Ice-marginal deposits near the Umba Town (the south-west of the Kola Peninsula)
Three belts of ice-marginal deposits have been determined in the south-west part of the Kola Peninsula. They correspond to three phases of the Scandinavian Ice Sheet retreat in the Late Pleistocene. Clast fabric analysis and lithological investigation of the glacial deposits and morphometrical analysis of the glacial relief allowed to determine glaciodislocations of squamous-thrust and folded type in the ice-marginal complexes. Arrangement regularities of ice-marginal deposits in the region were defined using morphometrical study of present relief. The squamous-thrust glaciodislocations were found in structure of the first and second belts of the ice-marginal deposits. They correspond to single large ridges or massifs of parallel ridges. Particular fragments represented by low ridges with glaciofolds at their cores formed from loose sediments from the base of the icesheet. The third belt of ice-marginal deposits consists of folded marginal tills and rarely squamous tills interbedding with fluvioglacial deposits. In present relief this belt is represented by ridge-hummocky and hummocky forms and its characteristic feature is deltaic fluvioglacial deposits on the distal end of eskers. Analysis of clast fabric and glaciodislocation structures identified that during the formation of the first and second ridge belts glacier had been moving mainly east along the White Sea Basin. At the time of formation of the third belt active glacier had been advancing south and south-eastwards. Each phase of glacier retreat was accompanied by short-term oscillatory dislocations. In the White Sea Basin and on the moraine plain glacier degradation was fast and had areal character. Frontal type of deglaciation existed on the convergence areas of the ice-marginal complexes. The new data on structure of the glacial deposits, for the first time executed study of structure and clast fabric analysis of glaciodislocations, and morphometrical characteristic of relief allowed to reconstruct dynamic of the last glacier cover on one of the key areas of the Kola region.