4
Organic Matter: The Driving Force for Early Diagenesis
158
4.5
Analytical Techniques
Organic geochemical analyses of marine sediments may range from the rapid determination of a
few bulk parameters to a high level of sophistication if trace organic constituents are to be
investigated at the molecular level. The analytical
scheme in Figure 4.21 is one of many that are
currently being used in different laboratories. It is
certainly not complete nor is it fully applied to
each sample, particularly not when large series are
studied. For example, the analysis of amino acids
(e.g. Mitterer 1993), sugars (Cowie and Hedges
1984; Moers et al. 1993), lignin (Goñi and Hedges
1992), or humic substances (Brüchert 1998; Senesi
and Miano 1994; Rashid 1985) requires a modification of the scheme in Figure 4.21. Other than in
inorganic geochemical analysis, where modern
instrumentation allows the simultaneous determination of a wide range of element concentrations,
the millions of possible organic compounds
require an a priori selectivity, but even the analysis of selected lipids can be quite time-consuming.
In addition, the amount of sample material
required for molecular organic geochemical
studies is higher than for many other types of
analyses, and this limits stratigraphic (time)
resolution.
4.5.1
Sample Requirements
Most organic geochemical methods require a well
homogenized, pulverized sample aliquot. An exception
is reflected-light microscopy in organic petrography
where the association of organic matter with the
sediment matrix can be quite informative and is,
therefore, preserved. Before homogenization, the
sample needs drying either at ambient temperature or
by freeze-drying. Higher temperatures are to be avoided
due to the thermal lability of the organic matter. For the
same reason, sediments – particularly those of young
Fig. 4.21
Example of an analytical scheme of organic geochemical analyses of marine sediments comprising bulk and
molecular parameters.
Organic Matter: The Driving Force for Early Diagenesis
158
4.5
Analytical Techniques
Organic geochemical analyses of marine sediments may range from the rapid determination of a
few bulk parameters to a high level of sophistication if trace organic constituents are to be
investigated at the molecular level. The analytical
scheme in Figure 4.21 is one of many that are
currently being used in different laboratories. It is
certainly not complete nor is it fully applied to
each sample, particularly not when large series are
studied. For example, the analysis of amino acids
(e.g. Mitterer 1993), sugars (Cowie and Hedges
1984; Moers et al. 1993), lignin (Goñi and Hedges
1992), or humic substances (Brüchert 1998; Senesi
and Miano 1994; Rashid 1985) requires a modification of the scheme in Figure 4.21. Other than in
inorganic geochemical analysis, where modern
instrumentation allows the simultaneous determination of a wide range of element concentrations,
the millions of possible organic compounds
require an a priori selectivity, but even the analysis of selected lipids can be quite time-consuming.
In addition, the amount of sample material
required for molecular organic geochemical
studies is higher than for many other types of
analyses, and this limits stratigraphic (time)
resolution.
4.5.1
Sample Requirements
Most organic geochemical methods require a well
homogenized, pulverized sample aliquot. An exception
is reflected-light microscopy in organic petrography
where the association of organic matter with the
sediment matrix can be quite informative and is,
therefore, preserved. Before homogenization, the
sample needs drying either at ambient temperature or
by freeze-drying. Higher temperatures are to be avoided
due to the thermal lability of the organic matter. For the
same reason, sediments – particularly those of young
Fig. 4.21
Example of an analytical scheme of organic geochemical analyses of marine sediments comprising bulk and
molecular parameters.