Oolite

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Close-up of an oolite from the Central Jurassic Carmel Formation in Utah (USA). Scale bar = 0.5 mm
Oolite quarry near Arco (Trentino)

Oolite ( egg stone , from Greek ᾠόν oon , "egg" and λίθος lithos , "stone") is a sedimentary rock that consists of small mineral spheres ( ooids ) that are cemented by a calcareous or clayey binder. The ooids consist mainly of lime ( calcite or aragonite : roe stone , pea stone ), iron hydroxide (ironoolite) or of silica (kieseloolite, mostly silicified calcoolite). They have a generally diameter of 0.5 to 2 millimeters.

Ooids arise in warm, lime-saturated water with strong waves. The starting point for ooid formation are small particles such as B. Grains of sand or fragments of mussel shells, which are kept in suspension by the wave movement and form crystallization nuclei on which lime is deposited in concentric shells or in the form of radial- fibrous calcite crystals . If these ooids have become too heavy, they sink to the bottom of the sea and form a layer of sediment in which they are rolled by the movement of water. Oolite results from the solidification of this sediment layer into rock ( diagenesis ).

Oolite or Rogenstein is eponymous for various rock formations , for example for the Jurassic formations Korallenoolith , Murchisonaeoolith Formation and Hauptrogenstein as well as the natural stone type Braunschweiger Rogenstein from the lower red sandstone ( Lower Triassic).

literature

  • Hans Murawski: Geological Dictionary . 8th edition. Ferd. Enke Verlag, Stuttgart 1983, ISBN 978-3-432-84108-3 .
  • Dieter Richter: General Geology . 3. Edition. de Gruyter Verlag, Berlin - New York 1985, ISBN 3-11-010416-4 .

Web links

Commons : Oolith  - collection of images, videos and audio files