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Marine Sediments: Origins, Features, and Distribution

Explore the classification, origins, textures, and compositions of marine sediments. Learn about the distribution of neritic and pelagic sediments, as well as biogenous, hydrogenous, and cosmogenous sediments.

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Marine Sediments: Origins, Features, and Distribution

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  1. CHAPTER 4: Marine Sedimentsat ECC

  2. Marine sediments • Eroded rock particles and fragments • Transported to ocean • Deposit by settling through water column • Oceanographers decipher Earth history through studying sediments

  3. 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)

  4. Features of marines sediments • Origin • Distribution • Texture • Composition

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

  6. Distribution of neritic and pelagic marine sediments • Neritic sediments cover about ¼ of sea floor • Pelagic sediments cover about ¾

  7. Distribution of neritic and pelagic marine sediments Fig. 4.19

  8. Lithogenous Sediments Origin • 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)

  9. Lithogenous Sediments Texture Fig. 4.5

  10. Sediment texture • Grain size • Proportional to energy of transportation and deposition Table 4.2

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

  12. Relationship of fine-grained quartz and prevailing winds Fig. 4.6b

  13. Neritic lithogenous sediments • Beach deposits • Mainly wave-deposited quartz-rich sands • Continental shelf deposits • Relict sediments • Turbidite deposits • Glacial deposits • High latitude continental shelf

  14. 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

  15. Exe 09 - 01 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?

  16. Biogenous marine sediments (origin) • 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

  17. Biogenous marine sediments (composition) • Commonly either calcium carbonate (CaCO3)orsilica(SiO2 or SiO2·nH2O) • Usually planktonic (free-floating)

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

  19. Distribution of biogenous sediments • Most common as pelagic deposits • Factors controlling distribution • Productivity • Destruction (dissolution) • Dilution

  20. Carbonate deposits Limestone (lithified carbonate sediments) • Stromatolites • Warm, shallow-ocean, high salinity • Cyanobacteria Fig. 4.10a

  21. 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?

  22. 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

  23. 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

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

  25. 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

  26. Marine sediments often represent ocean surface conditions • Temperature • Nutrient supply • Abundance of marine life • Atmospheric winds • Ocean current patterns • Volcanic eruptions • Major extinction events • Changes in climate • Movement of tectonic plates

  27. Exe. 09-03 • 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

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