SEDIMENTS

1. SEDIMENTS

2. SEDIMENT DEPOSITS • insoluble residues of weathering and biological processes • preserve a record of ocean basin history over time

3. Sources of sediment particlesTable 4.1 p 98 • Biogenous - from organisms contains > 30% by volume shells, bones, and teeth of marine organisms • Lithogenous - rock fragments or minerals from weathering of rocks on land and from volcanic eruptions • Hydrogenous - formed by chemical reactions • Cosmogenous - debris from meteorites

4. Sources of sediment particles cont. • sorting particles by size • poorly sorted - particles of wide ranging size • well sorted - sand on beaches (because waves have removed all the smaller particles) • deep-sea mud - very fine grained particles

5. Biogenous sediments • T 57, 58, 59 Holoplankton • Fig 4.7,and 4.8 pp 107, and 109 • controlling processes • 1. production - biological processes • 2. destruction - chemical processes • 3. dilution

6. Biogenous sediments cont. • production - siliceous SiO2 . n HOH (opal) sediments accumulate under highly productive waters (radiolarian) • 1. diatomaceous (plants) sediments dominate the subpolar North Pacific and around Antarctica • 2. radiolarian (animals) - rich sediments in the equatorial Pacific and Indian oceans • 3. Stromatolites - formed in shallow water by the trapping and binding of sedimentary grains by photosynthetic algae, thus laying down layer after layer of algal colonies.

7. Opal diatom radiolarian • Stromatolites

8. Biogenous sediments cont. • destruction • 1. siliceous shells and phosphate bones and teeth - dissolve everywhere in the ocean and are deposited only below highly productive regions such as upwelling areas - resistant particles such as fish teeth or whale ear-bones can persist for a long time and are often the nuclei of manganese nodules • 2. related to chemistry of carbonates in sea water • 3. dissolved it great depths

9. Lithogenous sediments • T 56 • from silicate rocks • produced primarily by weathering of rocks on land • transported to ocean by rivers, wind (most from deserts), and glaciers (act like rivers carrying along would be sediment)

10. Lithogenous sediments

11. Hydrogenous sediments • iron-manganese nodules most important (Fe2O3 and MnO2) Fig 4.15 p. 114book • iron and manganese come from hydrothermal vents and from land - whale ear-bones • nodules grow slowly by accumulating tiny particles on rocks or bones (whale ear bones) a • few nodules seen in the Atlantic because they are buried by sediment • slow sediment formation and disturbance by organisms in the Pacific keep manganese from being buried b

12. Minerals from the ocean a b

13. Origen of hydrogenous sediment • Precipitation of certain minerals due to chemical reactions occur with change in conditions such as temperature, pressure, or addition of other chemicals.

14. Hydrogenous Sediment

15. Cosmogenous sediments • debris from meteorites - ~ 30,000 metric tons / year fall into the ocean • distinctive chemical and mineral composition - iron or iron rich minerals • we know they come from outer space because of their morphology (melting)

16. Cosmogenous sediments

17. Sediment transport by water • T 56 • controlled by water speeds and by settling velocities of particles (determined by particle size) • sand deposited near source, e.g., beaches near rivers • clays more widely dispersed - small particles

18. particle diameter Settling velocity time to settle 4 km • sand 100 mm 2.5 cm/sec 1.8 days • silt 10 0.025 185 days • clay 2 0.00025 50 years • Table 4.2 p 105

19. Organisms filter sea water, removing and depositing unwanted particles fecal pellets Fig 421 p 121 • very important way to increase settling rate of fine particles • Plants filter and stabilize sediments in wetlands

20. Fecal pellet

21. Sediment transport by wind • Particles eroded from deserts and high mountains • Transported to center of ocean basins where little waterborne sediment reaches • Plumes of iron-stained sand blown into Atlantic from Sahara • Volcanic ash - the bigger the eruption the greater distance the ash will travel

22. Deep-sea sediments • Pelagic sediments - deposits covering much of the deep-ocean floor • Particles accumulate slowly, like a gentle snow fall • Fig 4.20 p. 120 book

23. Turbidity currents Box 3.3 • dense mixtures of water and sediment • near land, large masses of sediment transported in turbidity currents • triggered by earthquakes (can be very destructive breaking telegraph cables moving at speeds of to 11 Km / hr) or river floods • moves like avalanche - carries sediment to the ocean-bottom animal and plants alike • turbidity currents remove sediment from canyons, keeping them open • forms characteristic deposits - course grained at bottom, fine grained at top (called graded bed) • current movements blocked by submarine ridges and trenches

24. Continental margin deposits • continental margins are usually covered by thick deposits - from rivers - most from rivers in the Asian continent • continental shelf sediments deposits may have formed under conditions no longer prevailing - relict sediments Look again at Terranes againS&A 41 • may have been affected by exposure during lower sea levels - such as oyster shells found on U.S. continental shelf • marginal ocean basins - contain thick sediment deposits - contain about 1/6 of all oceanic sediments and are major sources of oil and gas

25. Distribution of neritic and pelagic seciment • Fig 4.19 p. 117 T 60, 61, & 62 • Pelagic sediment • Calcareous ooze • Foraminifera • pteropod • Siliceous ooze • Diatome • Radiolarian

26. Calcite Compensation Depth CCD T63 • Calcium carbonate (calcite) dissolves at an increasing rate with increasing depth until the CCD is reached. Calcium carbonate in sediment is not seen at greater depths because it is desolved.

27. Deciphering ocean history • Sediments record basin history • Ages determined from fossils, radioactive dating, or magnetic orientation of minerals (like dating sea floor) • Read Box 4.3 p 118

28. Oil and Gas • comes from decomposition of organic matter from plants • anoxia - very low or absent dissolved O2 • water column was highly stable • very dense bottom waters • organic matter was protected against decomposition by bacteria or utilization by benthic organisms

29. Oil and Gas cont. • Factors for formation of oil and gas deposits • sediment deposits rich in organic matter • heating to form oil and gas (100-150oC) • porous rocks (reservoir) to hold oil and gas • Zooplankton and algae gives petroleum, and land plants gives you coal

30. Minerals from the ocean • sand, gravel, shells produced in large quantities • river deposits of heavy minerals - tin, gold, diamonds • phosphorites nodules - formed from decomposition of bones • manganese nodules - not yet produced commercially

31. Minerals from the ocean • Phosphorites Magnesium ear bones

32. END good luck on all your exams