1. Marine
Sediments

2. Sediment Classification
All sediment classification is based on…
Gravel, Sand, Silt, Clay
1.Grain Size
2.Angularity
3.Sorting
Roundedness of the grains
4.Composition
Distribution of the grain sizes
What minerals or chemicals

3. Grain Size
Gravel
Sand
Silt
Clay
Silt + Clay = Mud 

4. Four Types of Marine Sediments
Lithogenous Sediment
Biogenous Sediment
Hydrogenous Sediment
Cosmogenous Sediment

5. Lithogenous Sediment Origins ~ Weathering of continental rocks
Also from volcanoes  volcanic ash

6. Lithogenous Sediment Composition ~ Composed primarily of quartz
Continental crust is primarily composed of granite….
mica, amphibole and orthoclase weather and erode quickly leaving behind quartz
Quartz
Mica
Amphibole
Orthoclase

7. Lithogenous Sediment
Texture
Wentworth Scale – Grain Size

8. Lithogenous Sediment Distribution ~ Categorized as either…. Neritic
Pelagic
Found on the continental shelf or shallow water near islands
- coarser-grained
Found in deep ocean basins
- Finer-grained

9. Lithogenous Sediment Neritic Sediment Beach Deposits Glacial Deposits
Turbidity Deposits – underwater avalanche down the continental slope
Continental Shelf Deposits

10. Lithogenous Sediment Pelagic Sediment – Abyssal Clay
70% clay sized particles
Transported by wind or ocean currents
Contained oxidized iron  red clays

12. Macroscopic Biogenous Sediment
Origins
Macroscopic Biogenous Sediment
Microscopic Biogenous Sediment
Tests – small shells
Produce oozes – fine-grained mushy material
Bones, shells, teeth
Organisms contributing the most are algae and protozoans

13. Biogenous Sediment Composition – Two Types Calcium Carbonate – CaCO3
Silica – SiO2

14. Coral Reefs: reefs grow in shallow water; carbonate skeletons of coral and cemented debris

15. Calcareous Oozes – eventually form chalk or limestone
Coccolithithophores (algae)
Foraminifera
(protozoan)
Chalk – White Cliffs of Dover
Distribution Related to Chemistry
Solubility Increases with
- lower pH
- higher pressure
- low temperatures

16. Carbonate Compensation Depth
Distribution tends to be in fairly “shallow” areas
CCD = Carbonate Compensation Depth
Level at which CaCO3 precip = dissolution
Below CCD, no calcareous sediments
Forms visible “snowcap” of sediments

17. Carbonate Compensation Depth
Associated with mid-ocean ridges
In Atlantic Ocean, CCD about 4000m
In N. Pacific, CCD about 500m (due to poor circulation!)
In S. Pacific, CCD about 2500m

18. Siliceous Oozes consist of >30% SiO2 shells
Radiolarian - plankton
Diatoms - plankton
Heterotrophs
Love warm water
Found in the Equitorial Pacific
Distribution is related to the biology of the organism……
Photosynthesis
Found of cold water
Lots of light and nutrients
High latitudes

19. Biogenous Sediment Distribution – most common pelagic sediment
White Cliffs of Dover – Former deep ocean
Stromatilites - Neritic

21. Hydrogenous Sediment
Origins Chemical reactions within the seawater cause minerals to precipitate out of solution
Types of Hydrogenous Sediments
Managanese Deposits
Phosphate Deposits
Halite Deposits
Sources of dissolved minerals vary – submerged rock, new crust formation, hydrothermal vent water, river runoff
No pattern to distribution!

22. Hydrogenous Sediment Manganese Deposits Deep-ocean floor
Manganese oxide (30%) and Iron oxide (20%)
Areas of strong, deep ocean currents and little sedimentation

23. Hydrogenous Sediment Halite Deposits Area of high evaporation
Mediterranean Sea

25. Cosmogenous Sediment Origins~ Composition~ Come from Outer Space
Cosmic dust and occasional impacts from asteroids or comets
Represent a very small percent of sediment on the ocean floor

26. Cosmogenous Sediment Two Types~ Meteor Debris Spherules
Others composed of iron and nickel from asteroid belt collisions
Meteor Debris
Spherules
Tektites - Come from silicate rock produced from impact event (macro or micro)

