page_title: Ooid
hierarchical_section_title: Ooid
caption_attribution_description: Français&#160;: Coupe/lamelle d'ooide calcaire de la formation du Carmel, Jurassique-moyen, Sud de l'Utah (USA). Les nucléus (noyaux autour desquels les ooïdes se sont constitués sont bien visibles. English: Ooids in thin-section; Carmel Formation; Jurassic of Utah. [1]
context_page_description: Ooids are small, spheroidal, "coated" sedimentary grains, usually composed of calcium carbonate, but sometimes made up of iron- or phosphate-based minerals. Ooids usually form on the sea floor, most commonly in shallow tropical seas. After being buried under additional sediment, these ooid grains can be cemented together to form a sedimentary rock called an oolite. Oolites usually consist of calcium carbonate; these belong to the limestone rock family. Pisoids are similar to ooids, but are larger than 2 mm in diameter, often considerably larger, as with the pisoids in the hot springs at Carlsbad in the Czech Republic.
context_section_description: Ooids are small (commonly ≤2 mm in diameter), spheroidal, "coated" (layered) sedimentary grains, usually composed of calcium carbonate, but sometimes made up of iron- or phosphate-based minerals. Ooids usually form on the sea floor, most commonly in shallow tropical seas (around the Bahamas, for example, or in the Persian Gulf). After being buried under additional sediment, these ooid grains can be cemented together to form a sedimentary rock called an oolite. Oolites usually consist of calcium carbonate; these belong to the limestone rock family. Pisoids are similar to ooids, but are larger than 2 mm in diameter, often considerably larger, as with the pisoids in the hot springs at Carlsbad (Karlovy Vary) in the Czech Republic.
caption: A thin slice of calcitic ooids from the Carmel Formation, Middle Jurassic, of southern Utah, USA.
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