Carbonate platform Solubility of Carbonate mineral Types of Carbonate platform Controlling Parameters The great Bahamas platform Carbonate platform of western coast India

1. Controlling Parameters of Carbonate
Platform Environment
Department of Applied Geology
Dr. Harisingh Gour Vishwavidyalaya Sagar. MP
Under Guidance of:
Prof. D.C. Meshram
Department of Applied Geology
Presented by:
Rahul Vishwakarma
M.Tech 3rd Sem
Reg. no. Y22251046

2. Contents
• Introduction
• Solubility of Carbonate Minerals
• Types of Carbonate Platforms
i. Ramp Carbonate platform
ii. Rimmed shelf facies
iii. Epeiric Platform
iv. Isolated Platform
v. Drowned Platform
• Controlling Parameters
i. Climate
ii. Biogenic and salinity control
iii. Light and Depth Control
iv. Control of Nutrient supply
v. Tectonic and Sea level control
• The Great Bahamas Plarform
• Carbonate platform of western India
• Significance
• References

3. Introduction
• Areas of shallow marine carbonate
sedimentation are known as Carbonate
platforms.
• Modern day carbonates are not common but
they were very common in Triassic-
Cretaceous.
• The Great Bahamas Platform is a Example
of Modern day Carbonate Platform.
• Carbonates are mostly biogenic.
Figure 1: The Great Bahamas Platform
Source: Bahamabank.jpg –Wikipedia/ en.Wikipedia.org

4. • Most of Carbonate deposits are in-situ.
• Biological process can determine the
characteristics of the environment.
• Two main conditions for formation of
carbonate platform-
I. Isolation from clastic supply.
II. Shallow marine water.
• Deposition or carbonate platform
formation does not take above sea-level.
• Deposition may be faster than sea level
rise but will get cease after touching the sea
level. Fig2. Initiation, Growth and Drowning of Carbonate
platform.
Source: http//:google.images/Carbonate.platform

5. • Precipitation and dissolution of carbonates is controlled by the following
equations:
CaCO3 + CO2 + H2O Ca2+ + 2HCO3
-
H2O + CO2 H2CO3 ( slow hydration reaction)
H2CO3 H+ + HCO3
-
at interface between water and solid CaCO3, the equilibrium is
Ca+2 + CO3
-2 CaCO3

6. • The principle control on above reactions is the addition or removal of CO2 .
• Addition of CO2 results in release of more H+ and thereby, makes the water
column acidic.
• If CO2 is driven off, reversal of reaction encourage precipitation of carbonate.
• Presence of foreign ions interferes in the precipitation or growth carbonate
minerals aragonite or calcite and increase the solubility of carbonate minerals
many folds.

7. Solubility of Carbonate minerals
• Most stable carbonate mineral phase is
Low- Mg Calcite.
• The solubility of aragonite in distilled
water is same with High- Mg Calcite
having 12 mole % Mg.
• High- Mg Calcite with Mg mole % more
than 12% is more soluble than Aragonite.
• Dolomite is least stable among all
carbonates.
Fig 3: Carbonate Mineral Relative solubility
Source: http//:epgpathshala

8. Types of Carbonate Platforms
• Carbonate platform are classified on the basis of large – scale Geometry and slope.
• The study of carbonate platform type is important as they serves as rich
hydrocarbon source and reservoirs.
• Carbonate platform can change its type with respect to the change in Environment.
• Different platforms have different Geometry, facies, porosity and permeability.
• Different types of carbonate platforms are:
i. Carbonate ramp
ii. Carbonate Rimmed shelf
iii. Epeiric platform
iv. Isolated platform
v. Drowned Platform

9. 1. Carbonate Ramp
• A carbonate ramp is defined as a carbonate system with a very low
gradient/depositional slope (less than 10 ).
• Slope down deeper in water.
• No major break in Slope.
Fig 4: Figure showing different area of Carbonate platforms
Source: https://www.google.com/imgreswww.researchgate.net%2Fpublication%2

10. 2. Carbonate Rimmed shelf
• Grow along the shelf margin and flat topped platform is attached to the continent.
• There is a sharp change in slope.
• Reef is a vertically accreted organic build up and is wave like structure.
• Reefs are zone of maximum agitation and considered as important carbonate factory.
Fig 5. Carbonate rimmed shelf
Source: ScienceDirect.com

