Fossil deposits

There are some exceptions. The diatoms are unicellular microorganisms that protect themselves with a filigree skeleton of silicon dioxide (silicic acid). The sometimes major fossil deposits of kieselguhr (diatomaceous earth or diatomite)... 

Diluents, sometimes known as inerts or carriers, play an important role in the behavior of the formulated product. Diluents have been prepared from agricultural wastes such as walnut shells, pecan shells, tobacco stems, and corncobs from minerals such as kaolinite, attapulgite, and talc and from fossilized deposits such as diatom beds. The exact diluent used in a given preparation depends on cost, properties, and availability. Dusts require low sorptive inerts to minimize the toxicant-diluent interaction. For WPs, inerts must be high in sorptive power because they carry a large amount of toxicant especially when the toxicant is a liquid. Otherwise, the formulated product would be likely to cake badly in storage. It is required that a diluent must be truly inert. However, formulators often find that an inert diluent contains hot spots or alkalinity to inactivate part of the toxicant. In this case, urea can be used as a deactivator to counteract the undesirable effects in some dust and wettable formulations (Terriere, 1982). 

Because aragonite is more susceptible to dissolution than calcite, especially under the influence of meteoric waters, and because most fossil corals are recovered from uplifted terrestrial deposits, diagenesis is an especially important limiting factor in recovering older coral records. This problem can be circumvented by drilling into submerged fossil deposits, but because of logistical difficulties, so far this has been accomplished in only a few key spots such as Barbados and Tahiti (Eairbanks, 1989 Bard et al., 1996). 

Fig. 5.15. Structures resembling Metallogenium personatum in fossil deposits, (a), manganese-containing structures in the Cooley Dolomite of the McArthur Group, N.T., Australia (from Muir et al., 1974) (b) as in (a) (unpublished photograph by M.D. Muir) (c) structures from minor iron formations in the McMinn Formation of the Roper Group, N.T., Australia (unpublished photograph by C.J. Peat and M.D. Muir). Bar = 10 pm.

Similar considerations for ancient metal(loid) uptake or transformations appear quite reasonable for primordial microflora, especially the algae which account for the present ubiquitous distribution of kerogen in shale rocks. (9,10) In general, the fossil deposition record suggests that substantial metal(loid) accumulation also occurred in higher plants which underwent diagenesis to form modern petroleum and coal deposits. (11,12) In many instances, various present-day species of plants are known to both selectively and extensively hyperaccumulate various metal(loid)s... 

The molecular forms of trace metal(loid)s in fossil deposits is doubtless complex, probably consisting of varying proportions of inorganic, metallo-organic (no covalent element-carbon bonds), and true organometallic chemical species residing in unspecified... 

As diatoms are one of the major groups of algae in the oceans, large fossil deposits of diatom walls have accumulated in many areas. These deposits are known as diatomaceous earth. 

Bogdanov, Ju.A., Lisitsyn, A.P. and Romankevitsh, E.A., 1971. Organic matter of particles and bottom deposits of seas and oceans. In N.V. Vassoevitsh (Editor), Organic Matter of Recent and Fossil Deposits. Nauka, Moscow, pp. 35—103 (in Russian). 

For thousands of years before mid-ocean ridge hot springs were discovered in the oceans, people mined copper from mineral deposits that were originally formed on oceanic spreading ridges. These fossil deposits are embedded in old fragments of seafloor called ophiolites that have been uplifted and emplaced onto land by fault movements. The copper-rich mineral deposits in the Troodos ophiolite of Cyprus are well-known examples of fossil ocean-ridge deposits that have been mined for at least 2500 years in fact, the word copper is derived from the Latin word cyprium which means from Cyprus. ... 

Autochthonous 1) Rocks, sediments or deposits formed and deposited at the same place as where they are found today fossils deposited at the place where the animal lived or the plant grew. 2) A material (e.g., rock, mineral, fossil) formed in the basin or water body where it is found (cf. allochthonous). 

Hydrocarbons derived from crude oil and other fossil deposits are separated into their various fractions by using distillation and so it is not surprising that distillation is used as an analytical tool to characterize them. Table 4 list examples of applications of distillation to hydrocarbon characterization including bituminous materials, tars, fuels, and derived organic materials. 

Pinaceae, usually are diterpenes with a 5a,10p-configura-tion. Many plants serve as commerical sources of resins the genera Hymenaea and Copaifera (Fabaceae) and Pinus and Agatha (gymnosperms) are probably the best known producers. Resins are used as feedstocks for products such as insecticides, incense, varnishes, rosin, and adhesives, and as components of drugs and polishes. Fossilized deposits of diterpenes are known as amber (Langenheim, 1990). 

Since 1973, with the petroleum crisis, it has been fully demonstrated that a search for more reliable, renewable and economical sources of new materials was needed as an answer to the ever-growing demand of the modern, highly technological world. This has led man to the origin of the large fossil deposits of raw materials, especially to the plants. 

While there are more lines of palaeontological evidence for the origin of neotropical savannas, they do not produce an entirely clear picture, especially for the Brazilian cerrados, partly because it seems that virtually none of the fossil deposits (reviewed by Jacobs et al. [1999]) come from this area. It seems that neotropical savanna is unlikely to be older than the mid-Miocene, but the South American herbivore fossil evidence does not rule out an Oligocene origin. Nevertheless,... 

As mentioned, enantiomers rotate plane-polarized light by equal amounts but in opposite directions. Thus, in 2-bromobutane the (-) enantiomer rotates this plane counterclockwise by 23.1°, its mirror image (+)-2-bromobutane clockwise by 23.1°. It follows that a 1 1 mixture of (+) and ( ) enantiomers shows no rotation and is therefore optically inactive. Snch a mixture is called a racemic mixture. If one enantiomer equilibrates with its nurror image, it is said to undergo racemization. For example, amino acids such as (+)-alanine (Table 5-1) have been found to undergo very slow racemization in fossil deposits, resulting in reduced optical activity. 

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