ress sedimentary processes physical weathering
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Sedim
entary Rocks and
Sedim
entary Rocks and
Processes
Processes
Sedim
entary Processes
Sedim
entary Processes
��Weathering
Weathering
��Breakdown of pre
Breakdown of pre-- existing rock by physical and
existing rock by physical and
chemical processes
chemical processes
��Transport
Transport
��Movement of sedim
ents from environments of
Movement of sedim
ents from environments of
relatively high potential energy
relatively high potential energy
��Deposition
Deposition
��Settling of sedim
ents in environments of relatively low
Settling of sedim
ents in environments of relatively low
potential energy
potential energy
��Diagenesis
Diagenesis
��Chemical changes that occur after sedim
ents are
Chemical changes that occur after sedim
ents are
buried
buried
Sedim
entary Processes
Sedim
entary Processes
��Weathering
Weathering
��Physical Weathering
Physical Weathering
��Mechanical breaking of rock into smaller pieces (clasts)
Mechanical breaking of rock into smaller pieces (clasts)
��No new m
inerals form
ed
No new m
inerals form
ed
��Chemical Weathering
Chemical Weathering
��Reaction of rocks with air or water
Reaction of rocks with air or water
��New m
inerals form
ed at the expense of less stable m
inerals
New m
inerals form
ed at the expense of less stable m
inerals
��Transport
Transport
��Deposition
Deposition
��Diagenesis
Diagenesis
Physical Weathering
Physical Weathering
��Abrasion
Abrasion
��Grinding of rock fragments (e.g., sandblasting)
Grinding of rock fragments (e.g., sandblasting)
��Frost Wedging
Frost Wedging
��Ice is approxim
ately 8% greater volume than an equal number of m
Ice is approxim
ately 8% greater volume than an equal number of moles of
oles of
water
water
��Ice in cracks expands and creates an extensional stress
Ice in cracks expands and creates an extensional stress
��Salt Crystallization
Salt Crystallization
��Salt crystals that precipitate in cracks due to evaporation of s
Salt crystals that precipitate in cracks due to evaporation of saline
aline
solutions will expand when heated and create stress
solutions will expand when heated and create stress
��Exfoliation
Exfoliation
��Rock breaks apart in layers that are parallel to the earth's sur
Rock breaks apart in layers that are parallel to the earth's sur face
face
due to expansion when overlying m
aterial is eroded
due to expansion when overlying m
aterial is eroded
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Abrasion of Brownstone
Abrasion of Brownstone
Frost Wedging of Brownstone
Frost Wedging of Brownstone
Chemical Weathering
Chemical Weathering
��Dissolution
Dissolution
��HH
22CO
CO
33+
+ C
aCO
CaCO
33→→
Ca
Ca2+
2+(aq)
(aq) + 2HCO
+ 2HCO
33--(( aq
aq))
��Dissolution of calcite in carbonic acid
Dissolution of calcite in carbonic acid
��All rainwater is a weak carbonic acid solution
All rainwater is a weak carbonic acid solution
��CO
CO
2 (g)
2 (g)+ H
+ H
22O
O (l)(l)↔↔
HH22CO
CO
3(aq)
3(aq)↔↔
HH+
+ (( a
qaq))+ HCO
+ HCO
33--(aq)
(aq)
��NaCl
NaCl→→
Na
Na++
(( aq
aq))+ Cl
+ Cl--
(( aq
aq))
��Dissolution of halite in water
Dissolution of halite in water
��Would you expect to find halite in outcrop?
Would you expect to find halite in outcrop?
��Would calcite be more resistant in wet or dry climates?
Would calcite be more resistant in wet or dry climates?
Dissolution of Marble from Acid Rain
Dissolution of Marble from Acid Rain
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Chemical Weathering
Chemical Weathering
��Hydrolysis
Hydrolysis
��In hydrolysis a m
olecule is split into two parts by reacting wit
In hydrolysis a m
olecule is split into two parts by reacting with water.
h water.