11. 3. Epeiric Carbonate Platform
• Almost of continental or sub-continental range (100-1000km).
• Developed during the global sea level when shallow shelf sea covered large
parts of continent.
• No modern example of Epeiric platform.
• Stratigraphic record indicates that such conditions have existed in the past
Particularly during the Jurassic and Creteceous.
Fig 5. Epeiric Carboante platform
Source: basin.earth.ncu.edu.tw

12. 4. Isolated Platforms
• Shallow water carbonates surrounded by deep- water carbonate.
• Have steeper side and slope towards deep water.
• Do not receive terrigenous clastic supply.
Fig 6. Isolated Carbonate platform
Source: ResearchGate

13. 5. Drowned Platform
• Any type of above platforms can be change into drowned carbonate platforms due to
rapid sea level rise.
• Deep water facies deposited over shallow water facies.
• If depth of platform is still within photic zone, then known as Incipiently drowned
platform.
Rapid rise in sea level
Platform below photic zone Fig 7. Drowned carbonate platform
Source:https://images.app.goo.gl/1SuUAK8PbWnAtqEo6

14. Controlling Parameters
• Carbonate depositional environment is a Dynamic system that responds to a
variety of parameters.
• Such parameters are Climate (humidity, temperature), Nutrient availability, Sea
level changes, Tectonic movement, Changes in Water and wind energy and
Biological determinants.
• Multitude of parameters are independent or superimposed upon each other.
• Due variety of controlling parameters study of study of architecture of carbonates
is still poorly understood.

15. • For each study area following parameters are investigated:
i. Tectonic setting : structural constrains, terrestrial influence
ii. Physical environmental parameters: wave energy and direction, water clarity, depth
of photic zone.
iii. Chemical parameters: nutrient supply, ocean chemistry, carbonate saturation state,
salinity.
iv. Biological parameters: richness of calcifying fauna, ecological reaction to physical
and chemical parameters.
v. Geometries of various facies belts: width, length, height, grain size, distribution,
dominant organisms, slope gradient.
• The understanding of the carbonate depositional environment and to close some of
the still existing gaps in understanding of the influence and interplay of individual
parameters.

16. a. Climate
• Climate of region decides the two major parameters that controls the solubility
and precipitation of the carbonates in that particular region: the temperature
and pressure.
• Temperature and pressure effects the solubility of CO2.
• With increase in temperature CO2 bubble off, escape from the water column
and help in precipitation of Carbonate.
• Decrease in temperature can hold more CO2 , in water column and trigger
carbonate dissolution.
• High pressure increase the solubility of CO2 in water column and increase the
solubility of carbonate.
• Precipitation of Carbonates is most favoured in tropical areas i.e between
300N and South of Equator where surface water temperature may reach nearly
300 C or more.

17. b. Biogenic and Salinity control
• Maximum marine biota proliferate between 30 to 40% salinity.
• High salinity is equally detrimental as low salinity for biotic Growth.
• Invertebrates disappear above 40% salinity.
• Calcareous algae can survive marginally above 40% salinity.
• Crinoids are very sensitive to salinity and commonly considered as marker of
salinity.
• Increase in salinity is caused by the relative increase in the particular ions like
Mg+2 .
• Calcite solubility is a function of its Mg content.
• Mg entry in carbonate structure causes distortion in the Carbonate structure
and increase its solubility in saline water.

18. c. Light and Depth control
• Most significant autogenic control is light
penetration.
• In ocean column light commonly penetrates
around 70m water depth ( max up to 100m)
which referred as Photic zone.
• Factors like siliciclastic input, upwelling can
cause in reduction in light penetration.
• In Euphotic zone sufficient amount of
photosynthesis takes place that uses the CO2
present in the water column and helps in the
carbonate precipitation.
• In tropical seas, carbonate production is
maximum within 15-20m water depth.
Fig 8. Depth wise variation in carbonate
sediment production, light penetration and
variation in sediment producing organisms

19. d. Control of Nutrient Supply
• Availability of nutrient is mandatory for biotic growth.
• Bioessential elements include P, N, Fe, Mo and Si which supplied to ocean by
continental weathering.
• Generally it is assumed that high nutrient supply increases the Carbonate production
but it is not so and mismatch is referred as Nutrient Paradox.
• High nutrient supply increases water turbidity, which in turn, reduces light
penetration and Carbonate production.
• Oligotrophic regions, where organisms consume all bioessential elements present
in water column and make the water column blue and clear and hence, are the
regions of maximum carbonate production.

