1. Geologic Oceanography
Sediments
Geologic Oceanography

2. What are Sediments? Particles entering the ocean Accumulate
Rapidly on continental margin (neritic)
Slowly in the deep ocean (pelagic)
Reflect ocean history

3. Types of Marine Sediments
Sediment may be classified in two ways:
By grain size
By origin

4. Types of Marine Sediments
Types of Marine Sediments by grain size:
Boulder
>256 mm
Cobble mm
Pebble mm
Granule
2 - 4 mm
Sand
1/ mm
Silt
1/ /16 mm
Clay
<1/256

5. Types of Marine Sediments
Types of Marine Sediments by grain size:
Small
Large
Move
Low – moderate
High
Deposit
Very quiet
Low - moderate

6. High energy Low energy Low energy Still water
Energy needed to move particle
- Boulder
- Cobble
- Pebble
- Gravel
- Course sand
- Medium sand
- Fine sand
- Silt
- Clay
- Boulder
- Cobble
- Pebble
- Gravel
- Course sand
- Medium sand
- Fine sand
- Silt
- Clay
Energy needed to deposit particle
Low energy
Still water

7. Types of Marine Sediments
Types of Marine Sediments by grain size:

8. Types of Marine Sediments
Sediment can also be classified according to its source.
Lithogenous
Biogenous
Hydrogenous / Chemical precipitates
Cosmogenous

9. Types of Marine Sediments
Lithogenous Sediments
Sediments from terrestrial (land) sources
Includes
Sands and muds from continental margins
Glacial deposits
Clays

10. Types of Marine Sediments
Lithogenous Sediments
Red Clay
Found in low productivity areas
Low sedimentation rates
Wind-blown sediment

11. Types of Marine Sediments
Biogenous Sediments
particles derived from hard parts and soft tissues of organisms
Ooze = greater than 30% biogenous sediment
Distribution related to:
sediment supply
rate of dissolution
and sediment dilution

12. Biogenous Sediment Accumulation
Thurman Essentials of Oceanography 6/e fig 4.15
Relationships among carbonate compensation depth, the mid-ocean ridge, sea floor spreading, productivity, and destruction allow calcareous ooze to be found below the CCD.
Thurman Essentials of Oceanography 6/e fig 4.15

13. Types of Marine Sediments
Biogenous Sediments
Siliceous Oozes
Fine-grained pelagic deposit
Composition:
30% siliceous (SiO2) material of organic origin
Diatoms (phytoplankton) and Radiolaria (zooplankton)
Siliceous particles dissolve more slowly than calcareous particles
siliceous ooze
Fine-grained pelagic deposit of the deep-ocean floor with more than 30% siliceous material of organic origin. Radiolaria and diatom remains are the major constituents of the siliceous oozes, which tend to occur at depths in excess of 4500 m.
A Dictionary of Earth Sciences, © Oxford University Press 1999 (

14. Siliceous Oozes Thurman Essentials of Oceanography 6/e
Siliceous ooze accumulates on the ocean floor beneath areas of high productivity, where the rate of accumulation of siliceous tests is greater than the rate at which silica is being dissolved.

15. Diatoms Composed of SiO2 Phytoplankton Base of food chain

16. Radiolaria Composed of SiO2 Zooplankton Base of food chain

17. Types of Marine Sediments
Biogenous Sediments
Calcareous Oozes
Wide-spread in relatively shallow areas of the deep sea
CaCO3 particles dissolve at “Carbonate Compensation Depth” = (CCD)
Atlantic: ~ 4,000 m
Pacific: ~ ,500 m

18. Foraminifera
Composed of calcium carbonate (CaCO3)
Zooplankton

19. Types of Marine Sediments
Hydrogenous sediments
Minerals that crystallize directly from seawater
Most common types include
Manganese nodules
Calcium carbonates
Metal sulfides
Evaporites
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.

20. Types of Marine Sediments
Hydrogenous sediments
Ferromanganese Nodules
First discovered in 1868 on the Kara Sea (Russia)
Characteristics
small balls (lightly flattened)
dark-brown
and cm in diameter
Found at depths of 4,000 to ,000 m
Not clear how these nodules form

21. Distribution Of Manganese Nodules
Thurman Essentials of Oceanography 6/e fig 4.23
This generalized map shows the distribution of manganese nodules on the sea floor. After Cronan, D. S Deep sea nodules: Distribution and geochemistry, in Glasby, G. P., ed., Marine Manganese Deposits, Elsevier Scientific Publishing Co.

22. Sulfide Deposits
EARTH: An Introduction to Physical Geology 7th ed / Tarbuck & Lutgens fig 21.25
Massive sulfide deposits can result from the circulation of seawater through the oceanic crust along active spreading centers. As seawater infiltrates the hot basaltic crust, it leaches sulfur, iron, copper, and other metals. The hot, enriched fluid returns to the seafloor near the ridge axis along faults and fractures. Some metal sulfides may be precipitated in these channels as the rising fluid begins to cool. When the hot liquid emerges from the seafloor and mixes with cold seawater, the sulfides precipitate to form massive deposits.

