Carbonate Rock Diagenesis

Burial

1. Compaction

Condensed benthic foraminifera grainstone with Lepidocyclina (centre right), Nummulites (centre left), Miogypsinoides (upper and lower left) and bryozoans (lower right corner) from inner to middle ramp of early Oligocene age with mechanical compaction features due to burial diagenesis: a) broken skeletal grains, b) compenetrated concave-convex grain contact, c) drusy mosaic of blocky sparite (left corner).

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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2. Compaction

Condensed crinoidal packstone with carbonate mud and argillaceous matrix sutured at grain contacts from a Mississippian mound flank facies in the middle ramp.

Mississippian, New Mexico, USA

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3. Compaction

Condensed skeletal packstone with rotalids, echinoderms, Lepidocyclina and coralline red algae rhodoids from Oligocene middle ramp facies with concave-convex and sutured grain contacts due to burial compaction.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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4. Compaction

Condensed skeletal packstone with Nummulites, rotalids, echinoderms, Lepidocyclina, bryozoans and coralline red algae rhodoids from Oligocene middle ramp facies with concave-convex and sutured grain contacts due to burial compaction.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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5. Compaction

Fitted skeletal grainstone with Nummulites, Lepidocyclina and rotalids with broken foraminifera (centre right) and sutured grain contacts due to burial compaction. Facies from lower Oligocene inner ramp.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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6. Compaction

Skeletal packstone with miliolids (centre right), alveolinids (centre left), rotalids (left corner), echinoderms and grains with micrite envelopes from a lagoon of Eocene age. Grain contacts are concave-convex and the alveolinid has been deformed due to partial dissolution.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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7. Stylolite

Stained (Alizarin red, K ferricyanide) thin section of an ooidal grainstone with thin rims of possibly early marine cement (pink), followed by a mosaic of blocky ferroan calcite (blue) of burial origin. The deposit shows a well-developed stylolite crossing in diagonal the thin section. The dark material (Fe oxides, clay minerals) within the stylolite represents the insoluble residue of the pressure solution process.

Pennsylvanian, Asturias, N Spain, cf. Bahamonde et al. (2015, 2017)

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8. Burial Cement

Stained (Alizarin red, K ferricyanide) thin section of an ooidal grainstone with a fracture breaking up the large ooid in the centre. Interparticle space and fracture have been filled by mostly blue-stained ferroan blocky calcite precipitated in burial (reducing) diagenetic environment.

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9. Burial Cement

Stained (Alizarin red, K ferricyanide) thin section of an ooidal grainstone cemented by large crystals of ferroan calcite (blue) with poikilotopic fabric precipitated in burial (reducing) environment. Cementation follows mechanical compaction.

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10. Burial Cement

Stained (Alizarin red, K ferricyanide) thin section of an ooidal grainstone showing compaction related concave-convex grain contacts followed by burial cement (blue stained ferroan calcite) from a Visean inner ramp facies belt.

Mississippian, South Wales, UK

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11. Burial Cement

Stained (Alizarin red, K ferricyanide) thin section of an ooidal grainstone showing compaction related concave-convex grain contacts and burial cement (blue stained ferroan calcite) from a Visean inner ramp facies belt. The crinoid ossicle in the centre exhibits the growth of syntaxial calcite (cement grown in optical continuity with the crystalline axis of the echinoderm fragment).

Mississippian, South Wales, UK

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12. Burial Cement

Stained (Alizarin red, K ferricyanide) thin section of a skeletal coated grain (ooids and cortoids) grainstone with blue-stained ferroan calcite. Some of the coated grains have quartz detrital grains as nuclei. The deposit is crossed by a fracture filled by burial ferroan calcite.

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13. Burial Cement

Stained (Alizarin red, K ferricyanide) thin section of a skeletal (gastropods, brachiopods, bivalves) coated grain (ooids and cortoids) grainstone showing a mosaic of blue-stained blocky ferroan calcite. Some of the coated grains have quartz detrital grains as nuclei.

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14. Burial Cement

Stained (Alizarin red, K ferricyanide) thin section of an ooidal grainstone cemented by a thin (a few microns) isopachous rim of bladed cement (phreatic marine origin?) and equant blocky sparite of possible burial origin (blue-purple staining).

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15. Burial Cement

Stained (Alizarin red, K ferricyanide) thin section of an ooidal grainstone with large crystals of poikilotopic (growing beyond the grain boundaries and including more grains within the same crystal) ferroan calcite common in burial diagenetic environment.

