CHPTR 5/6 Sedimentary Rocks Flashcards
1
Q
weathering
A
physical /chemical breakdown of rock at or near the surface of the Earth to produce sediment
2
Q
mass wasting
A
transfer of material downhill under influence of gravity
3
Q
Transport of sediment types
A
mass wasting
erosion
4
Q
lithification
A
sediment turns into sedimentary rock
5
Q
erosion
A
movement by water, ice or wind
6
Q
deposition
A
sediment reaching a location where it accumulates
7
Q
detrital sediment
A
final product of mechanical weather
8
Q
3 types of mechanical weathering
A
frost wedging, sheeting, biological activity
9
Q
how does mechanical weathering affect chemical weathering
A
mechanical weathering creates more surface area which makes chemical weathering more effective
10
Q
frost wedging
A
water enters the cracks of rocks and expands by 9% when it freezes
- this creates pressure and causes the rocks to break
11
Q
talus
A
broken rock that has fallen from mountains because of frost wedging
12
Q
sheeting
A
mechanical weathering where the rock breaks into sheets - granite at the surface
13
Q
what causes sheeting
A
pressure releases
temp. cycle from day to night and winter to summer
14
Q
biological activity
A
tree roots, geology students, etc
15
Q
3 types of chemical weathering
A
dissolution, oxidation, hydrolosis
16
Q
end result of chemical weathering
A
ions dissolved in water - chemical sediment
17
Q
dissolution
A
chemical weathering where the water molecules are polar, electrostatic forces allow ions to be removed from solid
thus water dissolves rock
18
Q
what acid is in acid rain and how is it relevant to chemical weathering
A
carbonic acid H2CO3 - acid increases the effects of dissolution
19
Q
oxidation
A
rusting -
chemical weathering where rocks containing iron minerals breakdown when exposed to the atmosphere - the atoms dissociate
20
Q
hydrolysis
A
hydrogen ions react with and replace positioive ions in potassium feldspare.
21
Q
what does hydrolysis form
A
clay minerals and potassium and silica in a solution
3D framework > sheet silicate
feldspar > kaolinite
22
Q
what is kaolinite used for
A
(mineral) used in China pots
23
Q
spheroidal weathering
A
in chemical weathering, sharp corners have more surface area so weathering will occur faster there. This leads to rounded shapes
24
Q
Bowen’s Reaction series
A
high to low melting temperature
(first to crystallize)
olivine
pyroxene/calcium feldspar
amphibole
biotite/sodium feldspar
potassium feldspar
muscovite
quartz
25
Order of mineral's suseptibilitiy to chemical weathering
Bowen's reaction series
least resistant to most
olivine
pyroxene/calcium feldspar
amphibole
biotite/sodium feldspar
potassium feldspar
muscovite
quartz
26
effects of climate on type of weathering
strong chemical - hot and wet
strong mechanical - cold and wet
27
boulder size range
>256mm
28
cobble/gravel size range
64 - 256mm
29
pebble size range
4-64mm
30
granule
2-4mm
31
sand size range
1/16 - 2mm
32
silt/mud size range
1/16 - 1/256mm
33
clay size range
<1/256mm
34
what particle sizes form conglomerate and breccia
boulder
cobble
pebble
granule
35
what particles sizes form sandstone
sand
36
what particle sizes form mudrocks
silt/mud and clay
37
most common minerals for clasts
quartz, feldspar, clay minerals
38
sorting
poorly sorted - many sizes in one sample
very well sorted - all same sizes in one sample
39
how is sediment affected by transportation
sorting improves - heavies particles drop sooner
roundness increases - grains abrade each other
40
continental depositional environments
glacial deposits, streams - alluvial fans, wind - sand dunes, salt lakes
41
transitional depositional environments
tidal flats, beaches, spit, lagoons, deltas
42
marine depositional environments
continental shelf - shallow
continental slope - deep
43
colluvial sediments + features
transported by gravity
- poorly sorted
- angular
44
alluvial sediments + features
transported by water
- well sorted
- rounded
45
aeolian sediments + features
transported by wind
- well sorted
- heavier particles are distributed first
46
loess
a structure made up of wind-blown dust that's mostly silt-sized particles
47
glacial sediments
transported by ice
48
glacial till
clay formed under glacier ice
49
morraine
mixture of boulders, gravel, sand, and clay carried on top of ice (poorly sorted)
50
soil formation depends on (5)
1. parent material
2. time
3. climate
4. plants and animals
5. topography
51
unconfined compressive strength of bedrock
>1 MPa
52
unconfined compressive strength of regolith
< 1 MPa
53
regolith
unconsolidated sediments ("engineering soil"), grains not connected, formed locally or transported from elsewhere through erosion
54
soil + ideal composition
combination of mineral and organic material
50% mineral/humus
25% air
25% water
55
where is regolith thickest
sedimentary basins and along major rivers
56
where is regolith thinnest
the Arctic
57
bedrock
residual soils
58
unconsolidated material
transported soils
59
how does parent material affect soil formation (from sediment)
parent rock is bedrock - slower formation of soil
parent rock is unconsolidated material - faster formation of soil
chemistry of the parent material controls chemistry of soil and fertility
60
how does time affect soil formation (from sediment)
initially soil composition depends on parent material
as time progresses climate begins to control composition
61
how does climate affect soil formation
determines temperature and amount of precipitation
62
how could plants and animals affect soil formation
high organic content in forest or bog
low organic content in desert
fungi, bacteria, worms all increase the rate of formation of soil
63
how does topography affect soil formation
- low moisture content on a steep slope
- soil gets moved downhill by erosion so area no longer has soil
- lowlands have higher moisture and more time for soil to develop
64
if i have 50% mineral, 25% air, 25% water, what is the porosity of my sample
50% - half of the gaps are just filled with water
65
most important factor of soil formation
climate
66
downward sequence of soil horizons
O, A, E, B, C
67
o horizon
Organic. varies from dead leaves to decomposed material. full of microscopic life
68
a horizon
mineral matter - up to 30% humus
69
E horizon
lEached horizon. light coloured layer with little organic material. Percolation of water causes eluvation. Other chemicals transported through leaching
70
B horizone
subsoil. material from E- horizon is deposited here
71
C horizon
altered parent material
72
which soil layers are the top soil
O and A
73
pedalfer
soil type
precipitation greater than evaporation+transpiration (wet/humid)
(think of the Boreal forest)
enough vegetation to produce acid conditions for leaching
74
pedocal
soil type
precipitation less than evaporation+transpiration (dry/grassland)
75
what happens to calcium carbonate in pedocal
not leached downwards, can be drawn upwards and precipitated
76
what happens to calcium carbonate in pedalfer
vegetation produces acid conditions that allow the calcium carbonate to be leached downwards
77
laterite
soil type
develops in hot, wet tropical climates
78
what happens to calcium carbonate in laterite
very intense leaching
79
what colour is laterite and how is it agriculturally
red due to concentrated aluminum and iron.
