Matter sapropel organic

Spiker, E. C. and Hatcher, P. G. (1984). Carbon isotop>e fractionation of sapropelic organic matter during early diagenesis Org. Geochem. 5, 283-290. 

Bouloubassi, I., Rullkotter, J. and Meyers, P.A., 1999. Origin and transformation of organic matter in Pliocene-Pleistocene Mediterranean sapropels Organic geochemical evidence reviewed. Mar. Geol. 153 177-199. 

In addition to time, the quantity of gaseous hydrocarbons formed varies with the type of organic source material, which can be broadly classified as sapropelic (marine) or humic (terrestrial). As shown in Fig. 5-1, considerably more C2-C4 and other oil-type hydrocarbons are generated from sapropelic sources than from humic sources. In addition to the different volumes and types of petroleum (oil versus gas) produced from the two source materials, their carbon isotope compositions are different terrestrial organic matter is reported to have lower C concentrations than marine organisms (Galimov, 1968 Silverman and Epstein, 1958). 

The abundant and ubiquitous organic matter in the Phosphoria sea may have been produced in a way similar to that in Walvis Bay on the southwest African coast, which Brongersma-Sanders (19) explained by the relationship of upwelling, large biomass production, and the accumulation of biological remains on the sea floor as sapropelic ooze. 

An example of this selective preservation is shown in Figure 6 with the NMR spectra of the algal sapropel from a near-surface and a 2.8 m interval. In the surface layers, the organic-rich sapropel is dominated by polysaccharides denoted by peaks at 72 and 106 ppm in the spectrum, and humin accounts for less than 20% of the organic matter. At depth, the polysaccharides and other labile substances are decomposed, and the sapropel contains mostly paraffinic macromolecular humin (approximately 70% of the organic matter). Hatcher et al. (1983b) have shown that the loss of labile... 

It is important to note that under the anaerobic conditions existing in the sapropel negligible amounts of humic acids are present. The humic acids that do exist account for less than 5% of the organic matter and are structurally unrelated to the humin. They are essentially polyuronic acids and are only called humic acids because they are operationally extracted as such (Hatcher et al., 1983b). Thus, it is unlikely that humic acids are intermediates in the formation of humin in this environment. Selective preservation is the simplest explanation for the existence of humin. 

Humic isolates from different layers of an organic matter rich algal sapropel from Mangrove Lake, Bermuda, have been analyzed using solid-state N NMR in order to reveal chemical structural interrelationships that allow delineation of diagenetic pathways. ... 

In the fossil record, dark-colored organic-matter-rich layers (black shales, sapropels, petrolenm sonrce rocks in general) witness periods of time when conditions for organic matter accnmnlation in sediments apparently were particnlarly favorable. As the other extreme, massive seqnences of white- or red-colored sedimentary rocks are devoid of organic matter. Althongh these rocks may contain abundant calcareons or siliceons plankton fossils, the organic matter of the organisms apparently was destroyed before it conld be bnried in the sediments. 

The Silurian and Early Devonian organic matter is typically sapropelic, mixed, and humic (Fig. 5.3). It was intensely generating hydrocarbons in the south of the region in the Paleozoic, and in the areas of the other basins in the Mesozoic. At present, the organic matter may presumably persist either at the end of the oil window, or in the gas window and low-molecular hydrocarbons. The radioactive shales of the Early Silurian are good source rocks in the central and north-eastern areas of the region. The Late Devonian and Carboniferous periods have provided satisfactory source rocks in the south-west and north-east of the region. 

Higher temperatures are characteristic of the sedimentary section of the Akfadou area as compared to the Takhoukht area. Temperatures of about 120 °C were reached in Early Devonian sediments. Our model calculations for the end of the Early Carboniferous (about 330 Ma), and before the Hercynian uplift and erosion, give temperatures and maturation levels for the Ordovician, Silurian, and Early Devonian shales consistent with early to main stages of hydrocarbon generation (Table 6.6). Toward the close of the Carboniferous (about 289 Ma), the sapropelic and humic organic matter of the Ordovician, Silurian, and probably Devonian source shales was sufficiently mature to generate both liquid and gaseous hydrocarbons. Silurian and Devonian shales in other areas of the basin are also characterized by considerable potential... 

Passier H. F., Bottcher M. E. and DeLange G. J. (1999) Sulphur enrichment in organic matter of Eastern Mediterranean sapropel a study of sulphur isotope partition. A uaL Geochem. 5, 99-118. 

The concentrations of TOC and IC are depicted in Fig. 1. An increase of TOC up to 3% is observed between 43 and 41 cm followed by a short decrease before TOC stabilizes around 3%. The top part of the sapropel, 35-33 cm, exhibits a decrease in TOC to values below 1%. This may be explained by a true decrease in the amount of deposited organic carbon and/or oxidation of organic matter after deposition. Post-depositional oxidation has been reported for several sapropels and in some cases all organic carbon have been oxidized (e.g. Thomson et al, 1995 Jung et al, 1997). As the colors of the core are black and gray they do not indicate any substantial oxidation. Mn concentrations only show a slight increase at the top of the... 

As a first approach a model was used to test whether anoxic deep water can be the sole explanation to the high concentrations of organic matter in the sapropel layers. Data from the literature has been combined to make an algorithm using Model Maker ver. 3 software. The model uses the present primary productivity of 40 mg 10 mg C day This is an average of the 12 g C given by Bethoux (1989) and 16.7 g C m a by Krom et al (1992). 

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