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16. Burial cement

Stained (Alizarin red, K ferricyanide) thin section of an ooidal (micritised and broken) skeletal grainstone that was compacted (concave-convex grain contact) previous to cementation by burial ferroan calcite (blue). On the left side, some non-ferroan (pink) syntaxial and blocky calcite had been precipitated before deep burial and there are no evidences of chemical-mechanical compaction.

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17. Burial cement

Stained (Alizarin red, K ferricyanide) thin section of an ooidal (partly micritised ooids) grainstone likely cemented in the meteoric phreatic zone (pink rims of non-ferroan equant calcite) and in the burial diagenetic environment (blue equant blocky sparite).

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18. Burial Cement

Stained (Alizarin red, K ferricyanide) thin section of a skeletal ooidal grainstone showing a gastropod mould in the centre filled by zoned calcite crystals. The staining puts in evidence the successive phases of growth of the crystals and the alternation of redox conditions of the precipitating fluid between reducing (ferroan calcite, blue) and oxidising (non ferroan calcite, pink).

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19. Burial Cement

Stained (Alizarin red, K ferricyanide) thin section of a skeletal ooidal grainstone showing a gastropod mould in the centre filled by zoned calcite crystals. The staining highlights the successive phases of growth of the crystals and the alternation of redox conditions of the precipitating fluid between reducing (ferroan calcite, blue) and oxidising (non ferroan calcite, pink).

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20. Drusy Cement

Skeletal and cortoid (grains with micrite envelopes) grainstone showing in the centre the micrite envelope lining a dissolved mollusc shell. The blocky calcite spar exhibits locally a drusy fabric with increasing crystal size towards the centre of the pore.

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21. Drusy Cement

Skeletal packstone with a gastropod mould filled by drusy sparite with crystal size increasing towards the pore centre precipitated during burial diagenesis.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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22. Drusy Cement

Skeletal, peloidal and cortoid (grains with micrite envelopes) grainstone showing in the centre the micrite envelope lining a dissolved bioclast. The mosaic of calcite spar exhibits a drusy fabric with increasing crystal size towards the centre of the biomold.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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23. Syntaxial Cement

Coated grain and superficial ooid grainstone with two echinoderm plates (centre right) showing syntaxial growth of calcite cement. Syntaxial cement can form in phreatic meteoric, burial and possibly in marine environments.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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24. Syntaxial Cement

Previous image in crossed polarisers. Coated grain and superficial ooid grainstone with two echinoderm plates in the centre right showing syntaxial growth of calcite cement. The image shows the simultaneous extinction of the echinoid plate and the syntaxial cement.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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25. Syntaxial Cement

Previous image in crossed polarisers. Coated grain and superficial ooid grainstone with two echinoderm plates in the centre right showing syntaxial growth of calcite cement. The image shows the simultaneous extinction of the echinoid plate and the syntaxial cement.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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26. Silicification

Coated grain skeletal packstone-grainstone with quartz grains (centre left) showing in the centre an echinoderm fragment with syntaxial cement and silicification.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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27. Silicification

Skeletal (foraminifera) grainstone with silicification: white patches in parallel polarised light.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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28. Silicification

Previous image viewed in crossed polarised light showing the skeletal (foraminifera) grainstone with silicification: patches with grey-white interference colours of fibrous chalcedony.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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29. Silicification

Image viewed in crossed polarisers of a crinoidal grainstone with dominant syntaxial cement and silicification processes on some ossicles.

Mississippian, New Mexico, USA

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30. Silicification

Example of silica replacement by megaquartz of a rudist shell (calcite mineralogy, pink because stained with Alizarin red) viewed in parallel polarized light.

Upper Cretaceous (Turonian), Miskar Field, offshore Tunisia

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31. Silicification

Previous image in cross polarisers, example of silica replacement by megaquartz of a rudist shell (calcite mineralogy, pink because stained with Alizarin red).

Upper Cretaceous (Turonian), Miskar Field, offshore Tunisia

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32. Mechanical compaction

Skeletal and coated grain grainstone with isopachous rims of marine fibrous cement that has been broken up by mechanical compaction. Field of view appoximately 2 mm wide.

Carboniferous, Karachaganak Field, Kazakhstan

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33. Concave-convex grain contacts

Coated grain grainstone with evidence of chemical compaction with pressure solution of carbonate grains against more resistant quartz grains and concave-convex grain contacts.

Jurassic, Oxfordshire, UK

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34. Fitted fabric

Open-packed, well-cemented oolitic grainstone with early marine cement overlain by a skeletal packstone with fitted fabric because of compaction in absence of previous cementation (transgressive skeletal intraclast deposit). Field of view approximately 4.8 mm wide.

