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Sedimentology and Stratigraphy > (S2) Sources of Sediment > Flashcards

(S2) Sources of Sediment Flashcards

1
Q

Name the three orogenic sources of sediment

A

Collision giving mountain chains
Rift Valley
Plateau from plumes pushing on buoyant plates

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2
Q

How does climate have an effect on the source of sediment?

A

Climate belts at latitudes

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3
Q

What is “regolith”?

A

Layer of loose material from weathering of bedrock

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4
Q

What are the three main types of chemical weathering?

A

Solution, Hydrolosis, Oxidation

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5
Q

What are the three main types of physical weathering?

A

Freeze thaw, Salt growth, Temp changes

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6
Q

When is freeze thaw most effective?

A

Flux temperature around 0 degrees C

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7
Q

How does the process of salt growth cause physical weathering?

A

Crystal growth in cracks

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8
Q

How does temperature changes cause physical weathering and what happens to the rock?

A

Rapid diurnal fluxes - minerals expand/contract at different rates internally
Exfoliation

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9
Q

Under what conditions are silica minerals particularly soluble?

A

Strong alkaline water

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10
Q

Under what conditions are carbonate minerals particularly soluble?

A

Strong acidic water

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11
Q

Aside from the dissolution of silica and carbonate minerals, what other process is significant in terms of solution chemical weathering?

A

Evaporite minerals (Halite, Gypsum)

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12
Q

Give an example of hydrolosis

A

Kaolinite from orthoclase + water

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13
Q

How does hydrolysis work?

A

Dissociation of H2O into H+ and OH-

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14
Q

What is the name of two acids which promote hydrolysis?

A

Carbonic Acid and Humic Acid

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15
Q

How does oxidation work?

A

Iron oxides + hydroxides from minerals containing iron

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16
Q

Name the nine silicate minerals in order of increasing resistance to chemical weathering

A

Olivine, Ca-Feldspar, Pyroxene, Amphibole, Na-Feldspar (Plagioclase), Biotite Mica, K-Feldspar (Orthoclase), Muscovite Mica, Quartz

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17
Q

What happens to quartz in physical weathering?

A

Generally separates itself from other quartz minerals and other minerals/bedrock

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18
Q

Which minerals have more chance leaving the site of weathering unaltered?

A

Biotite and below (Biotite, K-Spar [Orthoclase], Muscovite Mica, Quartz

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19
Q

Oxides of Al and Fe form what in extreme weathering conditions?

A

Laterites - A mixture of Fe and Al oxides rich soil

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20
Q

What is another name for an oxide of Al?

A

Bauxite

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21
Q

What is another name for an oxide of Fe?

A

Haematite

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22
Q

What relevance does plants have to soil development?

A

Physical breakdown, chemical changes in surface waters

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23
Q

What paleo-environment are fossil soils most commonly found within?