bad for agriculture due to minimal humus
80
chernozemic
grassland soil - pedocal
81
luvisolic
boreal forest - pedalfer
82
cryosolic
permafrost - mature soil does not develop - tundra
83
diagenesis
change in rock temperature within 150 - 200 degrees C - one type is lithification
84
lithification
compaction then cementation
85
compaction
the volume of a deposit of sediment decreases as the weight of overlying sediment causes a reduction in pore space
86
what rock can be formed purely by compaction
mud into shale
87
cementation
new mineral between grains of sediment
88
most common cementation elements
calcium, carbonate, silica, iron oxide
89
most common type of sedimentary rock
shale/mudrocks
- more than half of all sedimentary rocks
90
shale/mudrocks features
- fine grains that cannot be seen
- brittle
- low permeability
91
second most abundant sedimentary rock
sandstone
92
sandstone features
poorly sorted to very well sorted
sharp edges
made of quarts, feldspars, lithic fragments
93
arenite
quartz sandstone
94
arkose
>25% feldspar sandstone - found near granite was weathered
95
greywacke + sorting
quartz, feldspar, lithic fragments make up the sandstone - associated with turbidity currents
poorly sorted
96
conglomerate
>2mm rock fragments in cement - rounded
97
breccia
>2mm rock fragments in cement - angular
98
3 inorganic mechanisms to convert chemical sediment into sedimentary rocks
evaporation, dripping, chemical processes
99
organic mechanism to convert chemical sediment into sedimentary rocks (biochemical)
aquatic organisms
100
what % of sedimentary rocks is limestone
10% + most abundant chemical sedimentary rock
101
is limestone a chemical or mechanical sedimentary rock
chemical and organic
102
types of organic limestone
fossiliferous, chalk
103
types of inorganic limestone
travertine, oolitic
104
what is the highest mineral percentage in limestone
Calcite
105
what forms fossiliferous limestone
polyps (reefs) turn CaCO3 into shells.
106
chalk is formed by + features + what does chalk form
formed as microorganisms shed small plates
porous and resistant to erosion
forms steep cliffs
107
travertine
limestone formed along streams, when CaO3 is is deposited when the water is evaporated, leaving a supersaturated solution
108
oolitic limestone
limestone made of spherical grains of CaO3
109
dolostone formation
direct precipitation from seawater
110
chert
silica + quartz dissolved in water
plankton convert into rocks
111
evaporites
as concentration of salt increases, crystal precipitated in sequence
1. carbonates (calcite, dolomite)
2. sulphates (gypsum, anhydrite)
3. halite
4. potassium salts (sylvite)
(least to most bitter)
112
when water is lost this mineral turns into anhydrite
gypsum
113
successive stages in the formation of coal
peat, lignite, bituminous, anthracite
114
peat
partially altered plant material
caused by burial in swamp environment
115
lignite
soft, brown coal
caused by compaction of peat
116
bituminous
soft black coalant
caused by greater compaction of lignite
117
anthracite
hard black coal
caused by metamorphism of bituminous
118
strata
horzontal lines - formed as sediments are most commonly deposited flat in water
119
bed
strata with a thickness > 1cm
120
laminae
strata with a thickness < 1cm
121
bedding plane
the separation of layers of strata
122
crossbedding
characteristic of sand dunes, river deltas.
preserves layers deposited at an angle
123
graded beds
continental shelf avalanche, largest particles settle first, smaller particles settle last. creates greywacke
124
ripple marks shallow water - back and forth current
symmetrical ripples
125
ripple marks deeps water - current
angled ripples
126
rythmites
thin and thick strips - tidal cycle causes a different layer per day
127
varves
rock stripes - coarse sediment in the summer, fine in the winter creates layers
128
crystalline basement
igneous and metamorphic rocks that underlay a surface layer of sedimentary rocks
129
mudcracks form only
above sea level
130
131
4 reasons sedimentary rocks are economically significant
1. hydrocarbon resources
2. hyrdologic resources
3. uranium deposits
4. iron
132
3 reasons sedimentary rocks are scientifically significant
1. record of evolution by preserving fossils
2. record past climate
3. record past earthquakes
133
what percentage of the crust is sedimentary rocks by volume
5-10%
134
what percentage of the crust is sedimentary rocks by surface area
75%
135
order of mineral precipitation in evaporite formation
1. Carbonates (dolomite, calcite)
2. Sulphates (gypsum, anhydrite)
3. Halites (rock salt)
4. Potassium Salts (potash)
(gets more "salty")
