Sedimentary

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Chapter 6
Sedimentary rocks
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Chapter 6
Sedimentary rocks

• Origin/introduction
• Detrital sedimentary rocks
• Chemical sedimentary rocks

• byproducts of rock weathering
• become sediments, cement together

• mechanical/chemical rock weathering byproducts
• are transported to new location, cement together

• soluble material, dissolved by chemical
  weathering,
• precipitates by organic or inorganic processes

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Chapter 6
Sedimentary rocks

• Origin/introduction

- weathering, erosion, transport, deposition is
continuous - sedimentary rocks always being made
found nearly everywhere - 75 of all rock
outcrops on continents - contain evidence of
past events and environments - quite important
economically
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Chapter 6
Sedimentary rocks

• Detrital (or clastic)
• sedimentary rocks

• pieces (clasts) of pre-existing rock

• Mostly clay minerals (weathering of feldspar)
• quartz (resistant to weathering)

• Presence of minerals (like feldspars) indicates
• -little weathering
• -short transport

• particle (clast) size
• primary distinguishing factor

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Chapter 6
Sedimentary rocks

• Detrital (or clastic)
• sedimentary rocks

• Size of clasts (particles)

common name
size
Detrital rock

• gravel bigger than 2 mm
  conglomerate
• (1/10 inch)
  or breccia

• sand sand-sized
  sandstone

• silt, mud, clay very fine-grained
  shale or mudstone

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sediments
sedimentary rocks
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Chapter 6
Sedimentary rocks

• Detrital sedimentary rocks

• Shale siltstone

• silt clay-sized particles (mud, clay, silt)

• over 1/2 of all sedimentary rocks

• particles too small to identify w/ eye

• forms slopes at surface

• raw material for brick, tile, pottery, china

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Chapter 6
Sedimentary rocks

• Detrital sedimentary rocks

• Sandstone

• composed of sand grains

• 2nd most abundant sedimentary rock

• deposited by moderate currents
• - rivers deltas
• - beaches
• - wind (sand dunes)

• mostly quartz (strong chemically stable)

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Chapter 6
Sedimentary rocks

• Detrital sedimentary rocks

• Sandstone

• sorting

degree of similarity in particle size
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Chapter 6
Sedimentary rocks

• Detrital sedimentary rocks

• Sandstone

• shape

degree of roundedness
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Shapes of sand grains
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- well-sorted - well-rounded
The quartz sand above is
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Another example
Well-sorted
Poorly-sorted
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Chapter 6
Sedimentary rocks

• Detrital sedimentary rocks

• Conglomerate

• composed mostly of gravel
• pebbles to boulders

• poorly sorted

• deposited by strong, turbulent currents
• - big flooding rivers
• - steep streams (near mountains)
• - glaciers

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Chapter 6
Sedimentary rocks

• Detrital sedimentary rocks

• Breccia

• conglomerate with angular grains

• didnt travel far

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Chapter 6
Sedimentary rocks

• Chemical
• sedimentary rocks

• derived from material carried in solution to
  lakes/seas

• precipitation from solution to form chemical
  sediments

• 2 types of precipitation
• - inorganic
• - organic

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Chapter 6
Sedimentary rocks

• Chemical sedimentary rocks

• Limestone

• 10 of all sedimentary rocks (by volume)

• most abundant chemical sedimentary rock

• composed primarily of calcite (calcium carbonate
  CaCO3)

• formed by marine organisms (corals, clams, algae)

• some deposited directly out of ocean or other
  waters

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Chapter 6
Sedimentary rocks

• Chemical sedimentary rocks

Organic rock of biochemical origin

• coquina (rock of shell fragments)

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Coral reef
limestone mountain
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Chapter 6
Sedimentary rocks

• Chemical sedimentary rocks

• Chert

• very fine grained silica

• also called flint, jasper, agate

• most formed in ocean

• occurs as layers (beds) as irregular blobs in
  limestone

• marine creatures remove silica from sea water,
  make shells

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Chapter 6
Sedimentary rocks

• Chemical sedimentary rocks

• Evaporites

• water evaporates and dissolved stuff is deposited

• mostly marine rocks, but some lakes/ playas

• Salt, gypsum, potash

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Chapter 6
Sedimentary rocks

• Chemical sedimentary rocks

• Coal

• buried and compacted plant material

• different kinds of coal, depending on formation
  process