Carbonate compensation

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 Downcore profile of 6 Zn (Marechal et al. 2000) and 6 Cu values (unpublished) in Central Pacific core RC 17-203 (21° 50 S, 132° 53 W, z = 3900 m).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.

The marine carbonate system is thought to participate in another set of interlinked processes that acts to regulate atmospheric CO2 levels over time scales of 5 to lOky. This shorter cycle is commonly referred to as carbonate compensation and appears... 

A description of the carbonate compensation feedback system and its hypothesized roie in reguiating atmospheric CO2 ieveis is provided in the suppiementai information for Chapter 15.6 that is avaiiabie at http //elsevierdirect.eom/companions/9780120885305. 

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). 

Figures 5 and 6 present trends in dark/spark spreads and C02 costs per MWh over the years 2004—2005 in Germany and The Netherlands, based on forward (i.e. year-ahead) prices for power, fuels and C02 emission allowances. For the present analysis, a dark spread is simply defined as the difference between the power price and the cost of coal to generate 1 MWh of electricity, while a spark spread refers to the difference between the power price and the cost of gas to produce 1 MWh of electricity. If the costs of C02 are included, these indicators are called clean dark/spark spreads or carbon compensated dark/spark spreads/6...

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. 

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)...

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). 

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