Sea Floor Sediments

1. Sea Floor Sediments

2. 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

3. Turbidity Currents – move sediments long distances

4. Submarine Canyons – Formed by Turbidity Currents

6. 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

7. Sediments: Classification • By size • By mineralogy • By source

8. Sediment Size Classification

9. Sediment Thickness in the Oceans

10. Distribution of Marine Sediments

11. Sediment Classification by Source • Terrigenous • Biogenous • Hydrogenous • Cosmogenous

15. 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

16. 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

17. 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

18. 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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20. Foraminifera

21. Coccolithophores

22. Radiolarians

23. Diatoms

24. 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

25. Seafloor Sediments • Hydrogenous sediment • Minerals that crystallize directly from seawater • Most common types include • Manganese nodules • Calcium carbonates • Metal sulfides • Evaporites

26. Cosmogenous Sediment • From space—dust and meteorite debris • Very small proportion of sediment • e.g. tektite spheres, glassy nodules

27. Distribution of Marine Sediments