Sedimentary Processes and Its Products

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Sedimentary Processes and Its Products
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Weathering

• Definition The disintegration and decomposition
  of rock at or near the earths surface
• Two types
• a. Mechanical
• b. Chemical

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Weathering

• Mechanical weathering - Physical disintegration
  of rock resulting in smaller fragments
• Chemical weathering Decomposition of rock
  involving a chemical transformation into one or
  more new compounds

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Agents of Mechanical weathering

• Frost wedging
• Unloading
• Thermal expansion
• Organic activity

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Alternate freezing And thawing
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Unloading

• Exfoliation texture exhibited by rocks that
  have peeled-off in sheets during weathering.

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Thermal expansion

• Expansion and contraction from the daily cycle of
  temperature change (day and night)

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Organic activity

• Breakdown due to the growth of organic materials

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Types of chemical weathering

• Solution
• Oxidation
• Hydrolysis

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Solution

• Change of matter into liquid state by combination
  with a liquid

• CaCO3 2H (H2O) ?
• calcite aqueous acid
• Ca CO2 3H2O
• calcium carbon water
• ion dioxide

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Oxidation

• O2 combines with Iron to form rust

• 4 Fe 3O2 ? 2Fe2O3
• iron oxygen iron
• oxide

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Hydrolysis

• Alteration of mineral through a chemical reaction
  with acidic water

2KAlSi3O8 2(H HCO3) H2O ? orthoclase
carbonic acid Al2Si2O5(OH)4 2K 2HCO3
4SiO2 kaolinite clay potassium bicarbonate
ion silica
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sediments
erosion
transport
deposition lithification
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Sedimentary rocks

• Definition rock formed from weathered products
  of pre-existing rocks that have been transported,
  deposited and lithified.
• 5 by volume of earths crust (outer 16 km)
• 75 of all exposed rocks

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Sedimentary rocks

• Indicators of past environments
• Group of rocks used largely to reconstruct
  earths history
• Economic importance is immense!
• Source of petroleum (oil and gas)

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Types of sedimentary rocks

• Clastic classification based on size of
  particles (sediment)
• Non-clastic classification based on chemical
  composition

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Clastic rocks

• Sorting During transport of sediments, large
  sized clasts are sorted from the smaller ones

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Energy of transporting medium
High Low
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Non-clastic sedimentary rock

• Limestone (CaCO3)
• Chert (SiO2)
• Flint (black)
• Jasper (Red)
• Agate (Banded)
• Evaporites
• Coal

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Depositional environment
The place where sedimentary rocks are
formed Indicators of the environment of
deposition are sediment size, composition and
STRUCTURES.
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Depositional environment
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Depositional environment