The Interaction of Climatic and Tectonic Factors in the Formation of Sediment Runoff in the Holocene in the Khorlakel Lake Catchment (North Caucasus)

Khorlakel Lake is located in the central sector of the Greater Caucasus, on its northern macroslope. The closed lake lies at an altitude of 2045.0 m above sea level on a tectonically determined subhorizontal step with a height of 2020–2100 m a.s.l. associated with the frontal part of the thrust. Two cores were drilled, and 17 samples for radiocarbon dating were taken in 2017 in the deepest (≈8 m) part of the lake, which made it possible to create an age model for the range from 8000 to 500 yr BP. To interpret the stratigraphic–temporal sequence of lacustrine sediments, integrated geological and geomorphological studies in the catchments of the lake and Elbashi Creek and in adjacent territories were conducted. It was established that sedimentation in the lake is associated with the influence of the adjacent Elbashi Creek. A number of episodes of proluvial activation over the last 8500 years with the formation of an proluvial fan have been traced. This was followed by lacustrine sedimentation in a dammed lake, the relic of which is Khorlakel Lake. As a result, sedimentation in Khorlakel Lake and in the adjacent territories is clearly divided into two stages with a partition at ≈3 ka BP with the sedimentation of mainly nonorganic material at the first stage and organic material at the second stage. These stages include ten episodes, which are characterized by different sediments features and varying proportions of mineral and organic components. It was found that the initial lake during the Holocene decreased in size due to the uneven growth of the proluvial fan formed by sediments delivered from the catchment of Elbashi Creek. It has been established that some lithostratigraphic boundaries in the bottom sediments of Khorlakel Lake correlate with known strong earthquakes in the Elbrus region, while other boundaries relate to climatic events in the Central Caucasus that occurred during the Holocene. The complete termination of the connection between the current Khorlakel Lake and the Elbashi Creek catchment occurred in the last ≈1 ka BP.