RECONSTRUCTION OF SEDIMENT RUNOFF FORMATION FEATURES IN THE LAKE KHORLAKEL (NORTH CAUCASUS) CATCHMENT FOR THE LAST 8 THOUSAND YEARS (ACCORDING TO GEOMORPHOLOGICAL AND LITHOSTRATIGRAPHIC DATA)<a href="#FN2"><sup>2</sup></a>

Abstract

The change in sediment yield is an important indicator of the natural environment dynamics, depending on the combination of landscape, tectonic and climatic conditions. Assessment of sediment yield often based on the results of studying the bottom sediments of mountain lakes with relatively compact catchments. However, for correct reconstructions, in addition to analyzing lake sediments, it is necessary to study the causes and mechanizm of sediment redistribution in their catchments, to identify sediment delivery pathways to the reservoir and their possible changes over different time windows. The drainless Lake Khorlakel, located at the altitude of 2045.0 m above sea level on the northern macroslope of the Greater Caucasus. It is a suitable testing ground for complex research: on the one hand, the relict reservoir is an ideal sedimentation trap, and on the other, it is located with in an area of intensive exogenous processes and tectonic activity. The two boreholes were drilled in 2017 in the deepest (≈8 m) part of the lake and 17 samples collected taken from the cores for radiocarbon dating, which made it possible to build an age model for the range from 8000 to 500 yr. BP. Complex geological and geomorphological studies were carried out in 2021 to interpret the obtained data. It was found that sedimentation in the lake is associated with runoff and sediment redistribution in the Elbashi creek catchment. A number of episodes of proluvial activation with the formation of an outflow cone, followed by lake accumulation, have been traced for the last 8 kyr. The connection between lake and catchment ceased only in the last 1 kyr. BP. Two main stages of lake sedimentation with a boundary of 3 kyr. BP and 10 episodes, that are characterized by different proportions of mineral and organic components in bottom sediments were established. Some of the lithostratigraphic boundaries correlate with strong earthquakes that occurred in the Elbrus region, and some – with climatic events.