Carbonate Rock Diagenesis

Marine

1. Fibrous Cement

Ooidal grainstone with rims of acicular (aragonitic) marine cement viewed in parallel polarised light (Recent, Bahamas).

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

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2. Fibrous Cement

Ooidal grainstone with rims of acicular (aragonitic) marine cement viewed in cross polarised light (Recent, Bahamas).

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

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3. Fibrous Cement

Enlarged view of previous image of ooidal grainstone with rims of acicular (aragonitic) marine cement viewed in crossed polarisers (Recent, Bahamas).

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

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4. Fibrous Cement

Enlarged view of previous image of ooidal grainstone with rims of acicular (aragonitic) marine cement viewed in crossed polarised light (Recent, Bahamas).

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

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5. Fibrous Cement

Skeletal grainstone with isopachous rims of fibrous marine cement viewed in parallel polarised light. In the top left corner the benthic foraminifer Archaias.

Recent, Bahamas

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6. Fibrous Cement

Ooidal and micrite-coated grain grainstone with an almost isopachous rim of turbid, impurity-rich bladed cement followed by mms long rims of radial fibrous cement.

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7. Isopachous Cement

Stained thin section (Alizarin red + K Ferricyanide) showing an ooidal and aggregate-micrite coated grain grainstone with grains surrounded by a thin isopachous rim of calcite cement of possibly marine origin (pink). Remaining pore space has been filled by Fe calcite (blue with K Ferricyanide because of burial reducing conditions) in the burial diagenetic environment.

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

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8. Botryoidal aragonite

Cementstone from Permian reef facies showing irregular mosaic of calcite spar neomorphic on botryoids of former aragonite crystals. Botryoidal aragonite was a typical cement of upper Palaeozoic and Triassic reefs. Botryoids (hemispherical shape) have the outer rounded margin lined by micrite crust and clots.

Permian, New Mexico, USA

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9. Botryoidal aragonite

Cementstone from Permian reef facies showing irregular mosaic of calcite spar neomorphic on botryoids of former aragonite crystals as in previous image viewed in cross polarised light.

Permian, New Mexico, USA

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10. Botryoidal aragonite

Cementstone from Permian reef facies showing irregular mosaics of calcite spar neomorphic on botryoids of former aragonite crystals. Botryoids (hemispherical shape) have the outer rounded margin lined by micrite crusts, clots and peloids of possible biologically induced/influenced (microbial) origin.

Permian, New Mexico, USA

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11. Radiaxial Fibrous Cement

Primary cavity in Permian reef facies lined by 1-2 mm thick crystals of radiaxial fibrous calcite cement with polygonal contacts (indicative of fast cement growth).

Permian, New Mexico, USA

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12. Radiaxial Fibrous Cement

Previous image of primary cavity in Permian reef facies lined by 1-2 mm thick crystals of radiaxial fibrous calcite viewed in crossed polarised light.

Permian, New Mexico, USA

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13. Radial Fibrous Cement

Primary cavity in Permian reef facies (to notice that the cavity is supported by microbial peloidal micrite crusts) lined by 1-2 mm thick crystals of radial fibrous cement. The remaining pore space in the centre is filled by mosaic of equant sparite.

Permian, New Mexico, USA

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14. Radial Fibrous Cement

View in crossed polarised light of previous image. Primary cavity in Permian reef facies (to notice that the cavity is supported by automicrite of possible microbial origin) lined by 1-2 mm thick crystals of radial fibrous calcite. The remaining pore space in the centre is filled by mosaic of equant sparite.

Permian, New Mexico, USA

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15. Radiaxial Fibrous Cement

Clotted peloidal micrite microbial boundstone (visible in lower left corner) with several mms large primary cavities filled by radiaxial fibrous calcite cement. The sparse rhombic crystals of gray/light green colour are burial replacive dolomite.

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

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16. Fibrous Cement

Pisoidal-peloidal grainstone with sub-parallel mm thick rims of fibrous cement occasionally lined by micrite crusts.

