Non-Skeletal Grain types

Oncoids

1. Oncoids

Fitted grainstone/rudstone (sutured grain contacts due to compaction and pressure solution) with several mm-size oncoids attributed to the cyanobacteria Garwoodia (transgressive subtidal phase at base of peritidal cyclothems).

Mississippian, South Wales

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2. 2) Oncoids

Oncoidal coating possibly formed by cyanobacterial and encrusting foraminifera surrounding an ooidal coating developed around a bryozoan fragment (subtidal lagoon).

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

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3. 3) Oncoids

Oncoids developed around phylloid algae; possible Osagia oncoid type (subtidal lagoon).

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

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4. 4) Oncoids

In the centre, oncoid of algal-foraminiferal encrustations around a brachiopod shell with borings.

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5. 5) Oncoids

Oncoidal packstone with intraclasts (stained with alizarin red).

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6. 6) Oncoids

Oncoid algal encrustation with serpulid worms in upper right corner.

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7. 7) Oncoids

Coralline red algae oncoids (rhodoids) in a packstone (Miocene).

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

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8. 8) Oncoids

Coralline red algae oncoids (rhodoids) with encrusting acervulinid foraminifera (Eocene).

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

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9. 9) Oncoids

Packstone containing ooids and oncoids likely formed by algal-cyanobacterial coatings.

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10. 10) Oncoids

Rudstone/packstone containing oncoids and micrite coated grains from Lower Jurassic middle ramp, Morocco.

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

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11. 11) Oncoids

Polished slab showing centimetre-size oncoids from Lower Carboniferous (Mississippian) inner ramp facies.

Mississippian, South Wales

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12. 12) Oncoids

Several millimetres in diameter oncoid consisting of the cyanobactria Garwoodia from Lower Carboniferous (Mississippian) inner ramp facies. Field of view nearly 6 mm.

Mississippian, South Wales

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13. 13) Oncoids

Skeletal oncoidal packstone with detrital quartz grains

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14. 14) Oncoids

Oncoids from Middle Jurassic shallow water carbonates with micritic encrustations around mollusc shells.

Middle Jurassic, UK

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15. 15) Oncoids

Oncoids from Middle Jurassic shallow water carbonates with micritic encrustations around mollusc shells.

Middle Jurassic, UK

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16. 16) Oncoids

Oncoids from Middle Jurassic shallow water carbonates with micritic encrustations around mollusc shells.

Middle Jurassic, UK

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17. 17) Oncoids

Packstone containing oncoids and micrite coated grains coating siliceous sponge spicules, whole hexactinellid siliceous sponge bodies and echinoid spines from Lower Jurassic middle ramp, Morocco.

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

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Garwoodia oncoid

sutured grain contacts

oncoidal coating

ncoidal coating on phylloid alga

boring on brachiopod

oncoid

oncoid

serpulids encrusting oncoid

red coralline algae oncoid

red alga oncoid

acervulinid foraminifer

sponge spicules

echinoid spine

Oncoids

CLOSE

Garwoodia oncoid

sutured grain contacts

oncoidal coating

ncoidal coating on phylloid alga

boring on brachiopod

oncoid

oncoid

serpulids encrusting oncoid

red coralline algae oncoid

red alga oncoid

acervulinid foraminifer

sponge spicules

echinoid spine