ИСТИНА

Glaciation lobes entering the river valleys can block the outflow and cause the formation of ice-dammed (or proglacial) lakes. Such lakes occupied the river valleys during the glaciations and their outline usually repeated the river drainage pattern. The proglacial lake evidences are usually represented by “varved clays” i.e. laminated silts or clays alternating with sands deposited in the deep water sedimentary environment, and shoreline which mostly is not well preserved. The river Severnaya Dvina catchment basin occupying the vast area in the European North-East affected the influence of Scandinavian Ice Sheet during the Quaternary and thus the proglacial lakes could develop within the valleys of SD river and its large tributaries Vychegda, Sukhona and Vaga. The main goal of this study was to analyze a variety of the Late Pleistocene ice-dammed lake reconstructions in the SD river basin and the results of our field observations of their sediments and pattern. We can identify one episode of proglacial lake formation in the Late Pleistocene within the Severnaya Dvina catchment area. Two separate lake systems formed during the LGM (~ca 20 kyr BP): the Severnaya Dvina rather small, short-lived and shallow lake occupying only the middle reaches of SD river valley, and large, deep, long-living and braided Vaga lake occupying the valleys of Vaga and its tributaries Kuloi and Kokshen’ga. Such a difference in lake configuration and history could be explained by morphological features of river valleys, runoff volume and position of glacioisostatic forebulge crossing these river systems. The absolute height of water level could reach 80 m a.s.l.