Calcite compensation depth

Calcite compensation depth See Calcium carbonate compensation depth. 

Takahashi, T. Carbonate chemistry of seawater and the calcite compensation depth in the oceans, p. 11-26, ... 

At about 4000 m water depth, carbonate tests are dissolved, because their solubility depends on pressure (this depth in the ocean is called calcite compensation depth, abbreviated CCD). With the dissolution of tests the metals collected before are again liberated and can contribute to the growth of manganese nodules. 

By mapping the depth at which carbonate sediments exist on the floors of the oceans, it is possible to identify the level where the rate of supply of biogenic CaC03 is balanced by the rate of solution. This depth, known as the calcite compensation depth (CCD), is variable in the world s oceans, depending on the... 

Fig. 6.11 Schematic diagram showing depth relationship between degree of saturation for calcite in seawater and rate of CaC03 dissolution. At 4km depth, as seawater approaches undersaturation with respect to calcite, rate of dissolution of sinking calcite skeletons increases. The lysocline marks this increased rate of dissolution. Below the lysocline only large grains (foraminifera) survive dissolution if buried in the seabed sediment. Below the calcite compensation depth (CCD see text) all CaC03 dissolves, leaving red clays.

A third example is the increasing solubility of calcite with depth in the ocean. Surface seawater is generally supersaturated with respect to calcite, whereas at depths below about 500 m the oceans become undersaturated with calcite (cf. Drever 1988). For this reason there is a tendency for carbonate materials to dissolve and disappear with increasing depth as they settle into ocean bottom sediments. Reasons for the shift to undersaturation with increasing ocean depth include declining temperatures, increased pressure (see Chap. 1, Section 1.6.2), and increasing CO2 concentrations. The depth at which a pronounced reduction in the carbonate content of ocean sediments is observed is termed the calcite compensation depth (CCD). Because of the slow rate at which the calcite dissolves, the CCD is found well below the approximately 500 m depth at which calcite becomes undersaturated. The CCD is thus at about 3.5 km depth in the Pacific Ocean and 5 km depth in the Atlantic Ocean (Drever 1988). 

The sediments in the deep sea consist of only few basic types which in their manifold combinations are suited for the description of a varied facial pattern (Table 1.4). The characteristic pelagic deep-sea sediment far from coastal areas is deep-sea red clay, an extremely fine-grained (median < 1 pm) red-brown clay sediment which covers the oceanic deep-sea basins below the Calcite Compensation Depth (CCD). More than 90 % is composed of clay minerals, other hydrogenous minerals, like zeolite, iron-manganese precipitates and volcanic debris. Snch sediment composition demonstrates an anthigenic origin. The... 

This section primarily focuses on the description of the deposition and accumulation of carbonates in shallow waters and in the deep ocean. The main depocenters for calcium carbonates are the continental shelf areas, as well as island arcs or atolls, which are the typical shallow water environments for massive carbonate formation, and the pelagic deep-sea sediments above the calcite compensation depth catching the rain of small calcareous tests formed by marine plankton in the surface waters. 

At which water depth would you expect the calcite compensation depth (CCD) in waters of high latitudes and in which water depth in waters of low latitudes Explain your answer. 

CaCOs production comprises the total amount produced in the surface waters. Accumulation is the - much smaller - portion which becomes buried in the deeper sediment. The difference between both comprises the dissolution in the water column and in the upper parts of the young sediment, from where dissolved inorganic carbon (DIC) still can be transferred to the bottom water. Thus the sediment below the calcite compensation depth (CCD) is characterized by no calcite accumulation. Below the CCD calcite particles may reach the seafloor and may even be found in the upper few decimeters of the young sediment, but they will be dissolved according to processes of early diagenesis. 

At high latitudes the calcite compensation depth (CCD) is at a water depth of about 3000 m, whereas in low latitudes the CCD is at a depth of about 5000 m. The undersaturation with respect to calcite of the deep ocean is caused by cold water, which sinks to the seafloor at high latitudes and flows as deep water current towards the low latitudes. The closer the deep current comes to the low latitudes, the more calcite from the production in surface waters is dissolved in the upper parts of the deep current. Thus the CCD of the deep water current is continuously lowered on the way from high to low latitudes. 

The association of marine barite with organic matter complicates the interpretation of occurrence of increased barite deposition found along midocean ridges because greater preservation of organic matter also occurs with increased carbonate sedimentation above the calcite compensation depth. Additionally, basin-scale dispersal of hydrothermal particles appears limited, especially for the relatively dense barite. Studies of marine barite saturation show that barite is below saturation in the water column but rapidly approaches saturation in the pore waters of deep-sea sediments. Discrete barite particles are nevertheless found in the microenvironments of suspended... 

Van Andel TH (1975) Mesozoic-Cenozoic calcite compensation depth and the global distribution of calcareous sediments. Earth and Planetary Science Letters 26 187-194. 

The mineral calcite is one of the most prominent phases in deep sea sediments. Its distribution with water depth on the flanks of the oceanic ridges everywhere in the world oceans has the same basic character. Sediments with uniformly high calcite content extend from the crest down the ridge flank to what Berger (1968) has teimed the lysocline. Here a decrease in calcite content with water depth commences. This decrease continues imtil sediments nearly free of calcite are encountered. Below this horizon (often referred to as the calcite compensation depth) the sediments are free of calcite. Although the pattern is everywhere the same the depth of the lysocline and the width of the transition zone (i.e. distance between lysocline and compensation depth) vary from basin to basin (see Fig. l). 

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