Carbonate platforms

Question 1

Give three chemical controls on carbonate deposition

Answer 1

Nutrient supply, salinity, oxygen

Question 2

Give four physical controls on carbonate deposition

Answer 2

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

Question 3

What is carbonate depostion primarily dominated by?

Answer 3

Biological acitivity

Question 4

What are the three primary energy sources for carbonate precipitation?

Answer 4

Carbonate supersaturation, light, organic matter

Question 5

Describe the transport of carbonate grains

Answer 5

Usually not transported any great distance

Question 6

What is produced by carbonate supersaturation?

Answer 6

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

Question 7

What is carbonate supersaturation controlled by?

Answer 7

High temperatures, high salinity, oceanic restriction

Question 8

Describe whitings

Answer 8

Precipitation of aragonite in regions of elevated salinity

Question 9

What factors control light availability?

Answer 9

Temperature, depth, transparency

Question 10

What carbonate producers are allowed by light?

Answer 10

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

Question 11

What is the main controlling parameter of organic matter?

Answer 11

Food supply

Question 12

What carbonate producer is energised by organic matter

Answer 12

Heterozoans

Question 13

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

Answer 13

Corals, algae, stromatoporoids

Question 14

Give three sources of in situ carbon growth by heterotrophic organisms

Answer 14

Bryozoa, crinoids, bivalves

Question 15

What leaves to high volumes of carbonate mud?

Answer 15

Growth of benthic algae

Question 16

Where does 80% of modern carbonate depostion come from?

Answer 16

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

Question 17

Describe the role of benthic organisms in carbonate production

Answer 17

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

Question 18

How do platforms form?

Answer 18

In situ deposition of carbon

Question 19

What are the three modes of production of carbonate platforms?

Answer 19

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

Question 20

What are the four classification of carbonate platform?

Answer 20

Ramp, rimmed, epeieric, isolated

Question 21

Where are the main settings for carbonate production?

Answer 21

Shallowest areas with waves and currents and the most photic energy

Question 22

Describe a rimmed shelf

Answer 22

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

Question 23

Describe the shelf margin of a rimmed shelf

Answer 23

Ocean-facing, high energy, and turbulent

Question 24

Why do carbonate sheleves have steep angles at the edge?

Answer 24

Competitive growth of coral

Question 25

Describe a carbonate ramp

Answer 25

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

Question 26

Describe the inner section of a carbonate ramp

Answer 26

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

Question 27

Describe the mid and outer ramp of a carbonate ramp

Answer 27

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

Question 28

Describe the basin of a carbonate ramp

Answer 28

Very low energy with negligible storm influence

Question 29

Describe epeiric carbonate platforms

Answer 29

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

Question 30

What conditions favour carbonate production?

Answer 30

Warm water, elevated salinity, protection from terrigenous influx

Question 31

Describe high-energy platform margins

Answer 31

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

Question 32

Describe where oolite carbonate sand shoals are found

Answer 32

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

Question 33

Describe the back interior/lagoon

Answer 33

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

Question 34

Describe tidal flats

Answer 34

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