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Ledoyom (Russian:ледоём,IPA:[lʲɪdɐˈjom]) is a term proposed by the Russian geologistVasily Nekhoroshev [ru] forintermontane depressions which might get completely filled byglaciers from the surrounding mountains at the maxima ofglaciation.[1]
The Russian term “Ledoyom (ледоём)” means “body of ice” by analogy with a “body of water” ("vodoyom").[2]
In the 1930s the Russian geologist V.P. Nekhoroshev marked out intermontane depressions in theAltai which might get completely filled by glaciers from the surrounding mountains at the maxima of glaciation. He called such depressions "ledoyoms". Ledoyoms produced large valleyglaciers within outlet runoff valleys from the depressions at culmination stages of their development. Diagnostic marks of the so-called classical ledoyoms aremoraines,eskers andkames on the bottoms of the corresponding depressions.[2]
In the 1980s and 1990s the development of the idea by Russian geologistAlexei Rudoy [ru] ofglacier-dammed lakes which used to fill most of the inter-montane basins of the mountain belt ofSiberia, the depressions ofTeletskoye andBaikal lakes including, took place. It also became clear that many depressions, even very large ones, had been already occupied by dammed water basins by the time when the glaciers of the mountain frame moved forward into them. Thus, mountain glaciers turned into original “shelf” glaciers and armored completely the surface of theglacier-dammed lake joining together floating on the surface. That is the way the so-called “captured lakes” came to exist.
At maximum lowering of thesnow-line (in the Altai and theSayan its depression gave about 1200 m in latepleistocene) some of the lakes (Chuya, Kuray, Uymon and others) began functioning in an under-ice regime because they never got free from ice for thousands of years. Such lakes turned into ice bodies of the “aufeis” type. They consisted of a thick lens of lake water, which was covered by lakeice,aufeis andglacier ice, and bysnow-firn sequence, too. “Aufeis” ledoyoms became independent centers ofglaciation with subradial ice outlets. Possible analogies of such an evolution mechanism and pre-glacial lakes are thick water lenses under a 3–4 kilometer-thick unit of the glacier cover at the sites of Dome B andDome Charlie and theVostok Station in EasternAntarctica.
Thus, depending on the intermontane depression topography, the values, of thesnow-line depression [ru] and of the glaciation energy, the interrelation of the glaciers and the ice-dammed lakes in themountains ofsouth of WesternSiberia could develop according to the following scenarios:
Under different extensions of theglacier at different time periods, one and the same basin could have undergone different sequences of the lake-glacier events.[3]
