Study Guide available! Web site (dusk2.geo.orst.edu/oceans) Go to the syllabus page and click on the Study Guide for Tes

1. Study Guide available!Web site (dusk2.geo.orst.edu/oceans)Go to the syllabus page and click on the Study Guide for Test#1

2. Lecture 9: Marine Sediments What’s all that muck at the bottom of the ocean, and what’s it good for?

3. Marine Sediments are: • Particles of various sizes derived from a variety of sources that are deposited on the ocean floor • A vast “library” recording geologic, oceanographic and climatic conditions • Remarkably complete compared to land

4. Where do these come from? • Inputs are:-- rivers-- atmosphere-- surface waters-- volcanoes (both on land and submarine) -- deep ocean water-- outer space

5. Classifications • By SizeClay -- Silt -- Sand -- Pebble -- Cobble 0.001 mm 1 mm 100 mm • Effects of water velocity on transport: rivers and near-shore vs open ocean

6. Sediment Transport • Fluid velocitydetermines thesize of theparticles thatcan be moved

7. Size Sorting

8. Classifications • By OriginBiogenousTerrigenousHydrogenousCosmogenous

9. Terrigenous sediments (from land) • Rivers • Winds (eolian) • Glaciers (ice-rafted debris, IRD) • Turbidites • Sea level changes

10. River sediment loads (106 tons/yr)

11. Glacial (Ice-rafted debris)

12. Turbidites • Rapidly-accumulated terrestrial sediments • Earthquake-triggered submarine avalanches • High velocity (~50 mph!), erosive events • Good examples preserved on Mary’s Peak

13. Turbidites (avalanches)

14. Sea Level Changes

15. Biogenous sediments (from living things) • Calcareous (CaCO3)Foraminifera -- animalsCoccolithophores -- plants • Siliceous (SiO2)Radiolaria -- animalsDiatoms -- plants

16. mm = micron = millionth of a meter!

17. mm = micron = millionth of a meter!

18. mm = micron = millionth of a meter!

19. mm = micron = millionth of a meter!

20. Productivity = skeletons and soft tissue • Accumulation depends on production and preservation • SiO2 is preserved everywhere • CaCO3 is variable, depending on P, T, pH

21. Carbonate Compensation Depth South North

22. Carbonate Compensation Depth • The depth at which carbonate input from the surface waters is balanced by dissolution in corrosive deep waters • In today’s ocean this depth (CCD) varies between 3 km (polar) and 5 km (tropical) • Thus, accumulation rates vary a lot!

23. Accumulation Rates for Oozes • Productivity • reproduction of planktonic organisms • Preservation • silica dissolves only very slowly • calcium carbonate varies with depth • Ratesare variable: <1 to 15mm/1000 yr

24. Coastal waters are often highly productive, with abundant planktonic organisms thriving in the surface waters. Why then are biogenous oozes rarely found nearshore?? • Do biogenous sediments dissolve readily at shallow depths on the continental shelf? NO • Do plankton species in coastal waters lack skeletons? NO • Are planktonic organisms consumed by large organisms, preventing deposition of skeletons? NO

25. the large input of terrigenous sediment to the continental margin overwhelms the biogenous component in the sediment. YES

26. Hydrogenous (from sea water) • Metalliferous sediments at spreading ridges • Manganese nodules • Evaporites -- Salt deposits

27. baseball to bowling ball size!

28. Cosmogenous (from outer space) • Meteorites and comets

29. Sediment Accumulation

30. Sediment succession

31. Distribution of Marine Sediments