The variation of the continental ice shield and the amount of ice in the ocean strongly influences the development of below-sea level deposits off the west coast of the Antarctic Peninsula. The variation of the ice shield and the amount of ice in the ocean has an impact on the global climate.
Core-depth drillings can be used to backtrack these variations over periods of several millions years. Particle size analysis helps significantly.
The particle distribution of the obtained material is a substantial parameter, which is determined during sediment analysis. This article outlines an extensive procedure, where the share of a particle size smaller than 63 µm is attained and prepared for particle size determination.
Figure 1. Preparation path for the examination of the fine share of sediment material
Nanoparticle Size Analysis
An ANALYSETTE 22 was used to analyze the obtained material, and the results were evaluated in a number of different ways. Examples shown here are the contour-plots of the fine share against the drilling depth and the age of the sediment respectively, like it was received from magnetic examinations. In each case, the share larger than 63 µm is also shown in a separate column.
Figure 2 illustrates the contour-plot of the particle size distribution. The particle size distribution for the sample material from different drilling depths was divided into six size classes and color-coded.
Figure 2A. Applied against the drilling depth in 1 m intervals.
Figure 2B. Applied against the data obtained from magnetic measuring age of the sediments in steps of 20 years each. Recognizable are several intervals, in which the cyclicity and the relation of clay/silt vary.
The distribution momentums can be obtained from the measured distributions. The distribution momentums are statistical values and characterize the distributions in a brief, concise form.
The standard deviation of the distribution is an example of this type of value. The standard deviation of the distribution is a dimension for its width, or the 'skewness.' The skewness reveals if a distribution is symmetrical (skewness= 0), has a greater amount of coarse area (skewness >0), or the fine area (skewness <0).
Figure 3 shows that several of these statistical parameters are applied against the drilling depth and also against the age of the sediment. However, here the fine share smaller than 10 µm was initially removed, because the share between 10 and 63 µm delivers significant information regarding the deposit processes.
As the suppression of the fine share is smaller than 10 µm compared to the overall distribution, there is a change in the obtained results.
Figure 3. Moments of the distribution applied against depth and age, respectively. Only the share of the sediment with grain sizes in the range of 10-63 µm is considered here.
When applying the obtained skewness of all measured distributions against the mean value of the particle size, and then against the standard deviation of the distribution, it clearly shows that there are three populations which can be matched to different depositing processes of the sediments (Figure 4).
Figure 4. Skewness of the distribution applied against the median value and the standard deviation of the distribution, respectively. Three different populations are clearly recognizable.
Figure 5 shows the data obtained from viewing the individual populations. Detailed conclusions can be drawn from these diagrams regarding the chronological order of the depositing processes. These processes provide important information about factors influencing them, such as the median temperature.
Figure 5. Distribution of the single population applied over the drilling depth and the age of the sediments, respectively. Each population is color-coded, and the amplitudes show the medium grain size. The black curves represent the share of the respective population in 10 m intervals.
This information has been sourced, reviewed and adapted from materials provided by FRITSCH GMBH - Milling and Sizing.
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