(S13) Carbonate Platforms Flashcards

1
Q

What are the five different forms of carbonate platforms?

A

Homoclinical ramp, Distally steepened ramp, Unrimmed flat-top platform, Rimmed flat-top platform, Isolated flat-top platform

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2
Q

What is an “attached flat top platform”?

A

A very low gradient top connected to the continent, then a steep slope which is the front margin: Rimmed or unrimmed

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3
Q

What is the variation in size of an attached flat top platform?

A

Few km to >1000km

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4
Q

What is another name for an inland sea?

A

Epeiric sea

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5
Q

What is a rimmed platform?

A

Carbonate shelf with a reef or other carbonate body to act as a rim before the forereef slope

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6
Q

Give three examples of facies that a lagoon created by a rimmed platform may be associated with

A

Shoals, patch reefs, migrating island systems

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7
Q

Instead of reefs, unrimmed platform margins are often marked by the development of relatively high-energy facies such as ___.

A

Ooid shoals

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8
Q

Aside from the lack of reef system, what is the two main differences between a unrimmed and a rimmed carbonate shelf?

A

Unrimmed tend to have lower gradient margins, and a somewhat higher energy platform

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9
Q

What is the variation in size of an isolated flat top platform?

A

Few hundred meters to ~500km long

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10
Q

Give a modern example of a larger isolated flat top platform

A

Bahamas

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11
Q

What is the difference between a isolated flat top platform and a reef?

A

Isolated flat top platforms may be hundreds to km above the sea-floor depth which aggrigated before reef formation

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12
Q

What defines an asymmetrical isolated flat-top platform?

A

Well-developed rimmed margin on one side of platform - usually side with prevailing wind/ocean current favourable for reef growth

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13
Q

What forms at the leeward margin of an isolated flat-topped platform?

A

Grain-shoal islands

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14
Q

What forms at the windward margin of an isolated flat-topped platform?

A

Aggrading reef

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15
Q

What is the difference between ramp platforms and other carbonate platforms? (2)

A

Not flat-topped, do not have steep margin

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16
Q

What are the two main subdivisons of carbonate ramps?

A

Homoclinal and distally steepened ramps

17
Q

What is the difference between homocline and distally steepend ramps?

A

Homoclinal = gradual gradient, Distally steepend = gradual gradient, then a margin which is slightly steeper at some distance (inner and outer ramp)

18
Q

What do the facies belts on a carbonate ramp range from?

A

Proximal tidal flats/sabkha to fine/coarse grained shoreline/lagoon to gradually finer down ramp

19
Q

What three facies can ramps be seperated into?

A

Inner, mid and outer ramp facies

20
Q

What facies can be associated with carbonate ramps? (2)

A

Patch reef systems, grainstone shoals

21
Q

Give three examples when continental interiors have been flooded by extensive shallow seas

A

Late Cretacous, Ordovician, Early Carboniferous

22
Q

How is it suggested that epieric platforms were infact very dynamic environments?

A

Vast shallow-water carbonate factories responding to tectonics and progradation

23
Q

What type of platform is favoured in cooler waters and why?

A

Ramp platforms - Temperature favours hetrotrophic factories

24
Q

What is “Eustacy”?

A

Change in sea level

25
Q

What are the eight types of carbonate platforms as suggested by Bosence (2004)?

A

Fault-block, Salt diapir, Subsiding margin, Offshore bank, Volcanic pedestal, Thrust-top, Delta-top, Foreland margin

26
Q

Who is(are) the author(s) who proposed the idea of eight types of carbonate platforms?

A

Bosence (2004)

27
Q

What % of global hydrocarbon reserves reside in carbonate reservoirs?

A

> 50%

28
Q

What are the two reasons why carbonate reservoirs are difficult to predict?

A

Material which makes up the reservoirs has evolved through time, Carbonates more prone to diagenisis with burial

29
Q

Give an example where an entire petroleum system can reside in a single carbonate depositional system

A

Attached platform margin - steep downslope to deep-marine source rock, top is sealed by salt