Sediments calcareous, formation

In the preceding sections, we have discussed the marine processes that control calcium carbonate s formation, dissolution, and delivery to the seafloor. Their combined effects determine the geographic distribution of calcium carbonate in marine sediments seen in Figure 15.5. As noted earlier, the global distribution of calcareous sediments does not seem to follow that of plankton production. This points to the overriding importance of the processes that control the dissolution and sedimentation of calcium carbonate. 

Wall and Dale 1968). Sarjeant (1974) has summarised information on living and fossil dinoflagellates, and calcareous cyst formation. Calcification seems to follow a matrix controlled pattern. The contribution of dinoflagellates to the formation of carbonate sediments and rocks seems to be of minor importance. 

Johnson, M.R. (1989) Paleogeographic significance of oriented calcareous concretions in the Triassic Katberg Formation, South Africa. J. sediment. Petrol., 59, 1008-1010. 

This section primarily focuses on the description of the deposition and accumulation of carbonates in shallow waters and in the deep ocean. The main depocenters for calcium carbonates are the continental shelf areas, as well as island arcs or atolls, which are the typical shallow water environments for massive carbonate formation, and the pelagic deep-sea sediments above the calcite compensation depth catching the rain of small calcareous tests formed by marine plankton in the surface waters. 

Ferry J.M., 1983, Mineral reactions and element migration during metamorphism of calcareous sediments from the Vasselboro Formation, south-central Maine. Amer. Mineral., 68, 334-354. 

Processes (2.115) and (2.116) describe the solid-liquid equilibrium at the oceanic bottom (sediment-seawater interface) with suspended matter in seawater (calcareous organisms). Moreover, similarly the processes of heterogeneous nucleation and droplet formation from CCN as well as in general the solid-water interfacial process are described (Fig. 2.93). Hence, seawater is an excellent solvent for acidic gases such as SO2 (used for flue-gas desulfurization at some coastal site power stations) and atmospheric CO2. The ratio between atmospheric and oceanic (water dissolved) CO2 is described by the Henry equilibrium (2.117 see also Chapter 4.3.2) ... 

Schmidt and Ford (1969) mentioned that a thin layer of marble in the Mt. Walcott Formation contains stromatolites. However, Storey and Macdonald (1987) and Pankhurst et al. (1988) later stated that these stro-matohtes are actually composed of interlaminated calcareous siltstone and limestone that underwent soft-sediment deformation. The same authors did find abundant echinoderm plates and sponge spicules similar to Protospongia fenestrata which occurs in the Middle Cambrian Nelson Limestone of the Pensacola Mountains (Weber and Fedorov 1980, 1981). The Mt. Walcott Formation also contains trace fossils (Planolites and Chondrites). Although Planolites has been found in rocks that are 1,000 milhon years old, the earhest appearance of Chondrites is in rocks of Cambrian age. Therefore, Pankhurst et al. (1988) concluded that the paleontological evidence supports a Phanerozoic age for the Mt. Walcott Formation, whereas Schmidt and Ford (1969) had previonsly assigned it a probable Neoproterozoic age. 

Maximum outlet temperatures for cooling water are usually dictated by the chemistry of the cooling water. Most cooling waters contain chlorides and carbonates consequently heat transfer surfaces (tube wall) temperatures must not exceed certain values in order to minimize formation of calcareous deposits, or scaling, which reduces heat transfer and leads to excessive corrosion. In addition, velocity restriction must be imposed and observed to prevent corrosion and fouling as a result of sedimentation and poor venting. Stagnant conditions on the water side must always be avoided. In some plants water consumption is dictated by thermal pollution restrictions. 

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