Calcareous
Calcareous (
In zoology
Calcareous is used as an adjectival term applied to anatomical structures which are made primarily of calcium carbonate, in animals such as
The
Additionally, reef-building corals, or Scleractinia, are calcareous organisms that form their rigid skeletal structure through the precipitation of aragonite (i.e., a polymorph of calcium carbonate).[2]
In botany
Calcareous grassland is a form of grassland characteristic of soils containing much calcium carbonate from underlying chalk or limestone rock.
In medicine
The term is used in pathology, for example in calcareous conjunctivitis, and when referring to calcareous metastasis or calcareous deposits, which may both be removed surgically.
In geology
The term calcareous can be applied to a sediment, sedimentary rock, or soil type which is formed from, or contains a high proportion of, calcium carbonate in the form of calcite or aragonite.
Marine sediments
Calcareous sediments are typically deposited in shallow water closer to land, as marine organisms that precipitate calcium carbonate primarily reside within shallow water ecosystems due to an inability to precipitate calcium carbonate at depth (see carbonate compensation depth). Generally speaking, the farther from land sediments fall, the less calcareous they are, and deviations from this expectation arise if (a) the ocean floor is shallower than the CCD or (b) storms/ocean currents transport calcareous sediments away from their origin point, leading to the interbedding of calcareous sediments in alternative locations.
An additional form of calcareous marine sediment consists of calcareous ooze, which is a form of calcium carbonate sediment that consists of >30% biogenous material predominantly consisting of organisms such as coccolithophores and foraminifera.[3] These oozes form slowly under low-energy environments, and necessitate higher seawater saturation states or a deeper CCD (see supersaturation and precipitation vs. undersaturation and dissolution). Therefore, in shallow CCD conditions (i.e., undersaturation of calcium carbonate at depth), stable, non-calcareous sediments such as siliceous ooze or pelagic red clay will prevail in marine sediment records.
Calcareous soils
Calcareous soils are relatively
List of calcareous rivers
- Ganga
Man made deposits
In electrochemistry
Calcareous coatings, or calcareous deposits, are mixtures of calcium carbonate and magnesium hydroxide that are deposited on cathodically protected surfaces because of the increased pH adjacent to the surface.
References
- ISBN 0-87850-138-X.
- hdl:2115/86637. Retrieved 15 February 2024.
- ^ "Oozes". Geosciences LibreTexts: Miracosta Oceanography 101. LibreTexts Libraries. Retrieved 15 February 2024.
- ^ "Diagnostic horizons, properties and materials". Lecture notes on the major soils of the world. FAO. Retrieved 14 June 2014.
- ^ S2CID 140166525. Retrieved 17 July 2018.