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EART23202 Interpreting the stratigraphic record > Carbonate platforms > Flashcards

Carbonate platforms Flashcards

1
Q

Give three chemical controls on carbonate deposition

A

Nutrient supply, salinity, oxygen

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2
Q

Give four physical controls on carbonate deposition

A

Light, turbulence, temperature, nature of substrate (hard/soft)

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3
Q

What is carbonate depostion primarily dominated by?

A

Biological acitivity

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4
Q

What are the three primary energy sources for carbonate precipitation?

A

Carbonate supersaturation, light, organic matter

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5
Q

Describe the transport of carbonate grains

A

Usually not transported any great distance

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6
Q

What is produced by carbonate supersaturation?

A

Non-skeletal grains, muds, microbes (ooids, stromatolites)

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7
Q

What is carbonate supersaturation controlled by?

A

High temperatures, high salinity, oceanic restriction

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8
Q

Describe whitings

A

Precipitation of aragonite in regions of elevated salinity

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9
Q

What factors control light availability?

A

Temperature, depth, transparency

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10
Q

What carbonate producers are allowed by light?

A

Photozoan (corals, green algae), symbiotic foraminifera, and red algae

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11
Q

What is the main controlling parameter of organic matter?

A

Food supply

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12
Q

What carbonate producer is energised by organic matter

A

Heterozoans

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13
Q

Give three examples of in situ carbonate build up by growth of skeletons of autotrophic organisms

A

Corals, algae, stromatoporoids

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14
Q

Give three sources of in situ carbon growth by heterotrophic organisms

A

Bryozoa, crinoids, bivalves

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15
Q

What leaves to high volumes of carbonate mud?

A

Growth of benthic algae

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16
Q

Where does 80% of modern carbonate depostion come from?

A

Deposited as carbonate ooze, derived from coccoliths and planktonic forams
Driven by photosynthesis by autotrophic organisms

17
Q

Describe the role of benthic organisms in carbonate production

A

Deposit carbonates in shallow to deep marine environments
Dominated by heterotrophic organisms

18
Q

How do platforms form?

A

In situ deposition of carbon

19
Q

What are the three modes of production of carbonate platforms?

A

Tropical topmost water, cool-water-controlled precipitates, mud mound micrite

20
Q

What are the four classification of carbonate platform?

A

Ramp, rimmed, epeieric, isolated

21
Q

Where are the main settings for carbonate production?

A

Shallowest areas with waves and currents and the most photic energy

22
Q

Describe a rimmed shelf

A

Shelf margin break, defined by reef growth or carbonate sandbodies
Zone of high organic productivity
e.g. Bahamas platform

23
Q

Describe the shelf margin of a rimmed shelf

A

Ocean-facing, high energy, and turbulent

24
Q

Why do carbonate sheleves have steep angles at the edge?

A

Competitive growth of coral

25
Q

Describe a carbonate ramp

A

Shallow-dipping carbonate platforms
Subdivided on the basis of the influence of waves/storms on sedimentation

26
Q

Describe the inner section of a carbonate ramp

A

This area is high energy and wave agitated, sand shoals can develop, offering landward protection from wave/storm energy

27
Q

Describe the mid and outer ramp of a carbonate ramp

A

Sedimentation is frequently storm influenced in the mid ramp and infrequently storm-reworked in the outer ramp

28
Q

Describe the basin of a carbonate ramp

A

Very low energy with negligible storm influence

29
Q

Describe epeiric carbonate platforms

A

Deposited in epi-continental seas, no analogue today
Dominated by shallow water, storm-influenced, shallow subtidal-intertidal sedimentation

30
Q

What conditions favour carbonate production?

A

Warm water, elevated salinity, protection from terrigenous influx

31
Q

Describe high-energy platform margins

A

Reef growth (in situ carbonate build up)
Reworking by storms, currents (producing rubble)
Export to basin by gravity processes

32
Q

Describe where oolite carbonate sand shoals are found

A

High energy locations
Depositional processes include in situ precipitation of ooids and reworking by tidal currents/storms/waves

33
Q

Describe the back interior/lagoon

A

Low-energy
Depositional processes include accumulation of faecal pellets (worms/gastropods), chemical precipitation (e.g. whitings), disintegration of algae (mud)

34
Q

Describe tidal flats

A

Land-attached areas
Depositional processes include reworking by tidal currents and waves and the movement of subtidal sediement onto tidal flat/into lagoon by storms

EART23202 Interpreting the stratigraphic record (11 decks)

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