Geol225 (test2)

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lbb2631
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9244
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Geol225 (test2)
Updated:
2010-03-05 15:13:32
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Sedimentary Rocks
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  1. What happens during sediment transport?
    Grain shape changes:rounding
  2. What is the most obvious feature of sedimentary rocks?
    layering or stratification is the most obvious feature
  3. What can sediment be transported by?
    Water, wind, and ice
  4. How much of detrital sediment is deposited into the world's oceans annualy?
    10 billion tons
  5. When sediment is transported the grains become what?
    Rounded
  6. How are the grains at the transport site?
    Angular
  7. What is sorting?
    Grains separated by size, shape,or density
  8. When transported by wind how are the sediment grains sorted?
    The grains are well sorted sand- least viscous means thinner
  9. When transported by water how are grains sorted?
    transports gravel- intermediate viscosity
  10. When transported by ice how are the grains sorted?
    Typically poorly sorted- high viscosity means thicker
  11. Grain size is also related to ENERGY. More energy=
    Bigger grains
  12. More viscosity of an agent means
    less sorting
  13. What can you tell about sediment transportation from
    grain shape?
  14. Shape = distance
  15. What can you tell about sediment transportation from
    grain sorting?
    Sorting = agent doing the transporting
  16. What can you tell about sediment transportation from
    grain size?
    Size = energy
  17. Agents of sediment transportation
    • Water, wind, ice
    • ! ! ALL are driven by GRAVITY
  18. Where do sediments end up?
    Depositional environments
  19. How do sediments become rocks (lithification)?
    • Compaction
    • Cementation
    • Recrystallization
  20. What is compaction?
    Reduces the volume of sediment
  21. What is Cementation?
    Precipitation of cement
  22. What is recyrstalization?
    • growth of minerals under higher temperature and pressure
    • *no new minerals are formed*
  23. What are the sediment types?
    • Clastic sediment
    • Chemical sediment
    • Biochemical sediment
  24. What is clastic sediment?
    -made of chunks of other rocks

    • Name based on grain size (clay, silt, sand, pebble)
    • Pebbles: Conglomerates, breccias
    • Sand: Sandstone
    • Silt: Siltstone
    • Clay: Claystone, Mudstone, or shale if fissile
  25. What is chemical sediment?
    rocks come from precipitation of dissolved minerals
  26. What is biochemical sediments?
    -plant and animal shells or skeletons

    • Limestone: either, comes from precipitated calcite,
    • maybe in form of shells or shell fragments
    • Chert: either biogenic or non-biogenic precipitated quartz
    • Coal: biogenic, from compaction of plant material
  27. Rocks created by organisms are
    Biogenic
  28. What is bioclastic?
    Rocks that are composed of shells or shell pieces
  29. Sedimentary structures reveal the history of the Earth's surface by what things
    • 1.Bedding
    • 2.Graded bedding (turbidites)
    • 3.Cross-bedding
    • 4.Ripple marks
    • 5.Mudcracks
    • 6.Fossils (Paleontology)
  30. What is bedding or stratification?
    • -the single most characteristic feature of sediments
    • -can originate in a river, floodplain, or in any basin
  31. What is graded bedding?
    forms when moving water suddenly slows down, dropping its sediment load (more energy=bigger grains)
  32. What are turbidites?
    piles of sediment that accumulate on the continental shelf- triggered by earthquakes
  33. What is cross-bedding?
    • forms when currents are present (wind or water)
    • -windward slide=shallow side
    • -leeward slide=steep side
    • *wind changes direction
    • *water has constant direction
  34. What are ripple marks?
    • small ridges with intervening troughs, giving them somewhat of a corrugated appearance.
    • Some ripple marks are symmetric and some are asymmetric
  35. What are mudcracks?
    clay-rich sediment that dries and shrinks and develops intersecting fractures called mudcracks
  36. What is sediment?
    Products of physical and chemical weathering
  37. What does the condition of the sediment tell you?
    Tells you something about where it came from and how it got there
  38. What is a sedimentary rock?
    formed when sediment is lithified

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