A

Paleo-flood plains

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24
Q

Name the four main transport mechanisms

A

Gravity, Water, Wind, Ice

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25
Name three landslide/rockfall triggers
Undercutting at base, Earthquakes, Waterlogging
26
Name the five types of downslope movement
Landslide, Rockfall, Soil Creep, Slumping, Debris Flow
27
Where does scree and talus cones form?
Mountainous areas
28
What are the relevant characteristics of scree/talus cones?
``` Poorly sorted Crudely stratified (bedding may be retained at 30 degrees angle) ```
29
What is sheet wash?
Unconfined surface run-off down a slow following rain
30
What are the four variables of sheet wash
Rainfall amount, slope steepness, vegetation, porosity
31
Where is surface runoff most effective? (5 variables)
Flash-flood, steep slope, impermeable, sparsely vegetated, arid
32
Define "denudation"
Lowering of land by erosion and transport
33
Why does an increase in relief cause an increase in denudation?
Transport processes more efficient
34
What are the two essential variables in chemical weathering?
Water and temperature
35
What is the contradicting factor when it comes to hot tropical regions and weathering?
Water and warmth induce very rapid weathering, yet often dense vegetation and thus less erosion
36
What is the relationship between a lack of vegetation and chemical weathering?
Rainfall has little residence time and thus less time for weathering
37
How does weathering operate in polar/mountain climates?
Chemical weathering: slow | Physical weathering: effective
38
Where is wind ablation an important transportation process?
Dry regions: arid deserts and cold/polar/mountainous regions - sparse vegetation
39
What is the weathering regime like in temperate regions?
High vegetation - low eroison | Weathering generally subdued
40
Limestone weathers __x faster in ___ and ___ regions?
10x, Temperate, Tropical
41
If climate remains the same, what is the greatest variability in chemical weathering?
Different lithologies
42
Give an example of a quick weathering rock
Mafic rocks
43
Give an example of a slow weathering rock
Quartz rich rocks
44
Large amounts of __ is commonly generated at island arcs in ___/___ rocks
Clay, Basaltic/Andesitic
45
Extreme chemical weathering gives rise to deep ___
Laterites
46
What is the karst system?
Cave and canyons formed by the dissolution of limestone
47
What is the relationship between limestone and sand?
Sand is largely absent in karst systems due to dissolution
48
What is the relationship between limestone and conglomerates?
May form at the site of erosion but most material is lost to solution
49
What is the relationship between soil profile thickness and water? (4 points)
1. Profile thickness gives water storage availability 2. Water storage gives rise to vegetation 3. Water storage gives rise to chemical weathering 4. Vegetation gives rise to physical breakdown
50
How does the destruction of vegetation in tropical areas induce high rates of erosion/transportation?
Deeply weathered material from the vegetation becomes loose and easy to transport
51
What was earth like pre-silurian?
No land vegetation - high denudation rates
52
When did plant life begin to appear on earth?
Silurian
53
What was plant life like from the Silurian to the Mid-Cretaceous?
Ferns, conifers, lycopods - simple root systems with limited binding
54
When in earths history was plant life limited to simple root systems?
Silurian to Mid-Cretaceous
55
What was plant life like from the Mid-Cretaceous to the Mid-Cenozoic?
Angiosperms more important, complex root systems with good binding
56
When in earths history did plant life begin to evolve angiosperms?
Mid-Cretaceous
57
What was plant life like after the Mid-Cenozoic?
Grass evolution, widespread plants, large land areas with dense fibrous root system
58
How does equilibrium become achieved in the tectonic/denudation relationship?
Erosion reduces mass, plateau becomes uplifted - process reoccurring until equilibrium
59
What is a "rain shadow"?
Rain on windward side of mountain, dry wind on the leeward side
60
Give an example of a modern day rain shadow
The Tibetan Plateau
61
What is "thermochronology"?
Temperature history of rocks
62
Describe fission track dating for apatite
1. Uranium releases alpha particle leaving a fission track through lattice 2. Crystal heated to >110 Celsius, tracks become obscured from annealing 3. Longer of period below annealing point, more fission tracks 4. Can determine at what point in the past crystal was at a certain temp
63
Describe fission track dating for zircon
1. Uranium releases alpha particle leaving a fission track through lattice 2. Crystal heated to >300 Celsius, tracks become obscured from annealing 3. Longer of period below annealing point, more fission tracks 4. Can determine at what point in the past crystal was at a certain temp
64
How does one convert thermo-chronology into rates of erosion?
1. Know thermal gradient (all fission tracks will be annealed) 2. Uplift - cools as approaches surface 3. Measurement tells us when sample was at certain depth and how long it took to erode rocks above
65
What grain size is best for undergoing provenance studies?
Clastic material - clasts can represent particular bedrock lithologies much easier
66
What type of mineral is key to determining source bedrock?
Heavy minerals
67
Give five examples of heavy minerals found in acidic igneous rocks
Apatite, Zircon, Biotite, Magnetite, Hornblende
68
Give four examples of heavy minerals found in basic igneous rocks
Rutile, Augite, Ilmenite, Hypersthene
69
Give five examples of heavy minerals found in high rank metamorphic rocks
Garnet, Kyanite, Silliminite, Staurolite, Epidote
70
Give five examples of heavy minerals found in low rank metamorphic rocks
Tourmaline, Biotite
71
Give two examples of heavy minerals found in sedimentary rocks
Reworked minerals, eg. rounded Zircon grains, rounded Tourmaline grains
72
What can be told about a providence from a sample of mud in a river?
Fingerprinting of entire basin composition - potentially entire continental area

Sedimentology and Stratigraphy (19 decks)

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