Problems of geomorphology at the XXIII International Geographic Congress

Practice of special studies at some regions of the USSR (e. g. Northern Caucasus, Crimea, Aldan Plateau, Transbaikalian area, Far East) showed that magmatic bodies can be used for estimation of the thickness of the layer of denudation. It is necessary also to take into consideration that intrusive bodies with holocrystalline texture can be formed near the Earth's surface, and bodies of prophyritic medium-grained and micrograined texture - quite close to it. Within the studies middle and high mountain regions the lowering of interfluve surface by denudation most often is about few hundred meters, and seldom exceeds one thousand meters.

Shelf is a marginal zone of continents which was transformed' by tectonics during formation of the oceanic basins at Mesozoic-Cenozoic time, its topography and sediments were strongly influenced by marine transgressions and regressions at Pleistocene-Holocene. At present they are modeled by hydrogenic (waves and currents) and gravitational processes. Geological structure, tectonic development, Pleistocene history, present-day topography and sediments reflect processes which acted within the ocean and at land and resulted in creation of the morphostructure of transitional type.

The severest coastal erosion in the USSR occurs along the Black Sea shores in the limits of Georgian SSR. Its main reasons are the decrease of river solid run-off as well as the beach sediments removal for construction purposes. The latter took place thefore the 60 ties. The investigations now carried on and their essential results are described. Much attention has been paid to the budget calculations of beach sediments. Different methods are used. The investigations results are the bases for forecasting The cases of Pitsunda, north Kolkhida, Pcti, Kobuleti and Chorokhi river mouth are dealt with. The long-term survey of shore regime has been organized.

Some data are given on special features of reservoir coast development obtained by laboratory experiments. The technique allows to study stages of the coast development which are difficult to trace at the natural basins. Some data have been obtained on dimensions of shore platform under a certain wave regime. Volumes and mean rates of erosion and accumulation have been estimated.

Detailed studies of sections have revealed that the part of glaciers in topography shaping and accumulation of loose deposits in the Malyk-Sien depression (Upper Kolyma basin) was of little importance, neither features of the depression topography indicate its glacial genesis. The Malyk-Sien depression is considered to be a key region forpaleogeographic studies, therefore the revision of ideas of the deposits origin allows to bring forward. a question of changing views on glacial history of the North-East of the USSR.

Distribution of eolian sands and loess deposits at forested terraces according to the «lee slope rule» can be accounted for by action of prevailing winds which crossed the valleys. The forested terraces orientation, eolian forms pattern and trend of eolian particles size had been correlated with present-day eolian processes and prevailing winds, the comparison revealed .the Middle Volga ancient (Late Pleistocene) eolian mantle being formed by winter winds of the south-western quaters. Thus foci of deflation and sources of loess silt were situated at the lee eroded slopes of river valleys as well as at lake (sea) coasts. The pattern of mantle deposits (which is determined by position of deflation foci and the transition from eolian sands to loess deposits) controls the existing features of soil and landscape conditions within the areas of the deposits.

Relics of planation surface have been established high at the Yuzhno-Muisky Ridge (Stanovoe Highland), they are proved to be fragments of a single exhumed surface of the Late Pre-Cambrian planation.

Cenozoic sediments volume within the Chuya Basin is about 360-800 km², while rock volume removed during formation of 16 main valleys which come into the basin amounts to 3000 km³. Thus 2/3 of the valleys incision belonged to Pre-Cenozoic time, and the subsequent denudation proceeded in the form of erosional deepening of the valleys and their widening with slope processes. The conclusion has been confirmed by analysis of Cenozoic deposits, stages of predominance of a certain group of processes can be identified. There have been recognized two stages of intensive chemical weathering. i. e. Cretaceous and Late Miocene-Early Pliocene. Character of Cenozoic denudation processes was mainly controlled by geomorphic conditions (rugged topography) and climate as well as by slow uplift of the whole Altai.

The paper gives quantitative estimation of shore processes at the Kara Sea coast between 'the Yenisei Gulf and the Vilkitsky Strait and at some islands of the Central Kara Sea. The estimation was based on repeated measuring of distances between geodetic beacons and shore cliffs, with time intervals from 2-3 to 20-30 years, as well as comparing of topographic data of different years. The shore processes at the Kara Sea proved to increase at years with open drift ice and decrease at years with close ice cover.

Up to now there were known six places with residuals of tropic relict karst at the Great Caucasus. The author investigated this type of- karst at three more places of North-Eastern Daghestan. Two places have one karst residual each, at the third place (near the Talga Resort) there are dozens of residuals, their dimensions exceeding those of the analogous forms of the Great Caucasus.

The author develops a concept of residual (conical) karst to be a special morphogenetic type controlled by lithological and structural features and globally distributed. lt can develop within almost all the landscape zones and its morphology reflects zonal features. Within each zone are identified the generations of different age. Therefore from methodical point of view it would be inadequate to consider the residual karst as relict resulted only from tropical environment of ancient epochs. While searching for ore deposits the whole set of zonal landscape attributes should be considered. The author proposes to distinguish notions «zonal karst» (i. e. of moderate humid zone, of tropical zone, of arid zone etc.) from «residual (conical) karst».

Principles of special geomorphic mapping for bauxite search as introduced by V. F. Filatov, Yu. K. Loskutov and G. F. Kuznetsova need more precise definition, particularly of age and genesis of the mapped categories. Besides generate stages of planation and mantle development, it is necessary to determine precise age of denudational topography which is covered with orebearing formations. Therefore it is most important to follow the relations between the denudation relief and its hypergenic mantle formation as well as to specify their genesis.

Geomorphological aspects of the Soviet Program of the International Geodynamic Project