Carbonate sedimentation

Owing to the stability of the uranyl carbonate complex, uranium is universally present in seawater at an average concentration of ca. 3.2/rgL with a daughter/parent activity ratio U) of 1.14. " In particulate matter and bottom sediments that are roughly 1 x 10 " years old, the ratio should approach unity (secular equilibrium). The principal source of dissolved uranium to the ocean is from physicochemical weathering on the continents and subsequent transport by rivers. Potentially significant oceanic U sinks include anoxic basins, organic rich sediments, phosphorites and oceanic basalts, metalliferous sediments, carbonate sediments, and saltwater marshes. " ... 

Almost all the Earth s carbon is found in the lithosphere as carbonate sediments that have precipitated from the oceans. Shells of aquatic animals also contribute CaC03 to the lithosphere. Carbon returns to the hydrosphere as carbonate minerals dissolve in water percolating through the Earth s crust. This process is limited by the solubility products for carbonate salts, so lithospheric carbonates represent a relatively inaccessible storehouse of carbon. 

Liu Y.-G. and Schmitt, R.A. (1993b) Earth s partial pressure of CO2 over the past 100-500 Ma evidence from Ce anomalies to mostly shallow seas (<200 m) as recorded in carbonate sediments. Lunar Planet. Sci., XXIV, 885-886. 

Limestone. Limestone usually occurs as a white or light-shaded sedimentary monomineral formed by the consolidation of calcite (composed of calcium carbonate) sediments. It is a soft rock that can easily be cut and shaped into any size and form, so it has been used, since early antiquity, for... 

Soil Organic Carbon Sediment Organic Carbon... 

I apply these computational methods to various aspects of the Earth system, including the responses of ocean and atmosphere to the combustion of fossil fuels, the influence of biological activity on the variation of seawater composition between ocean basins, the oxidation-reduction balance of the deep sea, perturbations of the climate system and their effect on surface temperatures, carbon isotopes and the influence of fossil fuel combustion, the effect of evaporation on the composition of seawater, and diagenesis in carbonate sediments. These applications have not been fully developed as research studies rather, they are presented as potentially interesting applications of the computational methods. 

Chapter 8 describes a similar one-dimensional chain of identical reservoirs, but one that contains several interacting species. The example illustrated here is the composition of the pore waters in carbonate sediments in which dissolution is occurring as a result of the oxidation of organic matter. I calculate the concentrations of total dissolved carbon and calcium ions and the isotope ratio as functions of depth in the sediments. I present... 

These three numerical experiments show how the waters of an evaporating lagoon respond differently to the different seasonal perturbations that might affect them. Some record of these perturbations might, in principle, be preserved in the carbonate sediments precipitated in the lagoon. All three perturbations—productivity, temperature, and evaporation rate— cause seasonal fluctuations in the saturation state of the water and in the rate of carbonate precipitation. Temperature oscillations have little effect on the carbon isotopes. Although seasonally varying evaporation rates affect 14C, they have little effect on 13C. Productivity fluctuations affect both of the carbon isotopes. 

I shall apply the new method of solution to a problem of early diagenesis in carbonate sediments. I calculate the properties of the pore fluid in the sediment as a function of depth and time. The different reservoirs are... 

I consider a system in which organic matter is oxidized at a steady rate that is a specified function of depth in uniform calcium carbonate sediments. The oxidation of organic matter increases the total dissolved carbon in the pore water of the sediment. The resultant increase in acidity causes the dissolution of calcium carbonate and a consequent increase in alkalinity as well as another increase in total dissolved carbon. The total dissolved carbon and alkalinity are transported by diffusion between different depths in the sediment. 

Program SEDS01 solves diagenesis in carbonate sediments Equal layer thicknesses... 

Dissolution of carbonated sediments is, probably unduly (Broecker and Peng, 1982), neglected. 

While all the living matter in the oceans contains only about 3 billion tons of carbon, ten thousand times that amount is dissolved in the oceans, mostly in nonliving form. The carbonate sediments in the continental crust and the ocean floor contain almost 70 million billion tons of carbon. These are huge quantities compared to the atmosphere and living and dead biota. 

Table 4.6 (opal, carbonate and aluminosilicate) were chosen to provide end members for matrix analysis. These samples also could be blended to produce any mixture desired. Sampling sediments from well-studied depositional regions such as MANOP Site R in the North Pacific (for open-ocean red clay) and Florida Bay (for carbonate sediments) would offer a variety of supplemental information that is already available. In addition, the (Atchafalaya) river sediment would provide a useful link between those studying terrestrial and marine processes. 

Carter, P.W., and R.M. Mitterer. 1978. Amino acid composition of organic matter associated with carbonate and non-carbonate sediments. Geochimica et Cosmochima Acta 58 1231-1238. 

You CF, Chan LH, Gieskes JM, Klinkhammer GP (2004) Seawater intrusion through the oceanic crust and carbonate sediment in the Equatorial Pacific Lithium abundance and isotopic evidence. Geophys Res Lett 30 (in press)... 

The calcium carbonate shells of marine microfauna are a large repository of terrestrial calcium and constitute a potential record of changes in the cycling of calcium at and near the earth s surface (Zhu and MacDougall 1998 De La Rocha and DePaolo 2000 Schmitt et al. 2003a,b). To understand the record held in deep sea carbonate sediments, it is necessary to document any Ca isotopic fractionation that occurs between dissolved seawater Ca and carbonate shell material. 

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