Sedimentary organic matter

Several conditions need to be satisfied for the existence of a hydrocarbon accumulation, as indicated in Figure 2.1. The first of these is an area in which a suitable sequence of rocks has accumulated over geologic time, the sedimentary basin. Within that sequence there needs to be a high content of organic matter, the source rock. Through elevated temperatures and pressures these rocks must have reached maturation, the condition at which hydrocarbons are expelled from the source rock. 

Oil Shale. Oil shale (qv) is a sedimentary rock that contains organic matter, referred to as kerogen, and another natural resource of some consequence that could be exploited as a source of synthetic natural gas (67—69). However, as of this writing, oil shale has found Htde use as a source of substitute natural gas. 

This removal may also include diffusion of soluble U(VI) from seawater into the sediment via pore water. Uranium-organic matter complexes are also prevalent in the marine environment. Organically bound uranium was found to make up to 20% of the dissolved U concentration in the open ocean." ° Uranium may also be enriched in estuarine colloids and in suspended organic matter within the surface ocean. " Scott" and Maeda and Windom" have suggested the possibility that humic acids can efficiently scavenge uranium in low salinity regions of some estuaries. Finally, sedimentary organic matter can also efficiently complex or adsorb uranium and other radionuclides. 

Hedges, J. and Keil, R. (1995). Sedimentary organic matter preservation an assessment and speculative synthesis, Marine Chem. 49, 81-115. 

The general PLC approach described in the preceding text can be modified when the research aim is to investigate one selected compound (or a group of compounds), or in the case of some less common samples, such as highly biodegraded or hydro-thermal petroleum, tars, immature sedimentary organic matter, or even products of biomass combustion [70,86,87]. 

Aquifer sediments in the model are confined by and interleaved with fine-grained sediments that contain sedimentary organic matter. The organic matter decays gradually by microbial fermentation and anaerobic oxidation,... 

Nuwer, J.M. Keil, R.G., 2005. Sedimentary organic matter geochemistry of Clayoquot Sound, Vancouver Island, British Columbia. Limnology and Oceanography 50, 1119— 1128. 

The evolution of sedimentary organic matter (OM) under the influence of increasing burial depth and related temperature rise is termed maturation and this process is commonly subdivided into three stages, i.e., diagenegisis, catagenesis, and metagenesis (Figure 1). 

Dean WE, Jr. Determination of carbonate and organic matter in calcareous sediments and sedimentary rocks by loss on ignition-comparison with other methods. J. Sediment. Petrol. 1974 44 242-248. 

Oxygen 18o/16o 160 = 99.759 170 = 0.037 lsO = 0.204 Water, biomineralized carbonates and phosphates, sedimentary phosphates and carbonates, silicates, organic matter Climate, plant and animal water metabolism, ocean temperature, provenance (marble), chronostratigraphy... 

Sediment deposition on the seafloor traps interstitial water. After deposition, complex reactions take place in the sediment, most of them fueled by the decay of organic matter, such as sulfate reduction, denitrification,... Because of fast diffusion rates of most cations in seawater, the presence of interstitial water makes exchange between overlying sedimentary layers a much easier process than if sediment deposition was dry. The book by Berner (1980) is entirely dedicated to these processes and only a short example is given here. 

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