Class Test - Sedimentary

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Anonymous
ID:
86532
Filename:
Class Test - Sedimentary
Updated:
2011-05-18 06:07:29
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geology
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Description:
Sedimentary Rock Characteristics
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  1. Formation of clastic sedimentary rocks
    • Weathering
    • Erosion
    • Transportation
    • Deposition
    • Lithification (loose sediment transformed into solid rock)
  2. Process of lithification
    Burial of sediment by more sediment

    Overburden squeezes out air and water

    Clasts press tightly together = compaction

    Minerals (commonly quartz or calcite) form cement between clasts = cementation
  3. Clast size
    Length of diameter of clasts making up the rock

    Boulder, cobble, pebble, sand, silt, clay
  4. Clast composition
    Makeup of clasts within rock

    Larger clasts (pebbles or larger) consist of rock fragments = aggregate of many mineral grains

    Smaller clasts (sand or smaller) consist of individual mineral grains
  5. Angularity and sphericity
    Angularity = smooth or angular corners and edges of clasts

    Sphericity = degree to which clast is equidimensional (i.e. resembles a sphere)
  6. Sorting
    Degree to which clasts are the same size
  7. Well-sorted
    Sediment all the same size
  8. Poorly-sorted
    More than one grain size
  9. Character of cement
    In some rocks, the cement consists of silica (quartz), in others of calcite
  10. Coarse to very coarse
    Rounded pebbles and cobbles =
    Conglomerate
  11. Coarse to very coarse
    Angular clasts =
    Breccia
  12. Coarse to very coarse
    Large clasts in muddy matrix =
    Diamictite
  13. Medium to coarse
    Sand-sized grains =
    Sandstone
  14. Medium to coarse
    Sand-sized grains
    Quartz grains only =
    Quartz sandstone
  15. Medium to coarse
    Sand-sized grains
    Quartz and feldspar sand =
    Arkose
  16. Medium to coarse
    Sand-sized grains
    Sand-sized lithic clasts =
    Lithic sandstone
  17. Medium to coarse
    Sand-sized grains
    Sand and lithic clasts in a clay-rich matrix
    Wacke
  18. Fine
    Silt-sized clasts
    Siltstone
  19. Very fine
    Clay and/or very fine silt
    • Shale (platy sheets)
    • Mudstone (no platy sheets)

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