In the thesis, we studied the sediment core SI5A taken in the area of barchan dunes
in the Gulf of Trieste. The purpose of the work was to identify the sediment and to
determine their structure, texture and composition. We also tried to determine
sediment provinence and the process of formation of barchan dunes. The core SI5A
was sedimentologically recorded. Sixteen samples were taken from the profile. These
samples were then analysed with granulometric and XRD analysis. Five petrographic
thin sections were prepared for examination with an optical light microscope. Granulometric analysis showed that the proportion of the sand fraction is the highest in all samples. Most of the samples are classified as slightly clayey silty sand. The distribution curves are polymodal for all samples, indicating the presence of different grain populations. The mineral composition of sediments was determined with XRD analysis. It showed that dolomite and calcite are most common minerals in all samples. These are followed by quartz, aragonite, albite and halite. The content of dolomite and calcite is increasing with depth, while the proportion of quartz decreases with depth. The proportion of aragonite is related to presence of shell fragments, while halite and albite are fairly distributed throughout the core. Microscopic description of petrographic thin sections showed that the sediment is moderately to well sorted and that all samples are most abundant in subrounded to rounded carbonate grains. Four samples were classified as quartz-carbonate lithogenic silty sand, and the deepest sample as quartz-carbonate lithogenic sand. The results show that barchan dunes are composed of resedimented LGM (Last Glacial Maximum) sediments from northern Adriatic Sea and sediments from Slovenian flysh coast. These sediments were then resedimented in marine environment by currents directed towards northeast into barchan dunes.
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