Sedimentary

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Sedimentary MetamorphicRocks

• Formation of Sedimentary Rx
• Types of Sedimentary Rx
• Metamorphic Rx

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Thought Question

• What are some features/objects you might find in
  a sedimentary rock that you wouldnt find in an
  igneous rock?
• Name and describe one natural process that
  demonstrate weathering and/or erosion.
• Explain where you would expect to find rocks that
  have been metamorphosed.

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Objectives

• Identify the correct sequence of the formation of
  sedimentary rocks
• Name the three main types of sedimentary rocks
  and describe several identifiable sedimentary
  rock features
• Describe clastic sedimentary rocks
• Explain how chemical sedimentary rocks form
• Describe organic sedimentary rocks
• Compare and contrast the different types and
  causes of metamorphic rocks
• Distinguish between regional and contact
  metamorphism
• Explain the difference between metamorphic rock
  features
• Identify foliated and non foliated rocks and give
  examples of each

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Formation of Sediment

• Sediments are pieces of solid material that have
  been deposited on Earths surface by wind, water,
  ice, gravity, or chemical precipitation.
• When sediments become cemented together, they
  form sedimentary rocks.
• The formation of sedimentary rocks begins when
  weathering and erosion produce sediments.
• Chemical dissolving rocks
• Physical breaking into smaller pieces

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Erosion

• Erosion is the removal and movement of surface
  materials from one location to another.
• The four main agents of erosion are wind, moving
  water, gravity, and glaciers.
• Deposition occurs when sediments are laid down on
  the ground or sink to the bottoms of bodies of
  water.
• Sediments are deposited when transport stops.
• As water or wind slows down, the largest
  particles settle out first, then the
  next-largest, and so on, so that different-sized
  particles are sorted into layers.

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Burial

• Most sediments are ultimately deposited on Earth
  in depressions called sedimentary basins where
  they are layered and buried.
• Lithification includes the physical and chemical
  processes that transform sediments into
  sedimentary rocks.
• As more and more sediment is deposited in an
  area, the bottom layers are subjected to
  increasing pressure and temperature which causes
  lithification.

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Lithification

• There are two common types of cementation.

• A new mineral, such as calcite (CaCO3) or iron
  oxide (Fe2O3) grows between sediment grains as
  dissolved minerals precipitate out of groundwater.

• Existing mineral grains grow larger as more of
  the same mineral precipitates from groundwater
  and crystallizes around them.

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Sedimentary Rx- Three Classes

• Clastic- Sedimentary rx made up of rock
  fragments carried by water, wind or ice from
  original source to a new area becomes compacted
  or cemented into solid rx
• Chemical- Sedimentary rx when dissolved minerals
  in water fall out of solution (precipitate out)
  solute is usually water
• Organic- Sedimentary rx that form from the
  remains of once living organisms

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Clastic Sediments

• Conglomerates- sed rx composed of rounded gravel,
  cobbles or pebble fragments that are cemented
  together by water flowing between the cobbles
• Breccias-conglomerates created when angular rx
  are cemented together during a mud flow
• Sandstones- sed rx composed of sand sized grains
  that are cemented together typically made up of
  quartz sands
• Shale- sed rx composed of clay sized particles
  that have been cemented and compacted together
  under pressure into flat layers

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Examples of Clastic Sediments
Breccia
Conglomerate
Sandstone
Shale
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Chemical and Organic Sediments

• Evaporites- dissolved minerals left behind to
  form rocks some minerals dissolve in water and
  reform to create rocks
• Gypsum and Halite (salt flats)
• Coal- made of mostly hydrocarbons from the
  burial, heating and compaction of organic
  material
• Limestone-forms from the collection and
  compaction of the shells of marine organisms
  (corals, clams, plankton, etc.)
• Aragonite is the main component
• Fossils-the remains or traces of plants and
  animals typically preserved in sed rx. often
  only the impressions are left