Permian, New Mexico, USA

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17. Micritisation

Skeletal peloidal packstone to grainstone containing in the centre a cortoid: a skeletal grain with the outer rim micritised. The skeletal fragment, likely aragonitic, has been dissolved and replaced by equant calcite spar (burial diagenesis). Micritisation is generally produced by endolithic micro-organisms finely boring the outer rim of shells and it is typical of lagoonal environments.

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

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18. Micritisation

Cortoid packstone with several skeletal fragments coated by micrite envelopes. Most of the micrite envelopes are both destructive (microborings) and constructive (accretionary micrite algal-microbial coatings). The skeletal grains replaced by calcite spar mosaic (burial diagenesis) might have been aragonitic green algae.

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19. Stromatactis

Siliceous sponge mcirobial boundstone facies with stromatactis-like cavities. These are primary voids of undetermined origin with flat base and irregular tops usually filled by cement and common in mud mound litofacies. In this case: the cement is a rim of radiaxial fibrous calcite (marine diagenesis) followed by equant calcite spar (burial diagenesis).

Lower Jurassic, High Atlas, Morocco, cf. Della Porta et al. (2013)

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20. Stromatactis

Skeletal peloidal packstone belonging to a middle ramp sponge mound facies containing stromatactis-like voids lined by isopachous rims of radial fibrous cement (pink, non ferroan calcite) followed by drusy mosaic of calcite spar (blue, ferroan calcite). Thin section stained with alizarin red and k ferricyanide.

Lower Jurassic, High Atlas, Morocco, cf. Della Porta et al. (2013)

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21. Stromatactis

Peloidal skeletal (siliceous sponge spicules) wackestone from sponge mound facies in middle ramp with stromatactis-like cavity filled by isopachous rim of radial fibrous cement (marine) and mosaic of blocky sparite (burial).

Lower Jurassic, High Atlas, Morocco, cf. Merino-Tome' et al. (2012), Della Porta et al. (2013)

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22. Micritisation

Borings and thick micrite envelope showing microborings of the mollusc shell. Micritisation takes place mostly on shallow lagoon sea floor.

Upper Cretaceous (Turonian) Miskar Field, offshore Tunisia

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23. Aragonite cement

SEM image of aragonite acicular crystals (with square tops) forming ooids in recent tropical carbonate setting.

Recent, Turks & Caicos Islands

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24. Reef cement

SEM image of early marine High Mg calcite cement from Jamaican reef front, Discovery Bay.

Recent, Discovery Bay, Jamaica

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25. Fibrous cement

Isopachous rims of marine isopachous fibrous cement, locally polygonal in a skeletal grainstone with echinoderms and fusulinid (image in plane polarized light).

Carboniferous, Karachaganak Field, Kazakhstan

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26. Marine cement

Isopachous rims of marine isopachous fibrous cement, locally polygonal in a skeletal grainstone with echinoderms and fusulinid (image in cross-polarized light).

Carboniferous, Karachaganak Field, Kazakhstan

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27. Botryoidal aragonite

Replaced botryoidal aragonite, coated by radiaxial fibrous calcite, followed by anhydrite in the remaining pore space.

Permian, Karachaganak Field, Kazakhstan

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28. Botryoidal aragonite

Replaced botryoidal aragonite, coated by radiaxial fibrous calcite.

Permian, Karachaganak Field, Kazakhstan

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29. Aragonite microspar

Former aragonite microspar and accretionary micrite crusts interpreted as marine precipitation mediated by microbial activity (biologically induced precipitation). Field of view is approximately 3 mm wide.

Carboniferous, Karachaganak Field, Kazakhstan

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30. Peloidal micrite

Peloidal micrite and associated microsparite cement forming patch reefs in Jurassic limestone.

Upper Jurassic, SE England, UK

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31. Peloidal micrite

SEM image of previous peloidal micrite: the central clot of micrite is surrounded by a rim of calcite bladed microsparite.

Upper Jurassic, SE England, UK

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32. Fascicular optic calcite

Fascicular optic calcite showing inclusion-rich irregular crystals viewed in cross polarized light showing undulose extinction. Field of view approximately 2 mm wide.

