Batuan Sedimen Karbonat.pdf

Batuan Karbonat

Formation of carbonates 

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Shallow Marine –Late Proterozoic to Modern Deep Marine – Rare in Ancient & commoner in Modern Cave Travertine and Spring Tufa – both Ancient & Modern Lakes – Ancient to Modern

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SHELF CARBONATE PLATFORM REEFAL SEDIMENTATION

MARGIN

RESTRICTED

OPEN MARINE

SHELF

SLOPE

BASIN

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Controls on Carbonate Formation 

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Temperature (climate) -Tropics & temperate regions favor carbonate production: true of ancient too! Light – Photosynthesis drives carbonate production Pressure – “CCD (calcite compensation depth)” dissolution increases with depth Agitation of waves - Oxygen source & remove CO2 Organic activity - CaCO3 factories nutrient deserts

Patch Reefs

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Patch Reefs

Sand Shoal Apron Joulters Cay - Bahamas

Kendall Photo

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Oo id Sa nd Ri pp les

Heron Island Reef

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Base of Carbonate Slope - Bahamas

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Mineralogi  

Aragonite – high temperature mineral Calcite – stable in sea water & near surface crust  

Low Magnesium Calcite High Magnesium Calcite  

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Imperforate foraminifera Echinoidea

Dolomite – stable in sea water & near surface

Komponen batuan karbonat 1. Fragments: - skeletal - non skeletal - carbonate - non carbonate 2. Mikrit (micrite – microcrystalline calcite) 3. Semen 4. Porositas

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Fragments – carbonate, non skeletal   

Ooids Grapestones and other intraclasts Pellets

Ooids

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Grapestones & intraclasts

Intraclast

Pellets

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Pelloids

Fragments – skeletal 

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Calcite, e.g. brachiopods, bryozoans, ostracodes, echinoderms, foraminifera, red algae Aragonite, e.g. corals, orals, stromatoporoids, stromatoporoids, most molluscs, green algae Silica, e.g. sponge spicules & radiolarians

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Fragments – non carbonate   

Detrital minerals: quartz, feldspar, etc Rock fragments Non-carbonate fossils

Lime Mud or Micrite

Mechanical breakdown

Bioerrosion

Chemical precipitation

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Semen  

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Crust or rims coat grains Syntaxial overgrowth – optical continuity with skeletal fabric Blocky equant - final void fill

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Porositas 1. Primer - Interclast - Intraclast 2. Sekunder - Dissolution - Fractures

C. G. St. C. Kendall

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Moldic porosity

Channel porosity

1.02 mm

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Vug porosity

Klasifikasi

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Klasifikasi

Embry& Klovan (1971) Limestone Classification

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Lithifikasi / Diagenesis 1. 2. 3. 4. 5. 6. 7. 8. 9.

Kompaksi Pressure solution Sementasi Dissolution Dolomitisisasi De-dolomitisasi Fracturing Neomorphism etc

DIAGENESIS – CEMENTATION

0.5 mm

0.5 mm

PPL

PPL

Non-ferroan calcite spar

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DIAGENESIS – MECHANICAL COMPACTION

0.5 mm

PPL

0.25 mm

PPL

Compaction due to burial diagenesis

DIAGENESIS - DISSOLUTION

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