23. Types of Marine Sediments
Hydrogenous sediments
Evaporites
Evaporation triggers deposition of chemical precipitates
rock salt
rock gypsum

24. Formation of Evaporites

25. Astronaut photo of the southwestern edge of the Zagros Mountains featuring salt domes (the white section in the middle and the bump on the left).
Astronaut photo of the southwestern edge of the Zagros Mountains featuring salt domes (the white section in the middle and the bump on the left).
Source
Date February 28, 2006
Author NASA
Permission US government, public domain
Source

26. Salt Ponds, S. San Francisco Bay
(Earth Sciences and Image Analysis Laboratory at Johnson Space Center )

27. Death Valley, California
Once a deep Pleistocene Lake (100 miles long feet deep)
Change in climate at end of ice age
NASA images created by Jesse Allen, Earth Observatory, using data obtained courtesy of the MODIS Rapid Response team and the Goddard Earth Sciences DAAC.

28. Wieliczka Salt Mine, Poland
Photo date 9/97; © by J.S. Aber
Great cathedral, a large chamber carved entirely within salt, including floor,
walls, ceiling, and decorations. Chandeliers are made with salt crystals.
Photo date 9/97; © by J.S. Aber
Closeup view of the cathedral's altar.

29. Wieliczka Salt Mine Virtual Tour
St. Anthony’s Chapel, built between
St. John Chapel built ~1859

30. Types of Marine Sediments
Organic Matter
Oxidized Sediments
Slow burial, organic matter will oxidize and produce water + carbon dioxide
Find burrows = life = oxygen
Oxidized mud = olive greenish gray
Unoxidized Sediments
Rapid burial, little time for oxidation
Unoxidized mud = black

31. Types of Marine Sediments
Organic Matter
Weight of overlying sediment plus increase temperature - cook organic matter = petroleum
Usually if black have lots of organic matter

32. Sediment distribution
Sand
Closer to shore, on margins of continents
Brought to margins by by rivers
Sand requires high energy to transport
Waves rework sand along coast to form our beaches
Some sand makes it to deep ocean through submarine canyons

33. Sediment distribution
Clays & Silts
Finer sediments are suspended in water
Carried by the currents until they settle out of the water
Found in deep ocean, low energy environments

34. Sediment distribution
Where are sediments the thickest?
Thickest in trenches—Accumulations may approach 10 kilometers
Basins
Pacific Ocean—About 600 meters or less
Atlantic Ocean—From 500 to 1000 meters thick
Thinnest along spreading centers
Mud is the most common sediment on the deep-ocean floor

37. Sediment distribution
Types of deep-ocean basin sediments
Turbidites – deposits made by turbidity currents
Oozes – deep-ocean sediment containing at least 30% biogenous material
Hydrogenous sediments - originate from chemical reactions that occur in the existing sediment
Evaporites - salts that precipitate as evaporation occurs
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.

38. Sediment distribution
Rates Of Deposition
Deep ocean cm/1000 yrs
slow rates yet can get thick because oldest crust is 200 m.y.
clays take 100 yrs to sink 3000 m

39. Studying Sediments How do scientists study sediments?
Deep-water cameras
Clamshell samplers
Dredges
Piston Corers
Core libraries
Seismic profilers
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.

40. Studying Sediments Dredges
Rock samples being removed from a small rock dredge.
Scientists inspect a just recovered dredge haul (below), which contains samples of volcanic basalt (above left) and a seafloor crust rich in manganese (above right).

41. Studying Sediments
One method of studying sediments uses a clamshell sampler. The sampler can be used to obtain a relatively undisturbed sediment sample.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.

42. Van – Veen Mud Grab

43. Studying Sediments Grab Sampler
Good for collecting soft sediment, sand or perhaps gravel.
Low tech - basically just a weighted cage that is dragged along the sea floor.

44. Studying Sediments Piston Corer
Allows a cylinder of sediment to be taken for analysis to determine the age of the material, as well as the density, strength, molecular composition and radioactivity of the sediment.
Used by research vessels such as the JOIDES Resolution
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.

45. Piston Corer

46. Drilling Ocean Cores
EARTH: An Introduction to Physical Geology 7th ed /
JOIDES Resolution can reenter holes years after initial drilling.

47. Corer This figure shows an examination of deep- ocean sediment cores.
Long cylinders of sediment and rock called cores are cut in half and examined, revealing interesting aspects of Earth history. APT photo

48. Studying Sediments What can scientists learn by studying sediments?
Historical information
Location of natural resources, especially crude oil and natural gas
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.

49. Studying Sediments
Based on data from core samples, scientists have determined the age of portions of the Pacific floor, measured in mega-annums, or millions of years.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.

50. Seabed Resources Depletion of onshore resources - need alternatives
Sand & Gravel
Phosphorite
Sulfur
Coal
Oil and Gas

51. How Much Do We Need?

52. EARTH: An Introduction to Physical Geology 7th ed / Tarbuck & Lutgens fig 21.2
The annual per capita consumption of nonmetallic and metallic mineral resources for the United States is nearly 10,000 kilograms (11 tons)! About 94 percent of the materials used are nonmetallic. (After U.S. Bureau of Mines)

53. Hydrocarbon Seeps Thurman Essentials of Oceanography 6/e fig 15.28a
Hydrocarbon seeps on the continental slope of the Gulf of Mexico

54. Gas Hydrate
Formed from a mixture of water and natural gas, usually methane.
Occurs in the pore spaces of sediments
Gas Hydrate is an ice-like crystalline solid formed from a mixture of water and natural gas, usually methane. They occur in the pore spaces of sediments, and may form cements, nodes or layers.
Gas Hydrate is found in sub-oceanic sediments in the polar regions (shallow water) and in continental slope sediments (deep water), where pressure and temperature conditions combine to make it stable.
Natural Gas Hydrate contains highly concentrated methane, which is important both as an energy resource and as a factor in global climate change.

55. ~ End ~