sedimentary

• Types of weathering


  • Mechanical
  • Chemical
  • Biological
• Chemical weathering


  • Carbonation
  • Hydrolysis
  • Solution
  • Oxidation
• Mechanical weathering - Freeze-thaw

  1. Water enters joints

  2. Freezes at night

  3. Thaws during day, weakening rock structure

  4. Eventually causes rock to break apart
• Mechanical weathering - Insolation


  1. Expansion and contraction of minerals in rock due to solar radiation

  2. Exerts pressure on outer mineral layers, causing them to peel off
• Mechanical weathering - Pressure release

  1. Movement of rock towards surface through erosion of overlying rock

  2. Releases pressure, causing fracturing
• Biological weathering


  • Root action
  • Burrowing
• Types of erosion


  • Abrasion
  • Attrition
  • Corrosion
  • Hydraulic action
  • Flocculation
• Grain size


  • Clays & silts <1/16mm
  • Sands 1/16mm-2mm (fine, medium and coarse)
  • Gravels >2mm
• Flow velocity of a river

  Determines grain size that can be transported and eroded
• Sedimentary rocks from grains

  • Gravels->Breccia/Conglomerate
  • Sands->Arkose/Greywacke/Aeolian/Orthoquartzite
  • Clays & silts->Shale/Mudstone
• Sedimentary structures


  • Imbricate structure
  • Ripple marks
  • Rip up clasts
  • Cross bedding
  • Graded bedding
  • Load casts
  • Flame structures
  • Desiccation cracks
• Carbonates and limestones


  • Composition >50% calcium carbonate or dolomite
  • Formed from precipitation or organic remains
  • Can be chemically or biologically formed
• Limestone types


  • Oolitic
  • Fossiliferous
  • Chalk
• Rocks can be classified as compositionally mature or texturally mature