Beschreibung: The last glacial maximum (LGM) of the Scandinavian ice sheet in the Arkhangelsk region has been identified morphologically as ridges and hummocks in an otherwise flat topography. Stratigraphically the limit is marked by the presence of till above Mikhulinian (last interglacial) sediments inside the ridges and by the absence of till outside the ridges. During the LGM, ice flowed into the region from the north and northwest forming a lobe in the Dvina--Vaga depression. The continuation northward, northeast of Arkhangelsk, is still somewhat uncertain, but evidence suggests that the outer margin of the Scandinavian ice sheet was situated in the Mezen drainage basin. Luminescence and radiocarbon dates suggest that the maximum position was attained after some 17 ka ago, and that deglaciation started close to 15 ka ago. This age for the maximum position is younger than the maximum position in the western peripheral areas of the Scandinavian ice sheet. This may be accounted for by initial ice build-up in the west followed by a successive migration of the ice divide(s) to the east as ice growth continued. Deglaciation was either by lateral retreat or isolation of dead ice masses causing areal downwasting.

Beschreibung: The Arkhangelsk area lies in the region that was reached by the northeastern flank of the Scandinavian ice sheet during the last glaciation. Investigations of Late Pleistocene sediments show interglacial terrestrial and marine conditions with sea level up to 52 m above the present level. An unconformity in the stratigraphy suggests a hiatus representing the Early Valdaian (Weichselian) and the beginning of the Middle Valdaian. This unconformity could be related to a low base level and isostatic depression of the area north of Arkhangelsk, either caused by ice masses advancing from the Kara and Barents ice sheets and/or to Scandinavian ice over the Kola Peninsula. During Middle Valdaian, from c. 66 ka BP, until the advance of the Late Valdaian glacier, c. 17-16 ka BP, peat formation, and northward fluvial sedimentation occurred coexisting with permafrost conditions in a later phase. Before the glacier advance, the base level rose and thick vertical accumulations of fluvial sediments were formed. Associated with this glacier advance from the north-northwest, ice damming occurred. Fluvial drainage was opposite to the present drainage pattern and deposition appeared in glaciolacustrine ponds in the area outside the limit of the glaciation. After the deglaciation that started c. 15 ka BP, permafrost conditions and downwasting of buried stagnant glacier ice prevailed until at least 10.7 ka BP.

Beschreibung: The Pyoza River area in the Arkhangelsk district exposes sedimentary sequences suitable for study of the interaction between consecutive Valdaian ice sheets in Northern Russia. Lithostratigraphic investigations combined with luminescence dating have revealed new evidence on the Late Pleistocene history of the area. Overlying glacigenic deposits of the Moscowian (Saalian) glaciation marine deposits previously confined to three separate transgression phases have all been connected to the Mikulinian (Eemian) interglacial. Early Valdaian (E. Weichselian) proglacial, lacustrine and fluvial deposits indicate glaciation to the east or north and consequently glacier damming and meltwater run-off in the Pyoza area around 90-110 ka BP. Interstadial conditions with forest-steppe tundra vegetation and lacustrine and fluvial deposition prevailed at the end of the Early Valdaian around 75-95 ka BP. A terrestrial-based glaciation from easterly uplands reached the Pyoza area at the Early to Middle Valdaian transition around 65-75 ka BP and deposited glaciofluvial strata and subglacial till (Yolkino Till). During deglaciation, laterally extensive glaciolacustrine sediments were deposited in ice-dammed lakes in the early Middle Valdaian around 55-75 ka BP. The Barents–Kara Sea ice sheet deposited the Viryuga Till on the lower Pyoza from northerly directions. The ice sheet formed the Pyoza marginal moraines, which can be correlated with the Markhida moraines further east, and proglacial lacustrine deposition persisted in the area during the first part of the Middle Valdaian. Glacio-isostatic uplift caused erosion followed by pedogenesis and the formation of a deflation horizon in the Middle Valdaian. Widely dispersed periglacial river plains were formed during the Late Valdaian around 10-20 ka BP. Thus, the evidence of a terrestrial-based ice sheet from easterly uplands in the Pyoza area suggests that local piedmont glaciers situated in highlands such as the Timan Ridge or the Urals could have developed into larger, regionally confined ice sheets. Two phases of ice damming and development of proglacial lakes occurred during the Early and Middle Valdaian. The region did not experience glaciation during the Late Valdaian.