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Residual strength and diameters of lichen Rhizocarpon sp. were measured on different elements of the Late Holocene glacial-cryogenic morphosculpture of frontal parts of glaciers № 29 and 31 in the Suntar-Khayat Range. All in all, 180 lichenometric sites (about 1000 individual measurements of Rhizocarpon sp .) and 150 sites for testing the residual strength of rebound value were organized, on which 380 estimations of this parameter (5674 individual measurements) were performed. For lichenometric index of age (minimal time of exposure) we used statistics RH5 that was a mean value from five maximal individuals on a local site; for index of rebound value Q that was a mean value from 80-100 unit measurements on the same site was taken. Using of data obtained at different times by aerospace surveys made it possible to derive the relationship between the RH5 statistics and time t of the morphosculptures exposure: RH5 = 0.0535 t + 0.29. On the basis of regression coefficients of RH5 and Q indexes the equation RH5 = 69209 e -0,136 Q had been deduced as well as the equation connecting residual strength (rebound value) Q and time t of surface exposure: t = (69209 e -0,136 Qvalue – 0,29)/0,0535. Basing on the equations above, age of the moraine belts of the above glaciers was estimated. The most developed moraine belt, now placed apart from the present-day glacier edges at a distance of 600–700 m, was found to be formed for the whole Little Ice Age. Glaciers reached their maximum volumes during its first phase, i.e. during cold period of 13-15 th centuries. Area of glacierization exceeded its current size by 35–40%. Glaciers remained at their almost steady state until middle of 19 th century and then began to retreat slowly. By middle of 20 th century, glaciers shortened by 5–7%. The most intensive shrinking of these glaciers started in the second half of 20 th century.

This study of glacial-cryogenic complexes of Suntar-Khayata Range is a logical continuation of the research started by M.M. Koreysha in 1957–1959. The studied key site is situated in the upstream of the Burgaly River on the northern slope of Mus-Khaya Mountain (2959 m a.s.l.). It includes glaciers № 29–31 and their ice-cored moraines of different ages. Our study is based on field geomorphologic mapping carried out in 2012, as well as on geospatial analysis of multi-temporal high resolution (1–0.6 m) aerial and satellite imagery. The modern terminus elevation of 16 investigated glaciers varies from 2090 to 2350 m a.s.l. It was found that glaciers’ terminal positions have risen on average from 2052±102 to 2226±114 m a.s.l. after 1945 aerial photography. The termini of Glacier № 29 and Glacier № 31 have retreated approximately by 500–650 m, while the ELA has risen by 61±38 m, from 2346±56 to 2407±55 m a.s.l. The total glaciated area has reduced in size by approximately 36%. The surface of Glacier № 31 has lowered by 50–70 m in its terminal part due to ablation. The estimated glacier shrinkage is valid only for the exposed ice area, since the large amount of glacier ice is buried in ablation moraines, glacier-derived rock glaciers and other glacial-cryogenic landforms. Some ice-cored rock glaciers are 30 to 80 m in thickness. A surface ice flow velocity has decreased 5–6 times compared to the 1957–1959 values. A 45-m-deep geothermal borehole drilled in the middle of Glacier № 31 in 1958–1959 has completely melted away and its mouth shifted 150 m down the glacier surface. The drilling equipment of 1958 is now on the top of a steep 70-m-high rock wall which was entirely covered with ice before 1958. This obviously reflects the magnitude of glacier shrinkage.