1. CHAPTER 4 Marine Sediments
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2. Chapter Overview Marine sediments contain a record of Earth history.
Marine sediments provide a variety of important resources.
Marine sediments have a variety of origins.
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3. Marine Sediments Eroded rock particles and fragments
Transported to ocean
Deposit by settling through water column
Oceanographers decipher Earth history through studying sediments.
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4. Paleoceanography and Marine Sediments
Paleoceanography – study of how ocean, atmosphere, and land interactions have produced changes in ocean chemistry, circulation, biology, and climate
Marine sediments provide clues to past changes.
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5. Marine Sediment Classification
Classified by origin
Lithogenous – derived from land
Biogenous – derived from organisms
Hydrogenous or Authigenic – derived from water
Cosmogenous – derived from outer space
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6. Marine Sediments (table 4.1)
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7. Lithogenous Sediments
Eroded rock fragments from land
Also called terrigenous
Reflect composition of rock from which derived
Produced by weathering
Breaking of rocks into smaller pieces
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8. Lithogenous Sediments
Small particles eroded and transported
Carried to ocean
Streams
Wind
Glaciers
Gravity
Greatest quantity around continental margins
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9. Lithogenous Sediment Transport
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10. Lithogenous Sediments
Reflect composition of rock from which derived
Coarser sediments closer to shore
Finer sediments farther from shore
Mainly mineral quartz (SiO2)
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11. Lithogenous Quartz and Wind Transport
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12. Grain Size Proportional to energy of transportation and deposition
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13. In your homework groups, discuss these points in reference to sediment particle sizes.
For sediment originating on land (terrestrial sediment), what sediment size in general would you expect to find deposited closer to shore?
Why can finer-sized sediment be found far from land?
What are several ways in which large particles, even boulders, can be transported and deposited on the ocean floor far from land?

14. Settling of sedimentary materials
Diameter
Rate of settling in sea water
Distance traveled in sinking 1,000 m with current of 1 cm/sec
Very fine sand (0.1mm)
1472 cm/hr
2.4 km
Silt (0.05 mm) 31
116 km
Clay (0.001 mm)
0.147
24,500 km

15. Large sediment, including boulders, can be found far from sea due to:
The previous chart shows how very fine sediment such as clay can travel very long distances from its source before settling to the ocean floor.
Coarse sediment tends to be deposited in large quantity close to shore.
Large sediment, including boulders, can be found far from sea due to:
Being carried by glacial icebergs (ice rafting).
Being carried in root mass of floating trees.
Dumping of dredged material.
Meteorites
Very large submarine landslides
other?

