oolite


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oolite

(ō`əlīt, ō`ō–), rock composed of small concretions, usually of calcium carbonate, containing a nucleus and clearly defined concentric shells. In the British Isles oolitic limestone is characteristic of the middle and upper Jurassic, which was formerly termed the Oolite on this account.

Oolite

 

(according to some sources, oolith), a spheroidal or ellipsoidal formation consisting of oxides and silicates of iron and manganese and of calcite, dolomite, aragonite, rhodochro-site, leptochlorite, and other minerals. Oolites range in size from several microns to 15–25 mm. Oolites larger than 2–5 mm are called pisolites. In the center of an oolite there is usually—but not always—a grain of sand or a fragment of the calcareous shell of some organism, around which thin layers of the precipitating substance accrete; as a result the structure of oolites is usually concentric-botryoidal. Oolites with radial and complex structures (combinations of concentric-botryoidal and radial structures) are also found. Oolites form in seawater and warm springs as a result of colloid-chemical and biochemical processes. Ferruginous oolites are a variety of iron ore.

REFERENCE

Shvetsov, M. S. Petrografiia osadochnykh porod, 3rd ed. Moscow, 1958.

V. A. GROSSGEIM

oolite

[′ō·ə‚līt]
(petrology)
A sedimentary rock, usually a limestone, composed principally of cemented ooliths. Also known as eggstone; roestone.

oolite

A granular limestone, each grain of which is more or less spherical and made up of concentric coats of carbonate of lime formed around a nucleus.

oolite

any sedimentary rock, esp limestone, consisting of tiny spherical concentric grains within a fine matrix
References in periodicals archive ?
It has a deeper Minagish Oolite Fm producing heavy oil, and a Lower Jurassic Marrat Fm with large reserves of light oil.
The resources are an aggregate of two separate oil columns, one within conventional Purbeck and Portland limestone reservoirs and a deeper one within a conventional Inferior Oolite limestone reservoir.
Two silt and shale lentils mark the base of the Spar Mountain Member and the upper Fredonia bed is a thick sparry oolite.
According to LOOK (1985: 393), the sediments of the Lower and Middle Coral Oolite are marine; up section, starting with the Upper Coral Oolite, environments became more and more brackish (see figure 1).
Geologically, it is in the wrong county, the proof being the golden acres of Inferior Oolite - or honey Cotswold stone - but there is nothing inferior about Broadway or its prized position at the foot of the Cotswold hills.
He did not like this vision, and yet, a child of his time, found it compelling, somehow guaranteed to be significant, as a geological survey of oolite would not be.
Figure 3 illustrates this phenomenon and the controlling factors for the well-studied Cenozoic limestones and dolostones from Florida and the Jurassic Smackover oolite reservoirs in the southern United States.
Strata exposed at the study site were assigned to seven lithofacies based upon sedimentologic, paleontologic and petrographic characteristics: (A) Oolite, (B) Skeletal, (C) in situ Coral, (D) Coral Floatstone, (E) Cross-stratified Skeletal Grainstone, (F) Fenestral, and (G) Breccia.
Separating these two units is central oolite sequence (70m), termed the Lisduff Oolite.
The interiors of the shallow Cretaceous and Eocene carbonate caps range from shallow subtidal environments characterized by oolite shoals, occasionally deepening into depths of perhaps 10 to 20 meters with rudist banks, to supratidal depositional environments.