In the extent of diploma thesis we analysed the sedimentary core VJ-43 from Lake Vrana in Croatia. Firstly, a sedimentological profile was plotted and the latter proved that the core consists of an alternation of thin layers and laminates of the sediment with thickness of 1.0 cm to 10.5 cm. The sediment consisted of sandy silt and silt, the first being the prevalent one when it came to proportion. Additionally, four units with snails were observed in the lower part of the core.
XRF results proved that the elements silicon, aluminum, iron and potassium have significantly higher proportions (%) at depth intervals of 0.5-60 cm (A3), 100-150 cm (A2) and 185-225 cm (A1). We conclude that the positive anomalies A3, A2 and A1 are a reflection of a larger share of the terrigenous component. The proportions of calcium and magnesium show a trend of lower values or a negative anomaly A3 in the depth range of 0.5 cm to 60 cm. We conclude that they are bounded to the carbonate minerals and that they are of autigenic origin. The elements zirconium, rubidium, lead, zinc, iron, titanium, potassium and sulfur have significantly higher values (ppm) at depth intervals of 0.5-60 cm (A3), 100-150 cm (A2) and 185-225 cm (A1). Positive anomalies A3, A2 and A1 are attributed to the greater contribution of the terrigenous component (Zr, Rb, K) and the anthropogenic impact (Pb, Zn, Ti, S). The elements nickel and manganese show a declining trend at depths of 0.5 cm to 16 cm. They are connected by overlapping low values at similar depths of 16, 121 and 133 cm. We assume that they may be bounded to organic matter. Molybdenum shows inverse correlations with nickel and manganese with high values at depths of 16, 121 and 133 cm, and we assume that molybdenum may be bounded to organic complexes. Strontium has lower values or. negative anomaly A3 at a depth interval of 0.5–60 cm and we conclude that it is bounded to carbonates.
The measurements of the XRD analysis have shown the sediment composition by the minerals, such as calcite, aragonite and quartz. The proportion of calcite and quartz decreased with depth by up to 80 cm whereas the proportion of aragonite increased. Based on the correspondence of the calcium negative anomaly A3 and the trend of varying the proportion of calcite by the depths, we conclude that calcite is mostly of autogenous origin. The increased proportion of aragonite in depth can be attributed to the presence of snail shells. Quartz was, in terms of samples, present only in small proportions and its origin is likely terrigenous.
Using the Bayesian age model, we estimated the age of the sediment core VJ-38 at a depth of 9 cm to 44.1 years and the sedimentation rate at 0.204 cm per year. According to the estimated age, the A3 anomaly at the depth interval of 0.5-60 cm is associated with the melioration and construction of the Prosika canal. We were unable to associate the A2 and A3 anomalies at depth intervals of 100–150 cm and 185–255 cm with the aforementioned interventions in the natural surroundings.
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