In any water environment, organic matter undergoes two series of oxidation, hydrolysis and microbial decomposition before entering sediments. The abundance of organic matter in sediments depends on the balance between the amount of organic matter supplied and the amount of destruction. If the amount of supply exceeds the amount of destruction, the abundance will be high and the amount of supply will be small, or close to the balance of destruction, and the organic matter will be less preserved. The deposition rate is high, which is generally conducive to the rapid burial of organic matter in inhibited areas and the preservation of organic matter.
However, higher abundance can be maintained only when the deposition rate increases in proportion to the metabolic rate of organic matter. As a result of anoxic and bacterial activities, sediments rich in organic matter can be found in areas where organic matter can be adequately supplied, appropriate hydrostatic environment and sedimentation of fine mineral particles with moderate sedimentation rate.
Biomarker compounds refer to the organic matter in sediments and those derived from living organisms in crude oil, oil shale and coal. They have a certain stability in the evolution of organic matter, and have little or no change. They basically preserve the carbon skeleton of the original biochemical components and record the special molecular structure information of the original biomass. Therefore, by comparing biological precursors, we can infer their genesis, provide the types and geological ages of biological precursors, indicate the physical and chemical conditions of sedimentary and early diagenetic stages, and provide a variety of information on diagenesis and mineralization.
Organic matter in geological bodies contains two kinds of organic matter with different properties and different quantities. Kerogen is insoluble in organic solvents and soluble organic matter. Kerogen accounts for the vast majority of organic matter in geological bodies (about 95%). Soluble organic matter occupies only about 5_of organic matter. It mainly comes from free molecules of primary hydrocarbons and other lipid compounds in organisms, which constitute biomarkers.
With the continuous updating of identification techniques and methods, a large number of new biomarkers have been identified, and several common biomarkers have been introduced in various biochemical sections of different organisms.
The characteristics and possible evolutionary mechanism of these compounds have been further understood, and the origin of biomarkers has become more and more clear. The above-mentioned factors controlling biological growth can directly affect the amount of organic matter, which is only earlier.