20. e. Tectonic and Sea level control
• Carbonate platform develops in a whole range of geotectonic settings but
preferred along passive continental plate margin.
• The carbonate platform always respond to relative sea level fluctuations.
• Relative rise in sea level (Due to either tectonic subsidence or eustatic rise ) can
have the following types of effect on carbonate platforms:
i. Type A - Drowning ( Rise of sea level > carbonate sedimentation )
ii. Type B - Catch up/ survival of rim and patches
iii. Type C - Keep up/ upbuilding and outbuilding

21. • Relative fall in sea level ( either due to tectonic upliftment or drop in eustatic
sea level ) will expose shallow, flat carbonate platform and develop
widespread unconformity as drop in sea- level usually terminates carbonate
production at the shelf margins.
Fig 9. During rapid sea – level fall, delta encroaches from land onto carbonates and
coarse clastics may bypass a narrow shelf and onlap it to the seaward side, modified
after Kendall and Schlagar, 1981.

22. The Great Bahamas Carbonate Platform
• Consists of several isolated
carbonate platforms on a
passive continental margin.
• The Bahamas have a sub
tropical, humid, marine
climate.
• The annual average air
temperature is 250 C.
• Due to low latitude position
the Bahamas experience little
variation in daylight during
the year.
Fig 10. The Great Bahamas platform
Source: Research Gate

23. Carbonate platform of western India
• Carbonate platform lies at depths
between 60 and 90m on the outer
continental shelf off western India.
• Separated from the mainland by a
huge clastic Depocener – The
Dahanu depression.
• Petroleum occurs in the deeper
Miocene strata of the platform.
• Dolomite is the common component
in the platforms.
Fig 10. Carbonate
platform of western
India and Dahanu
depression
Source: Indian
Academy of Sciences

24. Significance
Controlling parameters of Carbonate platforms Envirnment are significant geological
features for several reasons:
• Biodiversity hotspots - Carbonate platforms often host diverse ecosystems due to
the favourable conditons.
• Sedimentary Record – They serve as excellent archives of Earth’s history
preserving sedimentary layers that offer into past environmental conditions.
• Economic Resources – Carbonate platforms are important reservoirs for oil, gas,
and Mineral resources.
• Carbonate Production – Carbonate platforms are significant contributors to the
global carbon cycle.
• Paleoclimate Reconstruction – By analizing carbonate platform sediments and
fossil assemblages reconstruction of past climates and environmental change
takes place.

25. References
• Tucker, Maurice E. and Wright, V. Paul (1990), Carbonate Sedimentology, Blackwell
Science Ltd. ISBN: 978-0-632-01472-93
• Kendall, C.G. St. C., Schlager, W., 1981. Carbonates and relative changes in sea level.
Marine Geology, 44, 181-212.
• Boggs. Sam Jr. (2011). Principles of Sedimentology and Stratigraphy, 5th Edn. Pearson
education, Inc, New Jersey. ISBN: 9780321643186, 0321643186
• Read, J.F., 1982. Carbonate platforms of passive (extensional) continental margins: types,
characteristics and evolution. Tectonophysics. 81, 195-212.
• H. Westphal et al. (eds.), Carbonate Depositional Systems: Assessing Dimensions and
Controlling Parameters, DOI 10.1007/978-90-481-9364-6_1,
• Kelly L. Bergman, Hildegard Westphal, Xavier Janson, Anthony Poiriez, and Gregor P.
Eberli, Controlling Parameters on Facies Geometries of the Bahamas, an Isolated
Carbonate Platform Environment.
• V Purnachandra Rao and P Gopinathan, Late Quaternary sediments on the carbonate
platform off western India: Analogues of ancient platform carbonates, J. Earth Syst. Sci.
(2019) 128:80,https://doi.org/10.1007/s12040-019-1112-y

26. Thank You!