Diagenesis defined

Unquestionably, there are limitations to such a procedure, and because calculations for two specimens failed, they lead to an even higher deviation from the control signal. These limits have to be defined by future work. The model experiment is only an approach to collagen diagenesis in buried bone. In nature, more than one bacterial species feeds from bone protein, and a... 

In order to determine the source composition of sediments using trace elements, it is necessary to ascertain that the element is immobile under conditions of diagenesis and weathering (Spalletti 2008). Several ratios and plots may be used to define the source rocks. The felsic source rock compositions are found in the Co/Th vs. La/Sc diagram (Fig. 3 Table 1). Other trace element characteristics of sedimentary rocks also place some constrains on the nature of the source rock. Floyd Leveridge (1987) used a La/Sc vs. Hf plot to discriminate between different source compositions. In this plot, most data fall in the felsic source to mixed felsic/basic source field (Fig. 4 Table 1). 

Early diagenesis is defined as the changes occurring during burial to a few hundred meters where elevated temperatures are not encountered and uplift above sea level does not occur. 

Between Ca 50 °C and 300 °C, sandstones and mudrocks ( shales ) undergo massive chemical and textural reorganization. In this temperature interval detrital grains, and the rock textures defined by grains, are lost by reactions with pore fluids. Chemical and physical processes in late diagenesis transform sUiciclastic sediments into rocks. Predictive models of porosity evolution with depth depend upon an understanding of these processes. Because the magnitude of... 

The fact that the relative presence of alkane and cyc/o-alkane hydrocarbons in naphtha fractions is so similar suggests that the most of the oil has undergone the same sequence of reactions or diagenesis. The difference in the naphtha volume fraction inside the oil as well as the larger difference in the aromatic components, however, may indicate the extent to which the diagenesis has proceeded. This is why it is important to define the PONA index, i.e. the relative amount of paraffins, olefins, naphthenes and aromatics, so that the relative sizes... 

The role of the benthic interface is not to be defined exclusively by one transport direction. On the one hand, deposition and burial of marine sediments remove elements from the marine cycles over geological time periods. Yet, as the example of the carbon cycle shown above already demonstrated, an immense proportion of accumulated particles are subject to dissolution or microbial decomposition in the course of early diagenesis (cf. Chapter 9). Marine sediments therefore also act as a secondary source of remineralized dissolved components. The coexistence of these two fundamental, but oppositely directed mass movements constitutes one of the most essential phenomena at the seafloor. Next to studies on particle fluxes through the water column and element-specific accumulation rates, the quantification of benthic flux rates across the sediment/ water boundary represents the third pre-condition for obtaining a complete balance of the marine material cycles. 

When the diagenesis is isochemical at a scale of 1-lOm, the compaction and shortening (AZ) of a sedimentary sequence (Z) is equal to the porosity loss (A tp ) due to quartz cementation. The reduction in stratigraphic thickness is defined by ... 

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