More on Sedimentary Rocks

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More on Sedimentary Rocks
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Back to classification of sed. rocks
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A sedimentary overview

• Clastic (or detrital) sedimentary rocks are made
  up of particles of pre-existing rocks or minerals
• Chemical sedimentary rocks are made up of
  chemical precipitation of minerals and are
  cystalline, and often composed of only one
  mineral
• Biochemical (organic) sedimentary rocks are
  primarily made up of biological detritus, like
  skeletal or shell or leaf material. A rock is
  organic if 50 or more is made of organic
  material.
• Many sedimentary rocks contain a combination of
  the three components, and are classified on the
  dominant type present.

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Depositional Environments
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Quiet Depositional Environments

• Lagoons, shallow seas, streams, creeks, really
  deep sea
• Types of rocks you would find here
• Coal, evaporites (gypsum, salts, etc.),
  limestones, shales, mudstones, siltstones

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High Energy Depositional Environments

• Alluvial fans, landslides, beaches, mountains
• What kind of rocks would you expect?
• Breccias, conglomerates, sandstones

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Alluvial Fans

• Typically associated with flash flooding or
  mass-wasting (landslides)
• Found in mountainous areas especially deserts
  since they are so prone to flash-flooding

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