Download Sedimentary rock Sed rocks account for about 5 % of Earth`s

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Sedimentary rock
Rock formed by evaporation or by the accumulation and consolidation
of sediments
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Sed rocks account for about 5 % of Earth’s outer 10 miles
"Sediments" may include:
Rock fragments
Plant fragments
Animal fragments
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Significance of Sedimentology
Sedimentary rocks contain:
• Coal, petroleum, natural gas
• Gypsum, salt, limestone, etc.
• Groundwater
• Our planet’s evolutionary history! (fossils)
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Two Types
Clastic
=Detrital
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Chemical
Lithification of Clastic Rocks
the process by which soft, loose sediment is converted into sedimentary rock
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Two Methods of Lithification
Cementation
Compaction
Silica
Calcite
Iron oxides
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Chief constituents of sedimentary rocks
Quartz, Feldspars, Micas, Clay minerals
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Clastic sedimentary rocks
Particle size is used to distinguish among the
various types of detrital rocks
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Particle size is used to distinguish among the various types of detrital rocks – see Table 6.2
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What happens to sediments during transport?
1) Rounding
Waves and rivers rework grains
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What happens to sediments during transport?
1) Rounding
Waves and rivers rework grains
The grains hit and grind against
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each other
What happens to sediments during transport?
1) Rounding
Waves and rivers rework grains
The grains hit and grind against
Angular grains turn into
each other
rounded grains
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Picture of rounding and sorting
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What happens to sediments during transport?
2) Sorting
Grains are separated according to grain
size, shape, and density
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Picture of rounding and sorting
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Common detrital sedimentary rocks
In order of increasing particle size:
1)Shale
2)Sandstone
3)Conglomerate
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1) Shale (detrital; clastic)
– Most common sedimentary rock
– Mud-sized particles in thin layers = lamin(e)a
– May lose 80% of volume during compaction
– Varied depositional environments
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Shale containing plant remains
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Sedimentary Environments
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2) Sandstone (detrital; clastic)
Forms in a variety of environments
–Commonly well-sorted, well-rounded grains
–Quartz is the predominant mineral (>90%)
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Picture of Navajo sandstone, fig. 6.4
Close-up picture of sandstone
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Microscope image of sandstone
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3) Conglomerate and Breccia (detrital; clastic)
– Both are composed of particles greater than 2 mm in diameter
– Conglomerate: rounded gravels
– Breccia :large angular particles
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Picture of cobbles and pebbles on a stream bank
Picture of conglomerate
Breccia
Chemical Sedimentary Rock
DEF.: rock formed from chemical precipitation or biologic activity
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Chemical sedimentary rocks
Precipitation occurs by:
• Inorganic
• Organic (biochemical)
processes
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Common chemical sedimentary rocks
1) Limestone (organic or inorganic)
– Most abundant biochemical rock
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Common chemical sedimentary rocks
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1) Limestone (organic or inorganic)
– Most abundant biochemical rock
– Composed chiefly of calcite (CaCO3)
Common chemical sedimentary rocks
1) Limestone (organic or inorganic)
– Most abundant biochemical rock
– Composed chiefly of calcite (CaCO3)
– Organisms take Ca from water and precipitate calcite;
their skeletons are calcite!
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Fossiliferous limestone
2) Coquina (organic limestone)
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Picture of living coral
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Coquina (organic, clastic limestone)
3) Chalk (organic)
• Microscopic organisms
• Microscopic variety of a bioclastic
limestone
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Picture of Foraminifera
4) Inorganic limestone
Includes travertine and oolitic
limestone (oolite)
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Dripstone
Picture of Ooids forming oolite
5) Chert (organic or chemical)
Microcrystalline quartz (SiO2)
Varieties include flint and jasper (banded form is called agate)
From single-celled animals and plants; radiolarans and diatoms produce silica
shells
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Jasper
Radiolarians picture
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6) Evaporites (chemical)
Evaporation of seawater or saline water results in
deposition of chemical precipitates
Examples: rock salt (NaCl) and rock gypsum (CaSO4 .
2H2O)
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Picture of rock salt
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7) Coal (organic)
Diagram of Coal formation
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