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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
Q

Name three landslide/rockfall triggers

A

Undercutting at base, Earthquakes, Waterlogging

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26
Q

Name the five types of downslope movement

A

Landslide, Rockfall, Soil Creep, Slumping, Debris Flow

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27
Q

Where does scree and talus cones form?

A

Mountainous areas

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28
Q

What are the relevant characteristics of scree/talus cones?

A 
Poorly sorted
Crudely stratified (bedding may be retained at 30 degrees angle)
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29
Q

What is sheet wash?

A

Unconfined surface run-off down a slow following rain

30
Q

What are the four variables of sheet wash

A

Rainfall amount, slope steepness, vegetation, porosity

31
Q

Where is surface runoff most effective? (5 variables)

A

Flash-flood, steep slope, impermeable, sparsely vegetated, arid

32
Q

Define “denudation”

A

Lowering of land by erosion and transport

33
Q

Why does an increase in relief cause an increase in denudation?

A

Transport processes more efficient

34
Q

What are the two essential variables in chemical weathering?

A

Water and temperature

35
Q

What is the contradicting factor when it comes to hot tropical regions and weathering?

A

Water and warmth induce very rapid weathering, yet often dense vegetation and thus less erosion

36
Q

What is the relationship between a lack of vegetation and chemical weathering?

A

Rainfall has little residence time and thus less time for weathering

37
Q

How does weathering operate in polar/mountain climates?

A

Chemical weathering: slow

Physical weathering: effective

38
Q

Where is wind ablation an important transportation process?

A

Dry regions: arid deserts and cold/polar/mountainous regions - sparse vegetation

39
Q

What is the weathering regime like in temperate regions?

A

High vegetation - low eroison

Weathering generally subdued

40
Q

Limestone weathers __x faster in ___ and ___ regions?

A

10x, Temperate, Tropical

41
Q

If climate remains the same, what is the greatest variability in chemical weathering?

A

Different lithologies

42
Q

Give an example of a quick weathering rock

A

Mafic rocks

43
Q

Give an example of a slow weathering rock

A

Quartz rich rocks

44
Q

Large amounts of __ is commonly generated at island arcs in ___/___ rocks

A

Clay, Basaltic/Andesitic

45
Q

Extreme chemical weathering gives rise to deep ___

A

Laterites

46
Q

What is the karst system?

A

Cave and canyons formed by the dissolution of limestone

47
Q

What is the relationship between limestone and sand?

A

Sand is largely absent in karst systems due to dissolution

48
Q

What is the relationship between limestone and conglomerates?

A

May form at the site of erosion but most material is lost to solution

49
Q

What is the relationship between soil profile thickness and water? (4 points)

A
  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
Q

How does the destruction of vegetation in tropical areas induce high rates of erosion/transportation?

A

Deeply weathered material from the vegetation becomes loose and easy to transport

51
Q

What was earth like pre-silurian?

A

No land vegetation - high denudation rates

52
Q

When did plant life begin to appear on earth?

A

Silurian

53
Q

What was plant life like from the Silurian to the Mid-Cretaceous?

A

Ferns, conifers, lycopods - simple root systems with limited binding

54
Q

When in earths history was plant life limited to simple root systems?

A

Silurian to Mid-Cretaceous

55
Q

What was plant life like from the Mid-Cretaceous to the Mid-Cenozoic?

A

Angiosperms more important, complex root systems with good binding

56
Q

When in earths history did plant life begin to evolve angiosperms?

A

Mid-Cretaceous

57
Q

What was plant life like after the Mid-Cenozoic?

A

Grass evolution, widespread plants, large land areas with dense fibrous root system

58
Q

How does equilibrium become achieved in the tectonic/denudation relationship?

A

Erosion reduces mass, plateau becomes uplifted - process reoccurring until equilibrium

59
Q

What is a “rain shadow”?

A

Rain on windward side of mountain, dry wind on the leeward side

60
Q

Give an example of a modern day rain shadow

A

The Tibetan Plateau

61
Q

What is “thermochronology”?

A

Temperature history of rocks

62
Q

Describe fission track dating for apatite

A
  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
Q

Describe fission track dating for zircon

A
  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
Q

How does one convert thermo-chronology into rates of erosion?

A
  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
Q

What grain size is best for undergoing provenance studies?

A

Clastic material - clasts can represent particular bedrock lithologies much easier

66
Q

What type of mineral is key to determining source bedrock?

A

Heavy minerals

67
Q

Give five examples of heavy minerals found in acidic igneous rocks

A

Apatite, Zircon, Biotite, Magnetite, Hornblende

68
Q

Give four examples of heavy minerals found in basic igneous rocks

A

Rutile, Augite, Ilmenite, Hypersthene

69
Q

Give five examples of heavy minerals found in high rank metamorphic rocks

A

Garnet, Kyanite, Silliminite, Staurolite, Epidote

70
Q

Give five examples of heavy minerals found in low rank metamorphic rocks

A

Tourmaline, Biotite

71
Q

Give two examples of heavy minerals found in sedimentary rocks

A

Reworked minerals, eg. rounded Zircon grains, rounded Tourmaline grains

72
Q

What can be told about a providence from a sample of mud in a river?

A

Fingerprinting of entire basin composition - potentially entire continental area

Sedimentology and Stratigraphy (19 decks)

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