1 / 20

Ocean Sediments

Ocean Sediments. Origin and Distribution. Continental Margins and Ocean Basins. Review from last week. Shape of ocean floor. Continental Margins Active Margins Passive Margins. Ocean Basins. Marine Sediments. Most ocean floor covered by marine sediments.

aricin
Download Presentation

Ocean Sediments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Ocean Sediments Origin and Distribution

  2. Continental Margins and Ocean Basins • Review from last week • Shape of ocean floor • Continental Margins • Active Margins • Passive Margins • Ocean Basins

  3. Marine Sediments • Most ocean floor covered by marine sediments • Sediment thickness is thinnest at mid-ocean ridge and thickest at continental margins

  4. Types of Ocean Sediments • Terrigenous – “rock-derived” • Biogenous – “life-derived” • Hydrogenous – “water-derived” • Cosmogenous – “cosmic-derived”

  5. LithogenousSediments • Composed mostly of quartz sand and clay • Derived from the weathering of rocks • – continents or volcanic islands • Transported by rivers, glaciers or wind • Most deposited on continental margins • Covers about 45% of ocean floor

  6. Sediment Distribution - Terrigenous

  7. Terigenous Sediment - Examples Mississippi River Sahara Desert Mt. Pinatubo • Red Clays • Sediment from rivers, dust, and volcanic ash • Transported to deep ocean by winds and surface currents • Common in deep oceans • Accumulates 2 mm (1/8”) every 1,000 years

  8. Biogenous Sediment • Biogenic ooze – greater than 30% biogenous sediment • Composed mostly of hard skeletal parts of once-living organisms • Two main compositions of hard parts: • Calcium Carbonate (CaCO3) • Coccolithophore (phytoplankton) • Foraminifera (zooplankton) 2. Silica (SiO2) a) Diatoms (phytoplankton) b) Radiolarian (zooplankton)

  9. Sediment Distribution - Biogenous • Calcareous and Siliceous Oozes

  10. Biogenous – Calcareous Examples • Composed of CaCO3 Foraminifera Foraminifera • Widespread in relatively shallow areas Coccolithophore

  11. Biogenous – Calcareous oozes • Cold bottom waters undersaturated with respect to CaCO3 • slightly acidic ( CO2) • readily dissolves CaCO3 • Cover greater than 50% of ocean floor • Distribution controlled by dissolution processes • Calcium Carbonate Compensation Depth (CCD) – the depth at which the rate of accumulation of calcareous sediments equals the rate of dissolution • Pacific Ocean – 500-1,500 m CaCO3 is found • Atlantic Ocean – 4,000 m

  12. Sediment Distribution – Calcareous/Siliceous

  13. Biogenous – Siliceous Ooze Examples Radiolarians • Composed of SiO2 • Base of food chain Diatoms

  14. Biogenous – Siliceous Ooze • Covers 15% of ocean floor • Distribution - areas of high productivity (zones of upwelling) • Dissolve more slowly than calcareous particles • Diatoms common at higher latitudes • Radiolarians common at equatorial regions

  15. Siliceous Oozes

  16. Sediment Distribution - Hydrogenous

  17. Hydrogenous Sediments • Produced by chemical processes in seawater • Sediment precipitates from water • Some Examples: • Oolites – occur in surface waters supersaturated in CaCO3 • Manganese Nodules – manganese, iron deposits accumulate in areas of low sedimentation • Evaporites – “salt precipitates” form in areas of high evaporation

  18. Hydrogenous - Examples Sea salt Manganese Nodules Oolitic sand

  19. Cosmogenous – microtektites Tektites – result from collisions with micrometeors Fragments of Earth’s crust melt and spray outward from impact crater Crustal material re-melts as it falls back and forms glassy tektites Microtektites • Sediments derived from extraterrestrial material (micrometeorites) • Widespread but not abundant

  20. Sediment Distribution

More Related