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Sea Floor Sediments PowerPoint PPT Presentation


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Sea Floor Sediments. Seafloor Sediments. Ocean floor is mantled with sediment Sources Turbidity currents Sediment that slowly settles to the bottom from above Thickness varies Thickest in trenches —A ccumulations may approach 10 kilometers .

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Sea Floor Sediments

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Sea Floor

Sediments


Seafloor Sediments

  • Ocean floor is mantled with sediment

  • Sources

    • Turbidity currents

    • Sediment that slowly settles to the bottom from above

  • Thickness varies

    • Thickest in trenches—Accumulations may approach 10 kilometers


Turbidity Currents – move sediments long distances


Submarine Canyons – Formed by Turbidity Currents


Seafloor Sediments

  • Thickness varies

    • Pacific Ocean—About 600 meters or less

    • Atlantic Ocean—From 500 to 1000 meters thick

  • Mud is the most common sediment on the deep-ocean floor


Sediments: Classification

  • By size

  • By mineralogy

  • By source


Sediment Size Classification


Sediment Thickness in the Oceans


Distribution of Marine Sediments


Sediment Classification by Source

  • Terrigenous

  • Biogenous

  • Hydrogenous

  • Cosmogenous


Terrigenous Sediment

  • From erosion of land, volcanic eruptions, blown dust from wind storms, glaciers and icebergs

  • Dominant around continental margins and in polar oceans

  • Cover ~45% of ocean floor, although they have the greatest volume of all types

  • e.g. quartz sands, clays


Seafloor Sediments

  • Terrigenous sediment

    • Material weathered from continental rocks

    • Virtually every part of the ocean receives sediment from land

    • Fine particles remain suspended for a long time and are carried by currents


Biogenous Sediment

  • Hard parts of some marine organisms – living organisms

  • Covers ~55% of ocean floor and is dominant in deep ocean

  • e.g. calcareous oozes from foraminifera, pteropods, and coccolithophores; siliceous oozes from radiolarians and diatoms; phosphatic components from fish bones and teeth


Seafloor Sediments

  • Biogenous sediment

    • Shells and skeletons of marine animals and plants

    • Most common are calcareous oozes produced from microscopic organisms

    • Siliceous oozes composed of skeletons of diatoms and radiolarians

    • Phosphate rich materials derived from the bones, teeth, and scales of fish and other marine organisms


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Foraminifera


Coccolithophores


Radiolarians


Diatoms


Hydrogenous Sediment

  • From precipitation of dissolved material in seawater by bacteria or through evaporation

  • Covers <1% of the ocean floor and is normally found only with other sediments

  • e.g. manganese nodules


Seafloor Sediments

  • Hydrogenous sediment

    • Minerals that crystallize directly from seawater

    • Most common types include

      • Manganese nodules

      • Calcium carbonates

      • Metal sulfides

      • Evaporites


Cosmogenous Sediment

  • From space—dust and meteorite debris

  • Very small proportion of sediment

  • e.g. tektite spheres, glassy nodules


Distribution of Marine Sediments


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