Mississippian, Llanelly Formation, South Wales, UK

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33. Radiaxial fibrous calcite

Example of radiaxial fibrous calcite surrounding peloidal micrite. Field of view of approximately 2 mm.

Permian, Karachaganak Field, Kazakhstan

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34. Radiaxial fibrous calcite

Example of radiaxial fibrous calcite surrounding bryozoans. Field of view of approximately 3 mm.

Permian, Karachaganak Field, Kazakhstan

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35. Radiaxial fibrous calcite

Example of radiaxial fibrous calcite surrounding bryozoans. Field of view of approximately 3 mm.

Permian, Karachaganak Field, Kazakhstan

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36. Hardground

Intense marine cementation in hardground surfaces. Lower part is well cemented and the top is truncated and eroded with fibrous marine cement in open-packed oolite. Oysters attached to the hardground surface because they require hard substrates to attach on. The upper part is a compacted ooidal grainstone lacking early marine cement and cemented by ferroan calcite spar during burial (light blue staining).

Middle Jurassic, Cotswolds, UK

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37. Hardground

Lower part is well cemented and rich in Epimastopora dasycladacean algae. It is truncated by a sharp irregular hardground surface. The upper portion is a skeletal grainstone.

Carboniferous, Karachaganak Field, Kazakhstan

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38. Fibrous cement

Isopachous fibrous cement from a marine hardground in a Jurassic ooidal shoal. Marine cementation is followed by equant sparite of meteoric phreatic or burial diagenesis.

Middle Jurassic, Cotswolds, UK

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tangential aragonitic ooid

fibrous cement rims

tangential aragonitic ooid

fibrous cement rims

fibrous aragonitic rims

fibrous cement rims

Archaias

isopachous cement rim

botryoids of former aragonite

micrite crusts

former aragonite botryoids

peloids and micrite crusts

radiaxial fibrous calcite

radiaxial fibrous calcite

radial fibrous cement

equant calcite mosaic

radial fibrous cement

equant calcite mosaic

clotted peloidal micrite

radiaxial fibrous calcite

radiaxial fibrous calcite

pisoid

micrite crust lining fibrous cement

micrite envelope

calcite spar after aragonite dissolution

micrite envelope

radiaxial fibrous cement in stromatactis

non ferroan fibrous cement

ferroan equant calcite

stromatactis

boring

micrite envelope

aragonite crystals

calcite cement

isopachous fibrous cement

isopachous fibrous cement

botryoidal aragonite

isopachous cement

anhydrite

micrite crust

peloidal micrite

radiaxial fibrous calcite

clotted peloidal micrite

radiaxial fibrous calcite

bryozoan

radiaxial fibrous calcite

bryozoan

hardground encrusted by oyster

hardground

Epimastopora

isopachous cement

equant sparite

Marine

CLOSE

tangential aragonitic ooid

fibrous cement rims

tangential aragonitic ooid

fibrous cement rims

fibrous aragonitic rims

fibrous cement rims

Archaias

isopachous cement rim

botryoids of former aragonite

micrite crusts

former aragonite botryoids

peloids and micrite crusts

radiaxial fibrous calcite

radiaxial fibrous calcite

radial fibrous cement

equant calcite mosaic

radial fibrous cement

equant calcite mosaic

clotted peloidal micrite

radiaxial fibrous calcite

radiaxial fibrous calcite

pisoid

micrite crust lining fibrous cement

micrite envelope

calcite spar after aragonite dissolution

micrite envelope

radiaxial fibrous cement in stromatactis

non ferroan fibrous cement

ferroan equant calcite

stromatactis

boring

micrite envelope

aragonite crystals

calcite cement

isopachous fibrous cement

isopachous fibrous cement

botryoidal aragonite

isopachous cement

anhydrite

micrite crust

peloidal micrite

radiaxial fibrous calcite

clotted peloidal micrite

radiaxial fibrous calcite

bryozoan

radiaxial fibrous calcite

bryozoan

hardground encrusted by oyster

hardground

Epimastopora

isopachous cement

equant sparite