One product includes an O
HOne product includes an O
H--from the water molecule, whereas H
from the water molecule, whereas H
++is
is
added to another
added to another
��Mg
Mg22SiO
SiO
44+ 4H
+ 4H
+++ 4OH
+ 4OH
--⇌⇌
2Mg
2Mg2+
2+(aq)
(aq)+ 4OH
+ 4OH
--+ 4H
+ 4H
44SiO
SiO
44(( aq
aq))
��Hydrolysis of
Hydrolysis of olivine produces a solution
olivine produces a solution(m
ineral dissolves)
(mineral dissolves)
��2KAlSi
2KAlSi 33OO
88+ 2H
+ 2H
22CO
CO
33+ 9H
+ 9H
22O
O ⇌⇌
Al
Al 22Si
Si 22OO
55(O
H)
(OH) 44
+ 4H
+ 4H
44SiO
SiO
44(( aq
aq))+ 2K
+ 2K
+++ 2HCO
+ 2HCO
33--
��Hydrolysis of
Hydrolysis of KK-- feldspar produces
feldspar produces kaolinite
kaolinite(clay product)
(clay product)
��What would happen to
What would happen to albite
albiteor or anorthite
anorthitedue to hydrolysis?
due to hydrolysis?
��What would happen to a granite in warm and wet environments?
What would happen to a granite in warm and wet environments?
��Where do the dissolved ions (e.g., Mg
Where do the dissolved ions (e.g., Mg2+2+, K, K++) go?
) go?
++
++
→+
+)
(4
48
10
44
28
34
4)
(4
84
aq
KSiO
HOH
OSi
Al
HO
HO
KAlSi
++
++
→+
+)
(4
48
10
44
28
34
4)
(4
84
aq
KSiO
HOH
OSi
Al
HO
HO
KAlSi
++
++
→+
+)
(4
48
10
44
28
34
4)
(4
84
aq
KSiO
HOH
OSi
Al
HO
HO
KAlSi
SilicicAcid
(Dissolved Silica)
Chemical Weathering
Chemical Weathering
��Oxidation
Oxidation
��4FeS
4FeS
22+ 15O
+ 15O
22+ 22H
+ 22H
22O
O →→
4FeO(O
H) + 8SO
4FeO(O
H) + 8SO
4422--+ 16H
+ 16H
++
��Oxidation of pyrite to form
lim
onite
Oxidation of pyrite to form
lim
onite
��4 FeSiO
4 FeSiO
3(s)
3(s)+ O
+ O
2(g)
2(g)+ 8H
+ 8H
22O
O →→
2Fe
2Fe22OO
3(s)
3(s)+ 4H
+ 4H
44SiO
SiO
4(aq)
4(aq)
��Oxidation and hydrolysis of pyroxene to form
hematite
Oxidation and hydrolysis of pyroxene to form
hematite
��What color will a mafic igneous rock become as it weathers at th
What color will a mafic igneous rock become as it weathers at the e
surface?
surface?
��What will happen to a granite that contains pyrite as it weather
What will happen to a granite that contains pyrite as it weather s s
at the surface?
at the surface?
Oxidation of Pyrite in Sandstone
Oxidation of Pyrite in Sandstone
Oxidation Rind in Sandstone Cobble
Oxidation Rind in Sandstone Cobble
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Bowen
Bowen’’ s Reaction Series
s Reaction Series
and Chemical Weathering
and Chemical Weathering
Which m
inerals will be m
ost resistant to chemical weathering processes?
