Carbonate Mineralogy
Aragonite – high temperature mineral
Calcite – stable in sea water & near surface crust Low Magnesium Calcite
High Magnesium Calcite
Dolomite – stable in sea water & near surface
Carbonate rocks: > 50% of carbonate constituents
S.Cirilli-Sedimentary Petrology 3
S. Cirilli: Sedimentologia
Where?
S.Cirilli-Sedimentary Petrology
Depositional setting Type of deposit
Basin and slope Pelagic sediments. Turbidites and debris flows.
Platform margin Reefs and organic buildups. Sand shoals
Platform interior Epeiric sea, lagoon or bay, tidal flats
Terrestrial Dunes, lakes, cave deposits, solls, fanglomarate
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Skeletal & Non-Skeletal Settings in Bahamas S. Cirilli: Sedimentologia
Carbonate Components
S.Cirilli-Sedimentary Petrology 5
There are two main ways in which skeletal carbonates can be arranged. 1. insitu organisms building a more or less rigid framework (e.g. coral reefs, stromatolite)
2. Loose particles (allochemical grains) lithified after diagenesis Once these carbonate particles are produced and deposited other biological organisms, such as grasses and microbes, act as sediment traps and stabilizers. In this way the entire carbonate factory is controlled by biota and evolves with the biology of its own system.
Carbonate Components
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S. Cirilli: Sedimentologia
Lime Mud or
Micrite
Carbonate Components
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precipitation CaCO3 Periplatform
ooze
Lime mud in
Deep basin
Planktonic skeletal
Origin of mud in deep waters
S.C
irilli
-Sed
imen
tary
Pet
rolo
gy
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S. Cirilli: Sedimentologia S.Cirilli-Sedimentary Petrology
Muddy rock (hand sample)
Mud-supported texture (thin section under microscpoe) 1mm 11
Folk classification of carbonate rocks
Based on the presence of:
- micrite or sparite
- - kind of carbonate grains
Dunham classification of carbonate rocks:
• Texturally-based subdivision (loose particles): mudstone, wackestone,
packstone, grainstone, rudstone
• Organically bound framework during formation: boundstone
>10% grains > 2mm, grain or matrix supported (rudstone, floatstone)
Original components bound organically at deposition (framestone, bindstone,
bafflestone)
Classification of Carbonate rocks
Embry-Klovan classification of carbonate rock
S.Cirilli-Sedimentary Petrology
17
Folk classification
Based on the presence of:
- micrite or sparite
- - kind of carbonate grains
S.Cirilli-Sedimentary Petrology 18
Classificazione Rocce Carbonatiche di Dunham
• Texturally-based subdivision (loose particles): mudstone, wackestone, packstone, grainstone,
rudstone
• Organically bound framework during formation: boundstone S.Cirilli-Sedimentary Petrology 20
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