Lysocline

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. 

Rondo-Bron (Mack)-comb. with guaiphenesin wfm Rondomycin (Mack) wfm F Lysocline (Parke Davis)... 

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. 

The foraminiferal lysocline (FL) was defined by Berger (1968) as the depth where the predominant type of foraminifera shifts in surface sediments, because of dissolution, from "soluble" to "resistant" species ( 50% change in ratio). To determine the depth of the foraminiferal lysocline, three conditions must be met (Parker and Berger, 1971) ... 

There must be sufficient topographic relief so that sediment samples from both above and below the foraminiferal lysocline can be obtained. 

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... 

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.)...

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). 

Berger W.H. (1970) Planktonic Foraminifera Selective solution and the lysocline. Mar. Geol. 8, 111-138. 

Morse J.W. (1973) The dissolution kinetics of calcite A kinetic origin for the lysocline. Ph.D. dissertation, Yale Univ. 

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. 

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)...

Figure 9. Relationship between the distance from equilibrium (1 — Q) of seawater with respect to calcite and the amount of dissolution which is estimated to have occurred. (A) Adelseck s (11) experimentally determined amount of dissolution (B) Berger s (12) minimum loss estimate for the amount of dissolution at the Ro level and foraminiferal lysocline.

Figure 11. Plot of the Peterson (41) and Berger (42) results for their water-column dissolution experiments in the Central Pacific Ocean, and the Morse and Berner (45) laboratory experiments as a function of equivalent depth. The depth of the lysocline was calculated from the data of Bramlette (49) (after Bef. 45).

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). ... 

Archer D. E. (1996b) A data-driven model of the global calcite lysocline. Global Biogeochem. Cycles 10, 511-526. 

Sigman D. M., McCorkle D. C., and Martin W. R. (1998) The calcite lysocline as a constraint on glacial/interglacial low latimde production changes. Global Biogeochem. Cycles 12, 409-428. 

Figure 11 A sketch of the theoretical relationships among the depths of the lysocline, the CCD, and the saturation horizon (Cl = 1). Dot density represents relative CaC03 content in the sediments.

---