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Sedimentology and Stratigraphy > (T?) Storms and Ocean Currents > Flashcards

(T?) Storms and Ocean Currents Flashcards

1
Q

What is the name for the marine zone which exists to the edge of the continental shelf?

A

Neritic zone

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2
Q

What is the name of the point between the bathyal zone and the neritic zone?

A

Shelf edge break

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3
Q

What is the name for the marine zone which exists from the edge of the continental shelf to the abyssal plain?

A

The Bathyal zone

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4
Q

What would the standard ratio for a typical continental shelf slope (range)

A

1:40 to 1:1000

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5
Q

How far out can continental shelves go? (range)

A

10’s - 100’s km

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6
Q

How steep is the continental slope? (range)

A

2 - 7 degrees

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7
Q

What is the name for the point where the bathyal zone meets the abyssal zone?

A

Continental rise

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8
Q

What is the name for the marine zone which exists beyond the bathyal zone?

A

Abyssal zone

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9
Q

Where does the transition between oceanic and continental lithosphere begin?

A

Continental rise

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10
Q

What is the expected depth of the shelf edge break?

A

200m

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11
Q

What is the expected depth of the continental rise?

A

400m

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12
Q

What is the primary difference between a epicontinental sea and a normal ocean?

A

Epicontinental seas exist on continental crust

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13
Q

Give an example of an epicontinental sea

A

Gulf of Carpentaria - Inlet of Arafura Sea at the top of Australia

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14
Q

What is the “Hadal Zone”?

A

The marine zone below 4000m

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15
Q

What is the name for the marine zone beneath 4000m

A

Hadal zone

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16
Q

What are the four devisions in the netric zone?

A

Foreshore, Shoreface, Off-shore transition, Offshore

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17
Q

What is the name for the zone between mean high water and mean low water?

A

Foreshore

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18
Q

What is the name of the zone between the mean low water and the fair weather base?

A

Shoreface

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19
Q

What is the name of the zone between the fair weather base and the storm weather base?

A

The Offshore Transition

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20
Q

What is the name of the zone below the Offshore Transition?

A

Offshore

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21
Q

What defines the foreshore?

A

Mean high water and mean low water

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22
Q

What defines the shoreface?

A

Zone between mean low water and fair weather base

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23
Q

What defines the off-shore transition?

A

Zone between the fair-weather base and the storm weather base

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24
Q

What defines the offshore zone?

A

Zone below the storm-weather base

25
What is a typical range of depths for the fair-weather base?
~5 - 20 m
26
What is a typical range of depths for the storm-weather base?
~20 - 200 m
27
What is the likley scenareo where the storm-weather base is up to 200m deep?
Shelf boarders an ocean with larger fetch for storm waves
28
What is a typical windspeed in a storm?
>100km/hr
29
What are the three components of the storm effect on shelf environments?
Wind drive currents deeper, high energy = sed into suspension, gravity driven underflow producing tempestites
30
What are tempestites?
A rock which shows evidence of a strong storm because it has redeposited pre-existing sediments
31
What does tsunami mean in Japanese?
Harbor Wave
32
What is the typical range for the periods of a tsunami?
10^3 - 10^4 seconds
33
Theoreticaly, what should a tsunami deposit show? (2)
Poorly mixed debris and fauna from various coastal/shallow marine sources
34
What does "geostrophic" mean?
Windblown currents
35
Why are the effects of geostrophic driven currents most noticable in deeper waters?
Tides, waves and storms mask the effects in shallower environments
36
What is the main sedimentary action of geostrophic currents?
Moving fine sediment in suspension
37
How is the upwelling in the thermohaline important for sedimentology?
High nutrience and thus high biogenic activity
38
What does authogenic mean?
A mineral/sedimentary rock which is generated where it is found - i.e. not deposited
39
What is Glauconite and how does it form?
Potassium rich mica (dark green mineral) which is authogenic, and crystalizes in a sedimentary environment
40
What are the four materials which contribute to glauconitisation?
Hard parts of forams, Carbonate fragments, Faecal pellets, lithic fragments
41
What macroenvironment is required for glauconitisation? What depth is this?
Interface between oxidising seawater and reducing intertidal waters, Typically 50-500m depth
42
What zone does glauconitisation usually occur within?
Between the Neritic Zone and the Bathyal Zone
43
What is glauconite a reliable indicator of? (3)
Shallow marine, Sedimentation of other material is slow, Usually precip in periods of sea level rise
44
Why is glauconite particullary useful when determining dates of sea level rise?
Potassium can be radiometrically dated
45
What is the bulk composition (>15%) of phosphorites?
P2O5
46
Where does the majority of the phosphate come from in phosphorites? (3)
Primary bioclasts: Fish teeth, Scales, Vertebrete bones
47
Aside from primary bioclasts, how else can phosphorites form?
Authogenic - grains of peloids and micronodules on sea floor
48
What is the presence of phosphorites a characteristic sign of?
Slow sedimentation, hence it is found in condensed sections
49
Where are phosphorites most commonly found in modern times?
Regions of continental margins with upwelling of nutrient rich waters (Plankton blooms)
50
Give an modern example of a location with abundance of phosphorites
W. African coast from Antarctic waters
51
When in geological history is it expected that phosphorite concentrations were at their greatest and why?
When sea level was at its highest and supply of other sediment to she shelf is reduced
52
What is another name for pelagic sediment and what % carbon does it contain?
1-15% organic carbon, Black shale
53
What is often found in the same environment as black shale?
Pyrite (Iron sulphate)
54
How does black shale form?
Organic material falling to the sea floor, may become oxygenated by currents, falls into an anoxic environment
55
What are the three characteristics which determine the formation of black shale?
Organic imput, breakdown by microbial activity, dilution of additional materials
56
What is a good modern example of black shale formation?
The Black Sea
57
What is required for Black Shale formation even when circulation on shelves is effective?
Supply of material needs to be greater than the rate of breakdown
58
Why is black shale so important today?
Hydrocarbon source

Sedimentology and Stratigraphy (19 decks)

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