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Sedimentary Rocks

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Sedimentary Rocks

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    1. Sedimentary Rocks Chapter 6

    2. What Are Sediments? Loose particulate material In order of decreasing size

    3. Sources of Sediments 1. From weathering & erosion 2. From chemical precipitation

    4. What Happens to Sediments 1. transported by: Water. Ice. Wind. Gravity. Most sediment is buried and converted to sedimentary rock.

    5. 2. Deposited by Rivers Wind Glaciers Other water When the transportation vector has run out of energy, the sediments are deposited (dropped). What Happens to Sediments

    6. River Sorting- Transporting & Depositing

    7. Principle of Original Horizontality

    8. Lithification Sediment becomes sedimentary rock through lithification, which involves: Compaction Cementation Recrystallization (of carbonate sediment) Ex: sand

    9. 3 Classes of Sedimentary Rock

    10. Clastic Sedimentary Rock From the weathering of other rocks – broken texture Clasts (larger pieces, such as sand or gravel) Matrix (mud or fine-grained sediment surrounding the clasts) Cement (the glue that holds it all together), such as: calcite iron oxide silica

    11. Gravel Clastic Rocks If rounded clasts = conglomerate If angular clasts = breccia

    12. Sand Clastic Rocks Different Sandstones based on dominate grains quartz grains = quartz sandstone feldspar grains = arkose sand-sized rock fragment grains = graywacke

    13. Silt Clastic Rocks Siltstone - Grain size 1/256 to 1/16 mm (gritty)

    14. Clay Clastic Rocks Grains less than 1/256 mm (smooth) Shale (if fissile – splits) Kaolinite (if massive) also called Claystone Note: Mud is technically a mixture of silt and clay. (Mudstone)

    15. Chemical Sedimentary Rocks Chemicals removed from seawater and made into rocks by chemical processes, or with help of biological processes (such as shell growth). 3 types Evaporites Carbonates Siliceous

    16. Chemical Evaporites From the evaporation of water (usually seawater). Rock salt - composed of halite (NaCl). Rock gypsum - composed of gypsum (CaSO4.2H20) Travertine - composed of calcium carbonate (CaCO3), and therefore, also technically a carbonate rock

    17. Chemical Carbonates Formed through both chemical & biochemical processes. Include the limestones (many types) Two minerals are dominant: Calcite (CaCO3) Dolomite (CaMg(CO3)2)

    18. Chemical Siliceous Dominated by silica (SiO2). From diatoms, radiolarians, or sponges. Diatomite - looks like chalk, but doesn’t fizz in acid. Made of diatoms. Also referred to as Diatomaceous Earth. Chert - Massive and hard, microcrystalline quartz. May be dark or light in color. Often replaces limestone. Does not fizz in acid.

    19. Biogenic (Organic) Sedimentary Rocks Coals organic matter (plants). Increasing depth of burial (temperature and pressure): Peat (porous, brownish plant fragments) Lignite (crumbly and black) Bituminous (dull to shiny and black; sooty; layers may be visible) Anthracite (extremely shiny and black; low density; not sooty

    20. Formations from Sediments Large enough to be recognized. Ex.- haystack rock, sand dunes, delicate arch, balanced rock

    21. Sedimentary Environments (Sinks) Places where sediments accumulate and sedimentary rocks form 3 Major Groups Continental Marine Transitional

    22. Terrestrial Environments Aluvial Fan Braided stream Lakes Rivers Levees Swamps Deserts Glacial

    23. Marine Environments Seas & oceans Continental shelf Continental slope and rise (deep sea fans) Abyssal plain Reefs

    24. Transitional Environments between the land and the sea.

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