Late Weichselian Ice Sheet of Northern Eurasia

Abstract

A considerable portion of Northern Eurasia, and particularly its continental shelf, was glaciated by inland ice during late Weichsel time. This was first inferred from such evidence as glacial striae, submarine troughs, sea-bed diamictons, boulder trains on adjacent land, and patterns of glacioisostatic crustal movements. Subsequently, the inference was confirmed by data on the occurrence and geographic position of late Weichselian end moraines and proglacial lacustrine deposits.The south-facing outer moraines in the northeastern Russian Plain, northern West Siberia, and on Taimyr Peninsula are underlain by sediments containing wood and peat, the radiocarbon dating of which yielded ages of 22,000 to 45,000 yr B.P. The youngest late-glacial moraines are of Holocene age: the double Markhida moraine in the lower Pechora River basin, presumably associated with “degradational” surges of the Barents Ice Dome, is underlain by sediments with wood and peat dated at 9000 to 9900 yr B.P.: this suggests that deglaciation of the Arctic continental shelf of Eurasia was not completed until after 9000 yr B.P.The reconstructed ice-front lines lead to the conclusion that the late Weichselian ice sheet of Northern Eurasia (proposed name: theEurasian Ice Sheet) extended without interruptions from southwestern Ireland to the northeastern end of Taimyr Peninsula, a distance of 6000 km: it covered an area of 8,370,000 km2, half of which lay on the present-day continental shelves and a quarter on lowlands that were depressed isostatically below sea level. Hence, the ice sheet was predominantly marine-based.A contour map of the ice sheet based both on the dependence of the heights of ice domes upon their radii and on factual data concerning the impact of bedrock topography upon ice relief has been constructed. The major features of the ice sheet were the British, Scandinavian, Barents, and Kara Ice Domes that had altitudes of 1.9 to 3.3 km and were separated from one another by ice saddles about 1.5 km high. At the late Weichselian glacial maximum, all the main ice-dispersion centers were on continental shelves and coastal lowlands, whereas mountain centers, such as the Polar Urals and Byrranga Range, played only a local role.The portions of the ice sheet that were grounded on continental shelves some 700 to 900 m below sea level were inherently unstable and could exist only in conjunction with confined and pinned floating ice shelves that covered the Arctic Ocean and the Greenland and Norwegian Seas.The Eurasian Ice Sheet impounded the Severnaya Dvina, Mezen, Pechora, Ob, Irtysh, and Yneisei Rivers, and caused the formation of ice-dammed lakes on the northern Russian Plain and in West Siberia. Until about 13,500 yr B.P. the proglacial system of lakes and spillways had a radial pattern; it included large West Siberian lakes, the Caspian and Black Seas, and ended in the Mediterranian Sea. Later, the system became marginal and discharged proglacial water mainly into the Norwegian Sea.

Geometry and rate of faulting in the North Baikal Rift, Siberia

“…By contrast, the clearest and largest offsets of the S1 generation are observed along the northern Lake Baikal, and the Barguzin, Kitchera, and Upper Angara basins (Figures 1 and 2). deposits from the deglaciations between cold periods of 40-35 ka and 26-13 ka, while the 17+_2 ka old deposits in the Vitim area, rarely sampled and poorly preserved, could be linked to proglacial lakes [Grosswald, 1980]. Well-preserved terraces 15-18 m high thus date the early postglacial warming at -10 ka.…”

Differences between the last two glacial maxima and implications for ice-sheet, δ18O, and sea-level reconstructions

“…(Largely) floating Arctic ice shelves during glacial intervals were proposed in the 1970s and 1980s (Mercer, 1970;Hughes et al, 1977;Broecker, 1975;Grosswald, 1980;Denton and Hughes, 1981;Williams et al, 1981;Chappell and Shackleton, 1986), but then were overlooked due to difficulties in obtaining data from the region and a lack of direct evidence for such shelves during the LGM (for an overview, see Jakobsson et al, 2016). Recent geophysical mapping in the Arctic, however, has led to a re-evaluation of large floating Arctic ice shelves during the Pleistocene.…”

New organic-walled dinoflagellate cysts from recent sediments of Central Asian seas

“…In the Middle Pliocene, orogenic activity separated the southern part of the Caspian Sea from the Black Sea but later they were temporarily reconnected, where the Caspian Sea was part of a slightly salty Pontic lake. The Caspian Sea was connected to the Aral Sea during the Pliocene and Pleistocene as the result of major transgressions linked to large-scale influx of melt water from high latitude ice caps (Dumont, 1998;Grosswald, 1980Grosswald, , 1993Mamedov, 1997). For the last 300 ka, the Caspian Sea has existed as an isolated water body (Boomer et al, 2000), awith some short transgressive episods associated with interglacial periods and global sea-level changes (Svitoch et al, 2000).…”