
Glacial-rafted debris
Pelagic (deep ocean floor) deposits
Abyssal clay

8. Origin of biogenous sediment
Organisms that produce hard parts die
Material rains down on the ocean floor and
accumulates as:
Macroscopic shells, bones, teeth
Microscopic tests (shells)
If comprised of at least 30% test material, called
biogenous ooze

9. Biogenous sediment
composition
Microscopic biogenous tests are
composed of 2 main chemical compounds:
1.Silica (SiO
2
) including opal (SiO
2
· nH
2
O)
Diatoms (algae)
Radiolarians (protozoan)
1.Calcium carbonate or calcite (CaCO
3
)
Coccolithophores (algae)
Foraminifers (protozoan)
Pteropod
Globigerina

10. Examples of silica-secreting
microscopic organisms
Diatom Radiolarian

11. Siliceous ooze
Silica-secreting
organisms
accumulate to form
siliceous ooze
(>30% siliceous
test material)

12. Examples of calcite-secreting
microscopic organisms
Coccolithophores Foraminifers

13. Calcareous ooze
Calcite-secreting
organisms
accumulate to form
calcareous ooze
(>30% calcareous
test material)

14. Biogenous ooze turns to rock
When biogenous
ooze hardens and
lithifies, can form:
Diatomaceous earth
(if composed of
diatom-rich ooze)
Chalk (if composed
of coccolith-rich
ooze)
Chalk cliffs of southern England

15. Distribution of biogenous ooze
Most biogenous ooze found as pelagic
deposits
Factors affecting the distribution of
biogenous ooze:
Productivity (amount of organisms in surface
waters)
Destruction (dissolving at depth)
Dilution (mixing with lithogenous clays)

16. Distribution of siliceous ooze
Silica slowly but
steadily dissolves
in seawater
Siliceous ooze
found where it
accumulates faster
than it dissolves

17. Distribution of calcareous ooze
Calcite dissolves
beneath the calcite
compensation depth
(CCD) at 4.5 km
Calcareous ooze can
be found below the
CCD if it is buried
and transported to
deep water

18. Biogenous ooze as
environmental indicator
Siliceous oozeCalcareous ooze
Surface water
temperature
Cool Warm
Main locations
found
Sea floor beneath
cool surface
water in high
latitudes;
upwelling areas
Sea floor beneath
warm surface
water in low
latitudes; not too
deep (CCD)

19. Origin of hydrogenous sediment
Hydrogenous sediment forms when
dissolved materials come out of solution
(precipitate)
Precipitation is caused by a change in
conditions including:
Changes in temperature
Changes in pressure
Addition of chemically active fluids

20. Types of hydrogenous sediment
Manganese nodules
Phosphates
Carbonates
Metal sulfides
Evaporite salts
Mining
manganese
nodules
Evaporite
salts

21. Cosmogenous sediment
Cosmogenous sediment is
composed of material derived
from outer space
Two main types:
1.Microscopic space dust
2.Macroscopic meteor debris
Forms an insignificant
proportion of ocean sediment
Microscopic
cosmogenous
spherule

22. Mixtures
Most ocean sediment is a mixture of
sediment types
One type of sediment usually dominates,
allowing it to be classified as primarily:
Lithogenous
Biogenous
Hydrogenous
Cosmogenous

23. Worldwide distribution of neritic
and pelagic sediment
Figure 4-17

24. Ocean sediments as a resource
Ocean sediments contain
many important resources,
including:
Petroleum
Gas hydrates
Sand and gravel
Evaporative salts
Phosphorite
Manganese nodules and
crusts
Offshore drilling rig