1. CHAPTER 4: Marine Sediments
Fig. CO-4

2. Marine sediments Eroded rock particles and fragments
Oceanographers decipher Earth history through studying sediments

3. Sediment Origins
Sediments may be classified by origin based on four categories.
1. Lithogenous sediments – Come primarily from l_________ e_________ carrying particles into the sea or from v__________ e__________. These are the majority of sediments.
Quartz and clay are the two most common materials along with feldspar. Volcanic islands contribute sediments of basalt and other volcanic materials.
2. Biogenous sediments – Originate from L_________ O___________ and cover a large areaof the seafloor.
S_________ and c_________c_____________ are the materials that come from shells and hard skeletons of planktonic organisms.
3. Hydrogenous sediments – Result from c_________ r________ within seawater
Minerals come out of solution and form particles that settle on the bottom.
Produces ferromanganese and phosphorite nodules.
Sources of dissolved minerals vary – submerged rock, new crust formation, hydrothermal vent water, river runoff.
4. Cosmogenous sediments – Come from o________ s_________ consisting of cosmic dust and occasional impacts from asteroids and comets.
They settle through the air as the others do through water. About 15,000-30,000 metric tons of space dust settle on the Earth each year; least abundant of the sediments.
Types of Sediment
Chapter 12 Pages to 12-13

4. Lithogenous sediments
Fig. 4.5

5. Lithogenous sediments
Most lithogenous sediments at continental margins
Coarser sediments closer to shore
Finer sediments farther from shore
Mainly mineral quartz (SiO2)

6. Sediment Sizes
Sediments are classified on grain size – the diameter of the particle. Most sediments are composed of three sizes
1. Smallest= = = 4. 5. 6. 7.
Decomposed organic matter=
Grain size and current velocity affect the deposition and erosion of sediment.
Types of Sediment
Chapter 12 Pages to 12-15

7. Distribution of sediments
Neritic
Shallow water deposits
Close to land
Dominantly lithogenous
Typically deposited quickly
Pelagic
Deeper water deposits
Finer-grained sediments
Deposited slowly

8. Lithogenous sediments
Sources of material:
V_______ ash (volcanic eruptions)
Eroded M_________
W________-b_________ dust
Fine-grained material transported by deep ocean currents
Abyssal clay (red clay)
Oxidized iron

9. Biogenous marine sediments
Hard remains of once-living organisms
S_______, b______, teeth, and diatom _____________
Tiny shells or tests settle through water column
Biogenic ooze (30% or more tests)
Mainly algae and protozoans

10. Biogenous marine sediments
either calcium carbonate (CaCO3)
or silica (SiO2 or SiO2·nH2O)

11. Silica in biogenic sediments
Diatoms (algae)
Photosynthetic
Diatomaceous earth
Radiolarians (protozoans)
Use external food
Siliceous ooze
Fig. 4.7a
Fig. 4.7b

12. Siliceous ooze Seawater undersaturated with silica
Siliceous ooze commonly associated with high biologic productivity in surface ocean
Fig. 4.11

13. Calcium carbonate in biogenous sediments
Coccolithophores (algae)
Photosynthetic
Coccoliths (nano-plankton)
Rock chalk
Fig. 4.8a

14. Calcium carbonate in biogenous sediments
Foraminifera (protozoans)
Use external food
Calcareous ooze
Fig. 4.8c

15. Calcareous ooze and the CCD
Fig. 4.13
Scarce calcareous ooze below 5000 m in modern ocean
Ancient calcareous oozes at greater depths if moved by sea floor spreading

17. Hydrogenous marine sediments
Minerals precipitate directly from seawater
Manganese nodules
Phosphates
Carbonates
Metal sulfides
Small proportion of marine sediments
Distributed in diverse environments

18. Iron-manganese nodules
Fist-sized lumps of manganese, iron, and other metals
Very slow accumulation rates
Why are they on surface sea floor?
Fig. 4.15a

19. Hydrogenous marine sediments
Phosphates
Phosphorus-bearing
Occur beneath areas in surface ocean of very high biological productivity
Economically useful: fertilizer
Carbonates
Aragonite and calcite
Oolites

20. Hydrogenous marine sediments
Metal sulfides
Contain iron, nickel, copper, zinc, silver, and other metals
Associated with hydrothermal vents
Evaporites
Minerals that form when seawater evaporates
Restricted open ocean circulation
High evaporation rates
Halite (common table salt) and gypsum

21. Cosmogenous marine sediments
Macroscopic meteor debris
Microscopic iron-nickel and silicate spherules
Tektites
Space dust
Overall, insignificant proportion of marine sediments

23. Marine sediments often represent ocean surface conditions
N_________ supply
Abundance of marine life
A__________ winds
Ocean c__________ patterns
V__________ eruptions
Major extinction events
Changes in c___________
Movement of t________ plates

24. How Scientists Study Sediments
Techniques and tools to study ocean sediments include:
Clamshell sampler –
Piston corer –
Drilling vessels –
Seismic tools –
The Study of Sediments
Chapter 12 Pages 12-3 to 12-6

25. Resources from marine sediments
Energy resources
Petroleum
Mainly from continental shelves
Gas hydrates
Sand and gravel (including tin, gold, and so on)
Evaporative salts
Phosphorite
Manganese nodules and crusts

26. Salt deposits
Fig. 4.26

27. Manganese nodules
Fig. 4.27

28. End of CHAPTER 4 Marine Sediments
Fig. 4E