Carbonate Rocks

Carbonate Rocks

• Limestone and dolomites• They are called carbonate rocks because

they contain large amounts of carbonate(CO3).

• Carbonate rocks are the most abundant non-terrigenous sedimentary rock.

Carbonate Rocks• They form chemically and biochemically.• Dissolved ions carried from source to

depositional site in solution eventuallyprecipitate and form solid minerals.

• Organism have a role in their formation. Theyextract dissolved components from sea-waterto manufacture shells or skeletons that later areincorporated in the sedimentary record. Theycan also modify the geochemical settingenough to cause mineral precipitation.

Carbonate Geochemistry

Controls on Carbonate Deposition• Temperature- rising the temperature results in

limestone deposition.• Pressure- reducing the pressure results in

limestone deposition (gas escape).• Degree of agitation- Breaking waves results in

limestone deposition (gas escape).• Organic activity- Plants and animals either

directly precipitate calcium carbonates ormodify the geochemical environment enoughfor precipitation to occur.

• Light- because photosynthetic organismextract CO2 it results in carbonateprecipitation (water shallow enough less than20 meters).

• CCD

Controls on CarbonateDeposition

Limestone classification

• Folk (1959, 1962)• Dunham (1962) and Embry and Klovan

(1972) Modification of Dunhamclassification

Folk (1959, 1962)

Textural maturity classificationof limestone proposed by Folk

Classification of limestoneproposed by Dunham (1962)

Embry and Klovan (1972) Modificationof Dunham classification