1. CHAPTER 4: Marine Sediments at ECC
Dr. C. Dong 03/16/10
CHAPTER 4: Marine Sediments at ECC
Dr. C. Dong

2. Marine sediments Eroded rock particles and fragments
Dr. C. Dong 03/16/10
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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3. Classification of marine sediments
Dr. C. Dong 03/16/10
Classification of marine sediments
Classified by origin
Lithogenous (derived from land)
Biogenous (derived from organisms)
Hydrogenous (derived from water)
Also known as Authigenic
Cosmogenous (derived from outer space)
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4. Features of marines sediments
Dr. C. Dong 03/16/10
Features of marines sediments
Origin
Distribution
Texture
Composition
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5. Distribution of sediments
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Distribution of sediments
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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6. Distribution of neritic and pelagic marine sediments
Dr. C. Dong 03/16/10
Distribution of neritic and pelagic marine sediments
Neritic sediments cover about ¼ of sea floor
Pelagic sediments cover about ¾
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7. Distribution of neritic and pelagic marine sediments
Dr. C. Dong 03/16/10
Distribution of neritic and pelagic marine sediments
Fig. 4.19
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8. Lithogenous Sediments Origin
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Eroded rock fragments from land
Reflect composition of rock from which derived
Transported from land by
Water (e.g., river-transported sediment)
Wind (e.g., windblown dust) - aolian transport
Ice (e.g., ice-rafted rocks)
Gravity (e.g., turbidity currents)
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9. Lithogenous Sediments Texture
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Lithogenous Sediments Texture
Fig. 4.5
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10. Sediment texture Grain size
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Sediment texture
Grain size
Proportional to energy of transportation and deposition
Table 4.2
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11. Lithogenous Sediments Distribution
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Lithogenous Sediments Distribution
Most lithogenous sediments at continental margins
Coarser sediments closer to shore
Finer sediments farther from shore
Mainly mineral quartz (SiO2)
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12. Relationship of fine-grained quartz and prevailing winds
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Relationship of fine-grained quartz and prevailing winds
Fig. 4.6b
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13. Neritic lithogenous sediments
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Neritic lithogenous sediments
Beach deposits
Mainly wave-deposited quartz-rich sands
Continental shelf deposits
Relict sediments
Turbidite deposits
Glacial deposits
High latitude continental shelf
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14. Pelagic lithogenous sediments
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Pelagic lithogenous sediments
Sources of fine material:
Volcanic ash (volcanic eruptions)
Wind-blown dust
Fine-grained material transported by deep ocean currents
Abyssal clay (red clay)
Oxidized iron
Abundant if other sediments absent
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15. Dr. C. Dong 03/16/10
Exe
1. How many types of marine sediments we have in terms of their orgin? 2. What features of marine sediments do we study? 3. Do we expect finer lithogenous sediments near Continental Margins or Deep-Ocean Basin?Why?
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16. Biogenous marine sediments (origin)
Dr. C. Dong 03/16/10
Hard remains of once-living organisms
Shells, bones, teeth
Macroscopic (large remains)
Microscopic (small remains)
Tiny shells or tests settle through water column
Biogenic ooze (30% or more tests)
Mainly algae and protozoans
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17. Biogenous marine sediments (composition)
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Biogenous marine sediments (composition)
Commonly either calcium carbonate (CaCO3) or silica (SiO2 or SiO2·nH2O)
Usually planktonic (free-floating)
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18. Silica in biogenic sediments
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Silica in biogenic sediments
Diatoms (algae)
Photosynthetic
Diatomaceous earth
Radiolarians (protozoans)
Use external food
Siliceous ooze
Fig. 4.7b
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19. Distribution of biogenous sediments
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Distribution of biogenous sediments
Most common as pelagic deposits
Factors controlling distribution
Productivity
Destruction (dissolution)
Dilution
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20. Carbonate deposits Stromatolites
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Carbonate deposits
Limestone (lithified carbonate sediments)
Stromatolites
Warm, shallow- ocean, high salinity
Cyanobacteria
Fig. 4.10a
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21. Dr. C. Dong 03/16/10
Exe 09-02
1. What is the origin of biogeonous sediments? 2. Where can majority of biogeonous sediments found? 3. What are major chemical compositions of biogeoneous sediments?
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22. Dr. C. Dong 03/16/10
Hydrogenous marine sediments: derived from the dissolved material in water
Minerals precipitate directly from seawater
Manganese nodules
Phosphates
Carbonates
Metal sulfides
Small proportion of marine sediments
Distributed in diverse environments
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23. Iron-manganese nodules
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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
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24. Cosmogenous marine sediments
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Cosmogenous marine sediments
Macroscopic meteor debris
Microscopic iron-nickel and silicate spherules
Tektites
Space dust
Overall, insignificant proportion of marine sediments
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25. Mixtures of marine sediments
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Mixtures of marine sediments
Usually mixture of different sediment types
For example, biogenic oozes can contain up to 70% non-biogenic components
Typically one sediment type dominates in different areas of the sea floor
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26. Marine sediments often represent ocean surface conditions
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Temperature
Nutrient supply
Abundance of marine life
Atmospheric winds
Ocean current patterns
Volcanic eruptions
Major extinction events
Changes in climate
Movement of tectonic plates
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27. Exe. 09-03 What is the origin of hydrogenous sediments?
Dr. C. Dong 03/16/10
Exe
What is the origin of hydrogenous sediments?
What is the origin of cosmogenous sediments?
List at least five ocean surface condition can be represented by
marine sediments
Dr. C. Dong