Grainstone

1. Grainstone

Grain-supported; cement (calcite spar) in interparticle pore space between skeletal grains (bivalves, gastropods) and peloids.

2. Grainstone

Grainstone observed in parallel polarizers: grain-supported texture with porosity in interparticle space and cement (meniscus calcite cement at grain contacts of vadose meteoric diagenesis) surrounding peloids and partially leached micritized ooids.

Bahamas, Pleistocene

3. Grainstone

Grainstone observed in crossed polarizers (previous ooidal peloidal grainstone): grain-supported texture with cement (meniscus calcite cement of vadose meteoric diagenesis) and porosity in interparticle space.

Bahamas, Pleistocene

4. Grainstone

Grainstone: grain-supported; cement (isopachous rims of fibrous cement of marine diagenesis) binding grains (ooids).

5. Grainstone

Open-packing ooidal grainstone with calcite spar cement surrounding radial-concentric ooids and an ostracod near the top of the image.

Mississippian, Chipping Sodbury, England, UK

6. Grainstone

Peloidal grainstone (grain-supported, calcite spar cement) with sparse echinoid spines representing a calcareous turbidite bed.

Jurassic, Peniche, central Portugal

7. Grainstone

Porous peloidal and coated grain grainstone with intergranular porosity put in evidence by blue epoxy.

Cretaceous (upper Turonian), Miskar Field, offshore Tunisia

8. Grainstone

Peloidal skeletal grainstone with benthic foraminifera, minor interparticle porosity (blue epoxy) and marine isopachous cement.

Cretaceous (upper Turonian), Miskar Field, offshore Tunisia

9. Grainstone

Skeletal grainstone with minor porosity (blue epoxy). Skeletal fragments are rudist bivalves.

Cretaceous (upper Turonian), Miskar Field, offshore Tunisia

10. Grainstone

Skeletal grainstone with fusulinid and staffellid foraminifera, fragments of dasyclad green algae (Epimastopora) and echinoderms.

Lower Permian, Karachaganak oil field, Kazakhstan

11. Grainstone

Skeletal grainstone with fusulinid and staffellid benthic foraminifera, mollusc biomoulds and echinoderms.

Lower Permian, Karachaganak oil field, Kazakhstan

12. Condensed grainstone

Grain-supported, diagenetic texture due to compaction and pressure solution with partial grain suturing: some grain contacts are microstylolites. Locally blocky spar cement present between skeletal grains: foraminifera (Lepidocyclina, Nummulites, Miogypsoinoides) and bryozoans.

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

13. Fitted grainstone

Grain-supported, diagenetic texture due to compaction and pressure solution with complete grain suturing: all grain contacts are microstylolites. No cement or matrix present between grains.

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

14. Fitted grainstone

Grain-supported, diagenetic texture due to compaction and pressure solution with complete grain suturing: all grain contacts are microstylolites. No cement or matrix present between grains.

15. Grainstone

Peloidal skeletal grainstone with a crinoid ossicle (on the left) affected by pressure solution crossed by a stylolite crossing diagonally.

Mississippian, South Wales, UK