Carbonate lysocline

Figure 4.20. Carbonate lysocline and carbonate critical depth (CCrD) variations with latitude in the Indian Ocean. Data from Bengal and Arabian fans are excluded. (After Kolia et al., 1976.)...

The solubility of calcite and aragonite increases with increasing pressure and decreasing temperature in such a way that deep waters are undersaturated with respect to calcium carbonate, while surface waters are supersaturated. The level at which the effects of dissolution are first seen on carbonate shells in the sediments is termed the lysocline and coincides fairly well with the depth of the carbonate saturation horizon. The lysocline commonly lies between 3 and 4 km depth in today s oceans. Below the lysocline is the level where no carbonate remains in the sediment this level is termed the carbonate compensation depth. 

Broecker, W. S. Takahashi, T. (1978). The relationship between lysocline depth and in situ carbonate ion concentration. Deep Sea Res., 25, 65-95. 

Lysocline The depth at which shell dissolution starts to have a detectable impact on the calcium carbonate content of the surface sediments. 

Kolia et al. (1976) plotted the lysocline and the carbonate critical depth (Figure 4.20) using methods similar to those of Biscaye et al. (1976). Unfortunately, they did not use the 0 weight % intercept of the CCD which appears to be generally 100 to 400 m deeper than the carbonate critical depth. Also, their use of the term lysocline is not the same as the FL, because it is entirely based on the relation between water depth and carbonate content of the sediment, not... 

It is also important to keep in mind that the relation between the saturation state of seawater and carbonate dissolution kinetics is not a simple first order dependency. Instead it is an exponential of about third to fourth order (e.g., Berner and Morse, 1974). Thus dissolution rates are very sensitive to saturation state. This type of behavior has not only been demonstrated in the laboratory (see Chapter 2), but also has been observed in numerous in situ experiments in which carbonate materials and tests have been suspended in the oceanic water column. The depth at which a rapid increase in dissolution rate with increasing water depth is observed usually has been referred to as the chemical or hydrographic lysocline. In some areas of the ocean it is close to coincident with the FL (e.g., Morse and Berner, 1972). 

Morse J.W. (1974) Dissolution kinetics of calcium carbonate in seawater. V Effects of natural inhibitors and the position of the chemical lysocline. Amer. J. Sci. 274, 638-647. 

Peterson L.C. and Prell W.H. (1985a) Carbonate dissolution in recent sediments of the eastern equatorial Indian Ocean Preservation patterns and carbonate loss above the lysocline. Mar. Geol. 64, 259-290. 

In these days following the plate tectonic revolution in natural science, there has been an increased propensity for specialization among scientists. This trend is apparent in the field of study of the geochemistry of sedimentary carbonates. Chemical oceanographers deal with the chemistry of the carbonic acid system in seawater. Some marine geologists and geochemists concern themselves with the relationship between factors controlling the lysocline and carbonate compensation... 

Figure 7. The depth distribution of the Ro and calcite saturation levels, the foraminiferal lysocline and the calcium carbonate compensation depth in the Western and Eastern Atlantic Ocean (after Ref. 40)...

Edmond, J.M. An interpretation of the calcite spheres experiment [abst.], Amer. Geophys. Union 52, 256 (1971). Morse, J.W. and Berner, R.A. Dissolution kinetics of calcium carbonate in sea water II. A kinetic origin for the lysocline, Amer. Jour. Sci. 272, 840-851 (1972). ... 

The carbonate compensation depth (CCD) occurs where the rate of calcium carbonate dissolution is balanced by the rate of infall, and the calcium carbonate content of surface sediments is close to Owt.% (e.g., Bramlette, 1961). The CCD has been confused with the calcium carbonate critical depth (sometimes used interchangeably with the lysocline discussed next), where the carbonate content of the surface sediment drops below 10 wt.%. A similar marker level in deep-sea sediments is the ACD, below... 

Lysocline the level or depth in an ocean below which there is a significant increase in the solution of calcium carbonate. 

A sketch of the carbonate content of deep sea sediments as a function of depth. Lighter shades indicate greater CaC03 content in the sediments. Horizontal arrows indicate theoretical relations among the depths of the lysocline (where CaCOs shows visible signs of dissolution), the carbonate compensation depth, CCD (where the CaCOs concentration drops to zero) and the saturation horizon (S =l). 

Below the lysocline a depth is reached at which the rate of supply of carbonate particles equals the rate of dissolution, termed the carbonate compensation depth (CCD). Below the CCD no carbonate is de-... 

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