Chemical Weathering
Chemical Weathering
Start with feldspars and Fe-bearing
silicates…
End with clays, lim
onite, hematite,
and a loss of Si, Ca, Na, and K into
solution
Sedim
entary Processes
Sedim
entary Processes
��Weathering
Weathering
��Transport
Transport
��Movement of sedim
ents from environments of
Movement of sedim
ents from environments of
relatively high potential energy
relatively high potential energy
��Moved by w
ind or water
Moved by w
ind or water
��Sorted and stratified
Sorted and stratified
��Relatively fine
Relatively fine-- grained (sand by air; pebbles by water)
grained (sand by air; pebbles by water)
��Moved by glacier or gravity flow
Moved by glacier or gravity flow
��Unsorted and
Unsorted and unstratified
unstratified
��Clay to boulders
Clay to boulders
��Deposition
Deposition
��Diagenesis
Diagenesis
Sorted
Sorted vs
vsUnsorted Sedim
ents
Unsorted Sedim
ents
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Sedim
entary Processes
Sedim
entary Processes
��Weathering
Weathering
��Transport
Transport
��Deposition
Deposition
��Settling
Settling
��Sedim
ent grains stop m
oving when there is insufficient
Sedim
ent grains stop m
oving when there is insufficient
energy to m
ove them farther
energy to m
ove them farther
��Precipitation
Precipitation
��Growth of new m
inerals from oversaturated water
Growth of new m
inerals from oversaturated water
��Diagenesis
Diagenesis
Graded
Graded
Bedding
Bedding
(Fining Up)
(Fining Up)
Deposition by Precipitation
Deposition by Precipitation
(Chemical Sedim
ents)
(Chemical Sedim
ents)
��Norm
al seawater has a salinity of 35g/kg
Norm
al seawater has a salinity of 35g/kg
��Only 6 ions comprise 99% of the ions dissolved in seawater:
Only 6 ions comprise 99% of the ions dissolved in seawater:
��Cl
Cl--
55.04 wt%
55.04 wt%
��Na
Na++
30.61 wt%
30.61 wt%
��SO4
SO422--
7.68 wt%
7.68 wt%
��Mg
Mg2+
2+
3.69 wt%
3.69 wt%
��Ca
Ca2+
2+
1.16 wt%
1.16 wt%
��KK++
1.10 wt%
1.10 wt%
��Marine precipitates will be composed of these ions.
Marine precipitates will be composed of these ions.
��What minerals form as marine precipitates?
What minerals form as marine precipitates?
��Where did K, Na, Ca, and Mg come from?
Where did K, Na, Ca, and Mg come from?
��Why is Fe not abundant in seawater?
Why is Fe not abundant in seawater?
Deposition by Precipitation
Deposition by Precipitation
(Chemical Sedim
ents)
(Chemical Sedim
ents)
6.15
6.15
NaCl
NaCl
Halite
Halite
7.38
7.38
CaCl
CaCl 22●●6H
6H
22OO
-----
-----
0.001
0.001
MgCO
MgCO
33Magnesite
Magnesite
0.0154
0.0154
CaSO
CaSO
44●●2H
2H
22OO
Gypsum
Gypsum
0.00014
0.00014
CaCO
CaCO
33Calcite
Calcite
Solubility (mol/l)
Solubility (mol/l)
Composition
Composition
Mineral
Mineral
Why is CaCl
CaCl 22●●6H6H22O not a naturally occurring
O not a naturally occurring evaporite
evaporitemineral?
mineral?
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Chemical Sedim
ents
Chemical Sedim
ents
��Lim
estone are the m
ost common chemical
Lim
estone are the m
ost common chemical
sedim
ent
sedim
ent
��Common in shallo
w, tropical, m
arine
Common in shallo
w, tropical, m
arine
environments
environments
��Evaporites (deposits of gypsum and halite)
Evaporites (deposits of gypsum and halite)
are restricted to hot, arid environments
are restricted to hot, arid environments
where evaporation rates are high
where evaporation rates are high
Lim
estone R
eef and Lagoon
Lim
estone R
eef and Lagoon
Fossiliferous Lim
estone
Fossiliferous Lim
estone
Salt Lake D
eposits (Death Valley)
Salt Lake D
eposits (Death Valley)
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Sabka
Sabka(Saudi Arabia)
(Saudi Arabia)
Gypsum Beds in Red Sandstone
Gypsum Beds in Red Sandstone
Diagenesis: Cementation
Diagenesis: Cementation
��Precipitation of minerals from solutions in pore water
Precipitation of minerals from solutions in pore water
��Composition of ground water varies greatly depending
Composition of ground water varies greatly depending
on such variables as bedrock composition and rainfall
on such variables as bedrock composition and rainfall
��Calcite and dolomite might develop in hard
Calcite and dolomite might develop in hard-- water areas
water areas
��Clays and quartz might develop in soft
Clays and quartz might develop in soft-- water areas
water areas
��Limonite and hematite may occur in rocks that are rich in iron
Limonite and hematite may occur in rocks that are rich in iron
��Pyrite may occur in rocks where the pore waters were anoxic
Pyrite may occur in rocks where the pore waters were anoxic