Mississippian, Gilwern Oolite, Llanelly Fm., South Wales, UK

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35. Stylolite

Stylolite marked by insoluble bitumen following pressure solution/chemical compaction in Nummulites-rich packstone.

Eocene, El Garia Formation, Hasdrubal Field, offshore Tunisia

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36. Stylolite

Stylolite in ooidal grainstone following pressure solution/chemical compaction.

Jurassic, southern England, UK

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37. Fitted fabric

Eocene Nummulites-dominated fitted fabric grainstone where grain contacts are fully sutured due to compaction and pressure solution.

Eocene, El Garia Formation, Hasdrubal Field, offshore Tunisia

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38. Syntaxial cement

Echinoderm grainstone showing syntaxial cement.

Carboniferous, Karachaganak Field, Kazakhstan

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39. Authigenic quartz

Image in crossed polarisers of peloidal wackestone with formation of authigenic quartz crystals in a Carboniferous mud mound facies.

Mississippian, Waulsortian mounds, Ireland

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40. Silicification

Image in plane polarised light of a calci-mudstone with diffuse silicification of the micrite.

Permian, Capitan Reef, New Mexico, USA

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41. Silicification

Previous image in crossed polarizers showing a calci-mudstone with diffuse silicification of the micrite.

Permian, Capitan Reef, New Mexico, USA

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42. Neomorphic microsparite

Neomorphism of original micrite recrystallized in microsparite in a skeletal grainstone/packstone with Orbitolinid foraminifer (Lower Cretaceous).

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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43. Neomorphic microsparite

Previous image in crossed polarizers with neomorphic microsparite due to recrystallization of micrite in a skeletal grainstone/packstone with Orbitolinid foraminifer (Lower Cretaceous).

Thin section provided by T. Geel, Vrije Universiteit, Amsterdam

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44. Blocky sparite

Blocky mosaic of equant sparite of burial origin following a scalenohedral calcite cement rim.

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45. Drusy fabric

Burial calcite spar can display drusy fabric with increase of crystal size towards the centre of the pore.

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46. Drusy fabric

Calcite cement in a coral with a drusy fabric where the crystal size increases towards the pore centre.

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47. Drusy fabric

Burial calcite spar can display drusy fabric with increase of crystal size towards the centre of the pore.

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48. Etched cement

Etched late burial cement and intercrystalline porosity.

Upper Cretaceous, Miskar Field, offshore Tunisia

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49. Burial corrosion

Burial corrosion is a type of limestone selective dissolution occurring in the burial diagenetic environment. Extensive selective dissolution has taken place after cementation (sparite filling miliolid intraparticle porosity) and after pressure solution with the preferential removal of walls of miliolid foraminifera.

Bassein Limestone, Eocene, Mukta Field, Bombay High, offshore India

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50. Burial corrosion

Corroded cement from mouldic pores in rudist grainstone. Field of view approximately 0.5 mm wide.

Cretaceous, Mishrif Formation, Dubai, UAE

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51. Burial corrosion

Extensive selective dissolution has taken place after cementation. In this image corroded sparite dissolution took place after pressure solution. The clay mineral dickite (green) was precipitated in some of the dissolution pores.

Bassein Limestone, Eocene, Mukta Field, Bombay High, offshore India

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52. Burial corrosion

Some calcite-filled veins and micrite were affected by burial dissolution taking place after pressure solution.

Bassein Limestone, Eocene, Mukta Field, Bombay High, offshore India

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53. Burial corrosion

Extensive selective dissolution of micrite has taken place after cementation and pressure solution.

Bassein Limestone, Eocene, Mukta Field, Bombay High, offshore India

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54. Burial corrosion

Burial corrosion after cementation has almost completely removed the foraminifera grains and has left a framework of relict cements.

Bassein Limestone, Eocene, Mukta Field, Bombay High, offshore India

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55. Dickite

View in parallel (left) and cross (right) polarized light of dickite (clay mineral; high temperature kaolinite) cement filling secondary pore space formed due to partial dissolution of the burial zoned cements (stained).

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56. Saddle dolomite

Example of burial corrosion on saddle dolomite cement formed in fracture. Dissolution took place late in the burial diagenesis, probably at depths of > 2 km.

Eocene, Mukta Field, Bombay High, offshore India

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57. Saddle dolomite

Late burial diagenesis with saddle dolomite in a fracture that includes pyrite and dickite.

Eocene, Mukta Field, Bombay High, offshore India

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58. Dickite

Corroded saddle dolomite and dickite formed during burial diagenesis in a fracture. Saddle dolomite has undergone corrosion followed by dickite precipitation (thin section stained with Alizarin red).