27. All sediment is classified based on the following factors…
A. Sorting
B. Composition
C. Angularity
D. All of the above

28. A sediment that is derived from continental sources is known as
A. Biogenous
B. Lithogenous
C. Cosmogenous
D. Hydrogenous

29. ____________ sediment accounts for smallest percentage of sediment on the ocean floor.
A. Biogenous
B. Lithogenous
C. Cosmogenous
D. Hydrogenous

30. Manganese Nodules are an example of
A. Biogenous
B. Lithogenous
C. Cosmogenous
D. Hydrogenous

31. What factors influence the distribution of calcareous oozes?
A. temperature
B. pH
C. pressure
D. All of the above

32. In the Atlantic Ocean, the Carbonate Compensation Depth (CCD) can be found around
A meters
B. 500 meters
C meters
D meters

33. Siliceous deposits tend to dominate below the CCD because
A. Calcareous organisms cannot live that deep
B. Siliceous organisms are more productive below the CCD
C. At or below the CCD, calcareous material dissolves as quickly as it accumulates
D. Marine organisms consume them

34. Sediment Transport and Deposition
Clay and Gravels are the hardest to erode.
- gravels are heavy
- clay held together by surface tension
When sediments deposit, largest particles settle first and smallest are last.
transportation

35. Sediment Deposition: From Continental Shelf to Ocean Deep
Historical Geology Notes: Sedimentary Environments
Stanley, Earth System History, 2nd ed.
Sediments that reach the ocean may be deposited in a delta which is in many ways like an underwater alluvial fan. Sediments are distributed in a fan-shaped body that grows outward (seaward) with time. Longshore currents will transport sediments along the coast.
All along a coast, sediments derived from longshore drift and sediments formed in place from wave action are distributed by wave energy. Wave action is strongest at the ocean surface and decreases with depth in the water down to a depth of half the wavelength (L/2). Because of this, in shallow water near the shore the fine sediments are washed away as suspended load. Only coarse sediments are deposited in shallow water. As the depth to the bottom increases, the bottom is stirred less and less by wave action; progressively finer sediments can be deposited in increasingly deeper water. Deposited sediments progress from sands near the shore to silts and clays farther offshore. In cool or turbid (murky) water, fine sediments will dominate to the edge of the continental shelf.
In warm tropical waters, if most of the fine sediments have already been deposited, coral reefs will grow in shallow water on the continental shelf. Modern coral reefs do not form in the deep ocean abyss where there is no light because symbiotic algae that lives in the coral needs light to grow. Coral reefs also do not grow in turbid nearshore waters where terrestrial sediments have not yet been deposited. In a sedimentary sequence, alternating sandstone, shale, and limestone generally indicates a marine environment. Almost all limestone is deposited in the ocean. The sandstones and shale would contain fossils of marine organisms. The shales would almost certainly have no mudcracks.
The continental shelf is the shallow ocean surrounding the continent. The depth at the edge of the shelf is usually not more than 100 to 150 meters (the length of one to one-and-a-half football fields). Some sand and mud are carried to the edge of the continental shelf via submarine canyons which are like undersea river valleys. Sediments build up at the edge of the shelf and when too much has accumulated these flow down the continental slope and rise as turbidity currents (like underwater mud flows). The resulting deposits, called turbidites, contain some chaotic, poorly sorted coarse layers at their base and then finer layers on top. Repeated sequences of turbidites indicate deposition on the continental slope and continental rise.
Sedimentation on the shelf is more rapid than in the deep ocean

36. Sedimentation Processes on the Continental Shelf
Tides, waves, and currents strongly affect continental-shelf sedimentation.
Mix of both biogenous and lithogenous sediment.

37. Continental-Shelf Sedimentation Rates
Vary by Region….
At the mouths of large rivers, sedimentation can occur at a rate of one meter per thousand years, but there’s a lot of variation.

38. From Continental Shelf to Abyssal Plain….
Sediments can be transported from the continental shelf down the continental slope by turbidity currents.
A turbidity current is an underwater avalanche of sediment.

39. Sedimentation Processes on the Deep-Ocean Bottom
Vary by Region….
Deep-ocean sediments tend to be high in biogenous material.
Lithogenous sediments, except for clays, are generally confined near shore.

