Carbonate compensation depth

Biogenic Ma.teria.ls, Deep ocean calcareous or siUceous oo2es are sediments containing >30% of biogenic material. Foraminifera, the skeletal remains of calcareous plankton, are found extensively in deep equatorial waters above the calcium carbonate compensation depth of 4000 to 5000 m. 

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. 

Figure 5. Downcore profile of 6 Zn (Marechal et al. 2000) and 6 Cu values (unpublished) in Central Pacific core RC 17-203 (21° 50 S, 132° 53 W, z = 3900 m). The water-sediment interface is located below the carbonate compensation depth and deep-sea clays dominate the mineralogy of the samples.

Calcite compensation depth See Calcium carbonate compensation depth. 

Calcium carbonate compensation depth (CCD) The depth below which calcium carbonate is not found in marine sediments due to its dissolution. 

Carbonate compensation The ocean s response to perturbations through shifts in its carbonate chemistry. These shifts require changes in the carbonate ion concentration that change the depth of the calcium carbonate compensation depth and hence lead to changes in the burial rate of carbon as biogenic calcium carbonate. 

Ben-Yaakov, S., Ruth, E., and Kaplan, I. R. Carbonate compensation depth Relation to carbonate solubility in ocean waters. Science 184, 982-984 (1974). 

Figure 10.20. Comparison of some trends through the Cenozoic. A. The 8180 content of benthic foraminifera (Savin et al., 1975 see also Prentice and Matthews, 1988). If the 5180 trend is primarily due to temperature, Cretaceous deep water temperatures were about 12°C warmer than today. B. Progressive change of the North Atlantic and Pacific carbonate compensation depth (CCD van Andel, 1975). C. The Sr/Ca ratio of planktonic foraminifera (Graham et al., 1982). D. Ridge volume (Pitman, 1978).

Pytkowicz R.M. (1970) On the carbonate compensation depth in the Pacific Ocean. Geochim. Cosmochim. Acta 34, 836-839. 

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)...

There are several other topics that would be equally appropriate to consider in a review of this type. Some of these, such as the record of seawater and the history of the calcium carbonate compensation depth (CCD), are mentioned briefly as they relate to records that are discussed in greater detail. Other topics have been omitted. We hope readers will recognize that the topics covered here are determined not only by the scientific interests of the authors, but also by the practical limits of what can be covered in a single review. 

In the equatorial Pacific (8°40 N-10°10 N, 173°50 W-175° W), several 6-7 m long cores and many surface sediment samples at water depths of —6,000 m (below the carbonate compensation depth) were collected during the... 

Fagel et al. (1997, personal communication) provided major and trace element data for hve piston cores (20-30 m long) taken from the central Indian Basin at water depths —4,800-5,400 m (below the carbonate compensation depth). Additional Sr/ Sr and Nd/ Nd data for some samples are given by Fagel et al. (1994). Biogenic silica (mainly radiolarian tests... 

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... 

Carbonate compensation depth the level of an ocean at which the rate of calcium carbonate deposition equals the rate of its resolution. 

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). 

Although the ratio of 180 160 in carbonate tests of marine invertebrates can be used to examine sea surface temperatures, the extent of continental glaciation, the balance between precipitation and evaporation, the carbonate compensation depth and the diagenetic alteration of carbonate all influence whether an estimation can be made and its accuracy (Boxes 5.6, 5.7 Marshall 1992). There is also a reliable organic geochemical palaeothermometer based on the distributions of long-chain (C37-C39) unsaturated ketones (Brassell et al. 

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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