Eocene, Mukta Field, Bombay High, offshore India

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59. Anhydrite

Replacive anhydrite in Cretaceous skeletal packstone (stained with Alizarin red).

Upper Cretaceous (Turonian), Miskar Field, offshore Tunisia

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60. Prismatic calcite

Prismatic calcite in a fracture and silicification of bioclasts in a micrite coated grain and skeletal packstone.

Thin section provided by T. Geel, Vrije Universiteit, Amsterdam

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61. Silicification

Previous image in cross-polarized light with prismatic calcite in a fracture and silicification on bioclasts.

Thin section provided by T. Geel, Vrije Universiteit, Amsterdam

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62. Dickite

Dickite cement filling pore space after partial dissolution of the burial zoned cements. Note etched cement crystal edges. Image in plane (left) and crossed (right) polarizers.

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concave-convex grain contact

drusy sparite

sutured grain contact

sutured grain contact

concave-convex grain contact

sutured grain contacts

deformed alveolinid

stylolite

blocky ferroan calcite

ferroan calcite spar

poikilotopic ferroan calcite spar

ferroan calcite spar

ferroan calcite spar

non ferroan syntaxial cement

ferroan calcite spar in fracture

ferroan calcite

coated quartz grain

pink isopachous rims

equant blocky sparite

poikilotopic ferroan calcite

concave-convex grain contact

ferroan calcite

isopachous rims of equant non ferroan calcite

ferroan calcite cement

drusy calcite

drusy calcite

drusy calcite

syntaxial cement

syntaxial cement

syntaxial cement

silicification

silicification

chalcedony

silicification

rudist shell

quartz

rudist shell

quartz

broken isopachous fibrous cement

interparticle porosity

concave-convex grain contacts

coated grain

fitted fabric

well-cemented ooidal grainstone

stylolite

Nummulites

stylolite

ooid

sutured grain contact

intraparticle porosity in Nummulites

interparticle porosity

syntaxial cement

authigenic quartz

silicification

silicification

Orbitolinid foraminifer

neomorphic microsparite

neomorphic microsparite

Orbitolinid foraminifer

neomorphic microsparite

echinoid spine

blocky equant sparite

scalenohedral cement

drusy fabric

coral skeleton

drusy fabric

drusy fabric

etched burial cement

late corrosion porosity

miliolid foraminifer

burial corrosion dissolution

corroded calcite cement

secondary porosity

dickite

corroded sparite

calcite-filled veins

burial corrosion

relict cement

burial corrosion porosity

dickite

calcite spar

saddle dolomite

porosity

saddle dolomite

pyrite

dickite

saddle dolomite

calcite

anydrite

silicification

prismatic calcite in fracture

silicification

prismatic calcite in fracture

dickite

etched calcite cement

Burial

CLOSE

concave-convex grain contact

drusy sparite

sutured grain contact

sutured grain contact

concave-convex grain contact

sutured grain contacts

deformed alveolinid

stylolite

blocky ferroan calcite

ferroan calcite spar

poikilotopic ferroan calcite spar

ferroan calcite spar

ferroan calcite spar

non ferroan syntaxial cement

ferroan calcite spar in fracture

ferroan calcite

coated quartz grain

pink isopachous rims

equant blocky sparite

poikilotopic ferroan calcite

concave-convex grain contact

ferroan calcite

isopachous rims of equant non ferroan calcite

ferroan calcite cement

drusy calcite

drusy calcite

drusy calcite

syntaxial cement

syntaxial cement

syntaxial cement

silicification

silicification

chalcedony

silicification

rudist shell

quartz

rudist shell

quartz

broken isopachous fibrous cement

interparticle porosity

concave-convex grain contacts

coated grain

fitted fabric

well-cemented ooidal grainstone

stylolite

Nummulites

stylolite

ooid

sutured grain contact

intraparticle porosity in Nummulites

interparticle porosity

syntaxial cement

authigenic quartz

silicification

silicification

Orbitolinid foraminifer

neomorphic microsparite

neomorphic microsparite

Orbitolinid foraminifer

neomorphic microsparite

echinoid spine

blocky equant sparite

scalenohedral cement

drusy fabric

coral skeleton

drusy fabric

drusy fabric

etched burial cement

late corrosion porosity

miliolid foraminifer

burial corrosion dissolution

corroded calcite cement

secondary porosity

dickite

corroded sparite

calcite-filled veins

burial corrosion

relict cement

burial corrosion porosity

dickite

calcite spar

saddle dolomite

porosity

saddle dolomite

pyrite

dickite

saddle dolomite

calcite

anydrite

silicification

prismatic calcite in fracture

silicification

prismatic calcite in fracture

dickite

etched calcite cement