UNIVERSITY OF SOUTH AUSTRALIA

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UNIVERSITY OF SOUTH AUSTRALIA

• INTRODUCTORY AND ENVIRONMENTAL GEOLOGY
• Week 7 Workshop
• Surficial Deposits

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Surficial Deposits

• Surface deposits can contain
• Transported material
• Residual material
• Material can be transported by
• Water
• Wind
• Gravity

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Transported Materials

• Water can transport
• gravel
• sand
• silt
• clay
• Wind can transport
• sand
• silt
• clay
• Gravity can transport
• gravel
• sand
• silt
• clay

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Residual Deposits

• Can be result of
• Mechanical weathering
• Chemical weathering
• Combination of mechanical and chemical weathering
• Mechanical weathering ? reduction in grain size
• Chemical weathering ? new minerals commonly
  clays

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Soil Profile

• Chemical weathering produces soil profile that
  shows gradation from fresh rock through weathered
  rock to soil.

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Soil Profile

• The nature of the soil profile depends on
• underlying rock type
• climate
• slope
• time

Hamblin (1992) Earths Dynamic Systems
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Soil Profile

• Soil profile on granite and schist

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Calcrete

• In semi-arid to arid climates, solution and
  redeposition of calcite can lead to the
  development of calcrete
• Calcrete can occur as
• carbonate nodules in soil
• carbonate cemented sheets

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Laterite

• In tropical conditions, extreme chemical
  weathering can produce laterite or ferricrete
• Leaching transports
• iron towards the surface where it is deposited as
  iron oxides/hydroxides
• silica and aluminium downwards
• Laterite can occur as
• loose nodules
• cemented hard layer

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Laterite Profile
http//mindepos.bg.tu-berlin.de/eurolat/lateri/lat
erit5.gif
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Silcrete

• In arid climates, silica can be dissolved and
  reprecipitated at the surface to form a hard
  silica capping called silcrete

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Unified Soil Classification