Carbonate compensation depth (CCD) is a level in the oceans below which the rate of supply of calcium carbonate (calcite and aragonite) equals the rate of dissolution, such that no calcium carbonate is preserved. Doubly refracting Calcite from Iceberg claim, Dixon, New Mexico. ... Aragonite Aragonite is a polymorph of the mineral calcite, both having the chemical composition CaCO3. ...

Calcium carbonate is essentially insoluble in sea surface waters today, shells of dead calcareous plankton sinking to deeper waters are practically unaltered until reaching the lysocline where the solubility increases dramatically, by the time the CCD is reached all calcium carbonate has dissolved. Photomontage of plankton organisms Plankton are drifting organisms that inhabit the water column of oceans, seas, and bodies of fresh water. ... The lysocline is a term used in geology, geochemistry and marine biology to denote the depth in the ocean below which the rate of dissolution of calcite increases dramatically. ...

Calcareous plankton and sediment particles can be found in the water column above CCD and, if the sea bed is above the CCD, bottom sediments can consist of calcareous sediments called calcareous ooze which is essentially a type of limestone or chalk. If the sea bed is below the CCD tiny shells of CaCO₃ will dissolve before reaching this level so there will be no carbonate sediment. Photomontage of plankton organisms Plankton are drifting organisms that inhabit the water column of oceans, seas, and bodies of fresh water. ... The pelagic zone is the part of the open sea or ocean comprising the water column, i. ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ... Pelagic sediments, also known as marine sediments, are those that accumulate in the abyssal plain of the deep ocean, far away from terrestrial sources that provide terrigenous sediments; the latter are primarily limited to the continental shelf, and deposited by rivers. ... Limey shale overlaid by limestone. ... The Needles, part of the extensive Southern England Chalk Formation Chalk is a soft, white, porous form of limestone composed of the mineral calcium carbonate. ...

The exact depth of the CCD depends on the solubility of calcium carbonate which is determined by temperature, pressure and the chemical composition of the water - in particular the amount of dissolved CO₂ in the water. Calcium carbonate is more soluble at low temperatures.

At the present time the CCD in the Pacific Ocean is about 4,200-4,500 m except beneath the equatorial upwelling zone, where the CCD is about 5,000 m. In the temperate and tropical Atlantic Ocean the CCD is at approximately 5,000 m. In the Indian Ocean it is intermediate between the Atlantic and the Pacific. The CCD is relatively shallow in high latitudes. Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-deplete surface water. ...

In the geological past the depth of the CCD has shown significant variation. For example, in the Cretaceous through to the Eocene the CCD was much shallower globally. In the late Eocene the development of Antarctic glaciers resulted in colder deep sea temperatures leading to a deeper CCD. The Cretaceous period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic period, about 146 million years ago (Ma), to the beginning of the Paleocene epoch of the Tertiary period (65. ... The Eocene epoch (56-34 Ma) is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era. ...

Sir John_Murray (oceanographer) investigated and experimented on the dissolution of calcium carbonate and was first to identify the carbonate compensation depth in oceans. Sir John Murray (March 3, 1841 - March 16, 1914), pioneering Scots-Canadian oceanographer and marine biologist. ...