Carbonate stratigraphy and dynamics

Question 1

What causes the vertical superposition of facies in time?

Answer 1

Lateral migration of facies belts (Walther’s Law)

Question 2

What is eustatic (worldwide) sea level change controlled on long time scales by?

Answer 2

Volume of water in oceans (related to glacial ice volumes) and volume of ocean basins (related to spreading rates and plate tectonics)

Question 3

How do carbonates respond to sea level fall?

Answer 3

Karstification of limestones

Question 4

Describe peritidal facies

Answer 4

Stacked vertical succession of increasingly shallow water facies

Question 5

What are shallowing-up succession evidence of?

Answer 5

Seaward facies migration
Controls may be related to sedimentary processes and/or eustatic sea level fluctuations

Question 6

What can carbonates be used to deduce?

Answer 6

Evolution, climates, environments, ocean chemistry, reef ecology, clastic input

Question 7

Why does uniformitarianism not strictly apply to carbonates?

Answer 7

Changes in biota through time by evolution

Question 8

How does the rate of sea floor spreading influence carbonate production?

Answer 8

Influences the abundance of atm CO2 and therefore CO2 precipitation/dissolution

Question 9

How can local/regional tectonism influence carbonate production?

Answer 9

Can control platform geometry

Question 10

How can plate tectonics influence carbonate production?

Answer 10

Controls distribution of clastic sediment, influencing hinterland topography and river drainage

Question 11

Describe the ocean chemistry that is favourable for precipitation of high magnesium calcite and aragonite

Answer 11

High Mg:Ca (>5)
Low pCO2

Question 12

Describe greenhouse climates

Answer 12

High spreading rates and dispersed continents
High sea level
Low latitudinal temp gradient (warm at poles)
No continental ice

Question 13

Describe the ocean chemistry of greenhouse climates

Answer 13

Increase pCO2 by production of CO2 from processes at subduction zones and MOR
Lower Mg:Ca via hydrothermal basalts at MOR
Dominantly calcite seas

Question 14

Describe icehouse climate

Answer 14

Low spreading rates and assembled continents
Low sea level
High latitudinal temperature gradient (cold at poles)
Continental ice sheets at the poles

Question 15

Describe the ocean chemistry of icehouse climates

Answer 15

Decreased pCO2 through increased photosynthesis
Increased Mg:Ca, increased Mg supply from continental weathering, removal of Ca via evaporite precipitation
Dominantly aragonite seas