As a part of the research work, two cores of Krn Lake sediments, 73 and 92 cm deep, were analysed. Detailed sedimentological profiles were made for both cores and samples for granulometric analysis were taken. For one core, samples for dating were taken by using radionuclides 210Pb and 226Ra.
Sedimentological profiles show that both cores consist of thin-layered and laminated sediments. They are composed of clay, clayey silt, silt, sandy silt and sand of gray, sometimes slightly greenish and brownish colour. Sediment is in some layers and in laminae normally graded. Inside some of the laminae in both cores, remains of organic material and individual dropstonescan be found.
The results of granulometric analysis showed that the silt strongly dominates in both cores, with slightly more sand in the first and slightly more clay in the second core.
In the core KRN01, 20 of the 50 samples represent clayey silty sand, and the other 30 clayey sandy silt. Most sand occurs at a depth of 11 cm, 88% of the sample, silt at a depth of 67.5 cm with 83% and clay at a depth of 43 cm with 7.4% of the sample.
In the core KRN09, seven samples represent clayey silty sand, one sample silty clay, and other 62 samples clayey sandy silt. Most sand occurs at a depth of 2.5 cm, 66% of the sample, silt at a depth of 57.5 cm with 86.9% and clay at a depth of 44 cm with 76.5% of the sample.
For the core KRN09W, sediment dating was performed by using radionuclides 210Pb and 226Ra. The results showed that sedimentation rate was 0,072 cm± 0,005 cm per year, meaning that the core at the depth of 93 cm is ~ 1292 years old.
Based on a detailed profile of the cores, sediment structure, sediment textures, and CM interpretation diagrams (Passega 1964), I conclude that most sediments were formed by gravitational (most likely turbidite) flows. Only a small portion of the sediment (mainly in the KRN09 core) was deposited with predominant pelagic sedimentation. The sediments of Lake Krn are also characterized by a high content of macroscopically noticeable organic matter (organic debris). Based on the macroscopic observations, I find that these are mostly remnants of higher terrestrial plants. This organic material, along with a sediment, was washed into the lake from the shores of the lake and from the lake district.
Based on a determined average age of lake sediments, coarse-grained sediment could settle at a depth of 0-1 cm as a result of the earthquakes, which happened in 1998 and 2004, and as a result of high rainfall, such as the one that occurred in November 2000. Sediment at a depth of 4.5-5.5 could be partly attributed to the earthquakes of 1942 and 1944.
There is also a marked difference in sedimentation in different parts of the lake. The bottom of the lake consists of two depressions, which are separated by a ridge. In the depression that is proximal to the delta (core KRN01), a coarser-grained fraction is sedimented than in the distal depression on the northeast side of the lake (core KRN09). These different sedimentation conditions also preclude a direct lateral correlation of the two cores.
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