40. The thickness of sediments in the deep ocean also varies with topography.
Sediments are thickest on the abyssal plains and thinnest or absent on the mid-ocean ridges and seamounts.

41. calcareous oozes (carbonate) accumulates in shallower areas of the deep sea, along mid-ocean ridges,
siliceous oozes accumulate in cold water areas (around Antarctica and off the coast of Alaska) and
siliceous oozes accumulate where there is a source of rich nutrients (along the equator in the Pacific Ocean)

42. Fecal Pellets
Scientists find that bottom composition is usually similar to the particle composition of the water above it. This is due to fecal pellets.
Large planktonic organisms, like copepods, consume the calcareous or silicone organisms that also dominate the bottom ooze. These large organisms eliminate their waste as dense fecal pellets of multiple skeletal and shell remains compressed together. These dense pellets sink quickly and the decomposition process begins.

43. What can sediments be used for?

44. Mineral Nodules
Minerals nodules are hydrogenous sediments produced by chemical precipitation very slowly. Biological processes might be involved.
Nodules grow at a rate of about 1 to 200 millimeters (.039 to 7.9 inches) per million years.

45. Mineral Nodules
Ferromanganese nodules consist of iron and manganese found over as much as 50% of the deep Pacific floor.
Phosphorite nodules consist of phosphorite and other trace minerals found on the shallow banks and continental shelves off California, Argentina and Japan.

46. Petroleum and Natural Gas
Oil and natural gas found under the ocean contribute $125 billion in annual revenues. More than a third of the world’s crude petroleum and a quarter of its natural gas come from sedimentary deposits on the continental shelf.

47. Other Sediments With Economic Importance
Metal sulfide deposits found at deep-sea hydrothermal vents are rich and vast enough (especially in the Red Sea) that mining them could be economically feasible.
Evaporites form at the surface and comprise the salts left behind when seawater evaporates. They are a source of calcium carbonate, calcium sulfate, gypsum and sodium chloride.
Sand and gravel are an important resource for the construction industry accounting for $500 million yearly.

48. How do we study sediment?

49. Sediment Study Tools and Techniques
Techniques and tools to study ocean sediments include:
Clamshell sampler – collects a large sample of the top sediment.
Piston corer – used to collect different sediment layers as deep as 25 meters (82 feet) into the ocean bottom.
Specialized vessels with drilling equipment – used to produce sediment core samples of 500 meters (1,640 feet) long.
Seismic tools – transmit sounds that travel through water and into sediment. Different sediment layers create distinct echoes. Used when looking for oil or natural gas.

50. Studying sediments gives us information about….
Previous Ocean Currents Atmospheric Conditions
Changes in Sea Level Climatic Changes
Biological Productivity Trends

51. Stratigraphy
Study of sediment layers
Scientists use deep-sea stratigraphy to look for clues, such as rock composition, microfossils, deposition patterns and other physical properties.
Based on these they can estimate the age of the sediment layers and draw conclusions about the past.

52. Paleoceanography Study of prehistoric oceans…
Ongoing research of the Earth’s ancient climate currently emphasizes deep-ocean sediments called siliceous oozes.
Oceanographers have played a key role in helping develop current theories that propose that Mars once had oceans.

53. True/False: Sedimentation is more rapid on the continental shelf than in the deep-ocean
A. True
B. False

54. Deep-ocean sediments tend to have proportionately ____ biogenous sediment than continental-shelf sediment.
A. less
B. more

55. The predominate mechanism of transporting lithogenous sediment from the continental shelf to the ocean-deep is
A. Turbidity current.
B. wind.
C. Ocean currents.
D. waves.

56. A. small particles actually sink more quickly than large particles.
Deep-ocean sediment tends to have the same particle composition as the surface water above it because
A. small particles actually sink more quickly than large particles.
B. surface water is made primarily of deep water.
C. Fecal pellets of large plankton carry materials quickly to the bottom.
D. All of the above.

57. The tool used primarily of petroleum exploration is
A. Clam sampler
B. drilling
C. Piston corer.
D. seismic.

58. Studying ocean sediments can provide us information about
A. Climatic changes
B. Past ocean currents
C. Piston corer.
D. Seismic tools.