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Sedimentary Rock Features

• Stratification- the layering of sed rxs whenever
  there is a change in the type of sed being
  deposited or when change in deposit direction or
  the amount of time of layering
• Bedding, or horizontal layering, is the primary
  feature of sedimentary rocks.
• Cross bedding typically from wind blown
  deposits creates feather-like patterns
• Graded-bedding occurs when grain size varies
  during deposition

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Examples of Sedimentary Features
Cross bedding
Graded bedding
Fossil Fish
Fossil Plant Impressions
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Section Assessment

• Match the following terms with their definitions.
• ___ clastic
• ___ deposition
• ___ lithification
• ___ bedding

A. horizontal layering of sedimentary
rocks B. the physical and chemical processes that
transform sediments into sedimentary
rocks C. rock and mineral fragments produced by
weathering and erosion D. occurs when sediments
are laid down on the ground or sink to the
bottoms of bodies of water
C D B A
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Section Assessment

• Identify whether the following statements are
  true or false.

________ Cementation is a form of
lithification. ________ During deposition, the
largest particles end up in the top
layer. ________ Graded bedding is often observed
in marine sedimentary rocks. ________ Clastic
sediments can range in size from microscopic
particles to huge boulders.
true false true true
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Section Assessment

• The following are which type of sedimentary
  rock?
• ___ coal
• ___ sandstone
• ___ limestone
• ___ shale
• ___ conglomerate
• ___ rock gypsum
• ___ breccia

A. clastic B. chemical C. organic D. A and B E. B
and C
C A E A A B A
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More Sedimentary Features

• Ripple marks- wave-like features created by the
  action of moving water or wind on sand
• Mud Cracks- the fossilization of mud after it has
  dried and shrunk, creating cracks found at
  rivers, flood plains, or dry lake beds
• Concretions- areas in sedimentary layers where
  minerals have precipitated from solution around
  an existing rock particle these tend to be
  different than the rock around them

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Sedimentary Rock Features
Stratification
Ripple marks
Concretion
Mud Cracks
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Causes of Metamorphism

• Metamorphic rock forms when high temperature and
  pressure combine to alter the texture,
  mineralogy, or chemical composition of a rock
  without melting it.
• The high temperatures ultimately are derived from
  Earths internal heat.
• The high pressures can be generated in two ways
• From vertical pressure caused by the weight of
  overlying rock
• From the compressive forces generated as rocks
  are deformed during mountain building

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Metamorphism Three Ways

• Contact Metamorphism- occurs when moving magma,
  lava or hot liquid comes into contact with rock
  and only changes rocks near or actually touching
  the hot material
• Regional Metamorphism- metamorphism that occurs
  over a large area (1000km2) due to the movement
  of tectonic plates past one another
• Hydrothermal metamorphism occurs when very hot
  water reacts with rock and alters its chemistry
  and mineralogy.

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Contact Metamorphism
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Contact Metamorphism

• High temperature and moderate-to-low pressure
  form the mineral assemblages that are
  characteristic of contactmetamorphism
• Because temperature decreases with distance from
  an intrusion, metamorphic effects also decrease
  with distance.

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Two Types of Metamorphics

• Nonfoliated- meta rx that do not have definite
  layers or bands often have a coarse grained
  texture
• Marble- metamorphosed limestone
• Quartzite- metamorphosed sandstone

• Foliated-meta rx that have bands of minerals that
  are parallel to one another
• Slates-metamorphosed shale
• Schist-metamorphosed slate
• Gneiss- light and dark bands of crystals

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Examples of Metamorphic Rx
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Metamorphic Textures

• Porphyroblasts

• Under certain conditions, new metamorphic
  minerals can grow quite large while the
  surrounding minerals remain small.
• Porphyroblasts are large crystals, which can
  range in size from a few millimeters to a few
  centimeters.

• Porphyroblasts are found in areas of both contact
  and regional metamorphism.