Marine sediments accumulate on the ocean floor from materials that settle through the water column and provide a record of changes in Earth's history. There are four main types of sediment: lithogenous composed of rock fragments, biogenous composed of organism remains, hydrogenous formed by precipitation of dissolved materials, and cosmogenous derived from outer space. Biogenous oozes, formed from silica- or calcium carbonate-secreting organisms, accumulate in different regions depending on surface water temperature and depth. Ocean sediments contain valuable resources and provide insights about Earth's past.

1. Chapter 5
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. Collecting ocean sediment
Specially
designed ships
collect cores by
rotary drilling
Cores allow
scientists to
analyze ocean
sediment

4. 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

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

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

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

8. 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

9. 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

10. Biogenous sediment composition
Microscopic biogenous tests are
composed of 2 main chemical compounds:
1. Silica (SiO2) including opal (SiO2 · nH2O)
Diatoms (algae)
Radiolarians (protozoan)
1. Calcium carbonate or calcite (CaCO3)
Coccolithophores (algae)
Foraminifers (protozoan)

11. Examples of silica-secreting
microscopic organisms
Diatom Radiolarian

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

13. Examples of calcite-secreting
microscopic organisms
Coccolithophores Foraminifers

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

15. 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 Chalk cliffs of southern England
ooze)

16. 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)

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

18. 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

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

20. 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

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

22. 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 Microscopic
cosmogenous
proportion of ocean sediment spherule

23. 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

24. Worldwide distribution of neritic
and pelagic sediment

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

26. End of Chapter 5