16. Sediment Texture Grain size sorting Textural maturity
Indication of selectivity of transportation and deposition processes
Textural maturity
Increasing maturity if
Clay content decreases
Sorting increases
Non-quartz minerals decrease
Grains are more rounded (abraded)
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17. Sediment Distribution
Neritic
Shallow-water deposits
Close to land
Dominantly lithogenous
Typically deposited quickly
Pelagic
Deeper-water deposits
Finer-grained sediments
Deposited slowly
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18. Neritic Lithogenous Sediments
Beach deposits
Mainly wave-deposited quartz-rich sands
Continental shelf deposits
Relict sediments
Turbidite deposits
Graded bedding
Glacial deposits
High latitude continental shelf
Currently forming by ice rafting
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19. Pelagic Deposits Fine-grained material
Accumulates slowly on deep ocean floor
Pelagic lithogenous sediment from
Volcanic ash (volcanic eruptions)
Wind-blown dust
Fine-grained material transported by deep ocean currents
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20. Pelagic Deposits Abyssal Clay
At least 70% clay sized particles from continents
Red from oxidized iron (Fe)
Abundant if other sediments absent
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21. Biogenous Sediment Two major types: Mainly algae and protozoans
Hard remains of once-living organisms
Two major types:
Macroscopic
Visible to naked eye
Shells, bones, teeth
Microscopic
Tiny shells or tests
Biogenic ooze
Mainly algae and protozoans
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22. Biogenous Sediment Composition
Two most common chemical compounds:
Calcium carbonate (CaCO3)
Silica (SiO2 or SiO2·nH2O)
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23. Silica in Biogenous Sediments
Diatoms
Photosynthetic algae (autotrophs)
Diatomaceous earth (diatomite)
Radiolarians
Protozoans
Use external food (heterotrophs)
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24. Silica in Biogenous Sediments
Tests from diatoms and radiolarians generate siliceous ooze.
Siliceous ooze lithifies into diatomaceous earth.
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25. Calcium Carbonate in Biogenic Sediments
Coccolithophores
Also called nannoplankton
Photosynthetic algae
Coccoliths – individual plates from dead organism
Chalk
Lithified coccolith-rich ooze
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26. Calcium Carbonate in Biogenic Sediments
Foraminifera
Protozoans
Use external food
Calcareous ooze
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27. Distribution of Biogenous Sediments
Depends on three processes:
Productivity (forming)
Destruction (losing)
Dilution (maximizing or minimizing)
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28. Neritic Deposits
Dominated by lithogenous sediment, may contain biogenous sediment
Carbonate Deposits
Carbonate minerals containing CO3
Marine carbonates primarily limestone – CaCO3
Most limestones contain fossil shells
Suggests biogenous origin
Ancient marine carbonates constitute 25% of all sedimentary rocks on Earth.
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29. Carbonate Deposits Stromatolites Fine layers of carbonate
Warm, shallow- ocean, high salinity
Cyanobacteria
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30. Calcareous Ooze and the CCD
CCD – Calcite compensation depth
Depth where CaCO3 readily dissolves
Rate of supply = rate at which the shells dissolve
Warm, shallow ocean saturated with calcium carbonate
Cool, deep ocean undersaturated with calcium carbonate
Lysocline – depth at which a significant amount of CaCO3 begins to dissolve rapidly
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31. Calcareous Ooze and the CCD
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32. Calcareous Ooze and the CCD
Scarce calcareous ooze below meters (16,400 feet) in modern ocean
Ancient calcareous oozes at greater depths if moved by sea floor spreading
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33. Sea Floor Spreading and Sediment Accumulation
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34. Distribution of Modern Calcium Carbonate Sediments
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35. Hydrogenous Marine Sediments
Minerals precipitate directly from seawater
Manganese nodules
Phosphates
Carbonates
Metal sulfides
Small proportion of marine sediments
Distributed in diverse environments
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36. Manganese Nodules
Fist-sized lumps of manganese, iron, and other metals
Very slow accumulation rates
Many commercial uses
Unsure why they are not buried by seafloor sediments
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37. Distribution of Manganese Nodules
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38. Phosphates and Carbonates
Phosphorus-bearing
Occur beneath areas in surface ocean of very high biological productivity
Economically useful as fertilizer
Carbonates
Aragonite and calcite
Oolites
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39. Metal Sulfides Metal sulfides Contain:
Iron
Nickel
Copper
Zinc
Silver
Other metals
Associated with hydrothermal vents
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40. Evaporites Evaporites Minerals that form when seawater evaporates
Restricted open ocean circulation
High evaporation rates
Halite (common table salt) and gypsum
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41. Cosmogenous Marine Sediments
Macroscopic meteor debris
Microscopic iron- nickel and silicate spherules (small globular masses)
Tektites
Space dust
Overall, insignificant proportion of marine sediments
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42. Marine Sediment Mixtures
Usually mixture of different sediment types
Typically one sediment type dominates in different areas of the sea floor.
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43. Pelagic and Neritic Sediment Distribution
Neritic sediments cover about ¼ of the sea floor.
Pelagic sediments cover about ¾ of the sea floor.
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44. Pelagic and Neritic Sediment Distribution
Distribution controlled by
Proximity to sources of lithogenous sediments
Productivity of microscopic marine organisms
Depth of water (example: CCD)
Sea floor features(example: trench)
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45. Pelagic Sediment Types
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46. Sea Floor Sediments Represent Surface Ocean Conditions
Microscopic tests sink slowly from surface ocean to sea floor ( years)
Tests can be moved far away horizontally (recall how far tiny particles can move while slowly settling)
Most biogenous tests clump together in fecal pellets
Fecal pellets large enough to sink quickly (10-15 days)
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47. Worldwide Marine Sediment Thickness
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48. Resources from Marine Sediments
Energy resources
Petroleum
Mainly from continental shelves
Gas hydrates
Sand and gravel (including tin, gold, and so on contained within)
Evaporative salts
Phosphorite
Manganese nodules and crusts
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49. Mining Sea Salt
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50. Dwarves who work the mine Salt mine under Detroit, MI
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51. End of CHAPTER 4 Marine Sediments
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