Sedimentation Rates Evaluation in Caucasus Mountain Lakes as Indicators of Their Catchments Denudation

Abstract

The sedimentation rates of five lakes in the Western and Central Caucasus in the late Holocene were studied on the basis of radioisotope dating (137Cs of global and Chernobyl origin, 210Pbex, 14C). The lakes are located in different landscape zones and has different origin. The selection of bottom sediment cores was carried out after a reservoir map of the depths моnitoring based in areas with average maximum depths. The studied lakes catchments are minimally affected by anthropogenic impact; therefore, the reservoir influx of sediments, the sedimentation rate and their changes over time are mainly controlled by natural factors. It has been established that for two lakes in the mid-mountains with tinned and forested catchments, the current sediment accumulation rate is 0.05–0.07 cm/year, and half of it consist organic matter. Sedimentation rates in the high-mountain Donguz-Orun Lake increases and have been equal to 0.32 cm/year in the last 30 years without taking into account the significant amount of sediment that is redeposited in the front of the reservoir delta. The opposite trend of sedimentation rates was revealed for the high-mountain Garabashi Lake, the distinctive feature of which is the absence of glaciers at present and a rather high projective cover of vegetation catchment. Sedimentation rates in the coastal Sukhoi Liman Lake, located in the low-mountain zone, are 0.1 cm/year with a slight growth trend due to some increase in anthropogenic load associated with local clearcuts and an increase in recreational load.