Frozen, ice-rich paleosol sequences with large ice wedges are widely distributed along the coast of shelf seas and the large rivers in central and eastern Siberia. These sequences are 14C dated between >50 and 12 ka BP. The spatial distribution of Ice Complex deposits is connected with vast, numerous thermokarst lakes formed during the Holocene warming, leading to substantial thawing of ice-rich permafrost deposits.The origin and formation of these 10 to 50 m thick sediments is uncertain and discussed for more than hundred years. At the end of the 19th Century, Eduard von Toll gave the first interpretation, describing ?stone ice? as glacier remains, where glacier fissures were filled with moraine material. Later, in the 20th Century, the deposits have been controversially interpreted as being of glaciolacustrine, fluviolacustrine,alluvial, eolian or multigenetic origin.Since 1998, Ice Complex sequences around the Laptev Sea have been studied within the multidisciplinary framework of joint Russian-German expeditions. The sequences are characterized by comparable cryolithogenetical,sedimentological, hydrochemical as well as paleo-ecological signatures, and include always the same Late Pleistocene stratigraphical units (Zyryanian Stadial, Karginian Interstadial, Sartanian Stadial).The deposits occur as a widely distributed cover on plains with low inclination in front coastal range orsurrounding rocky hills.The formation of the Ice Complex cover is assumed to be connected with an increased occurrence of perennialsnowfields and niveo-eolian accumulations during the Late Pleistocene. Abundant niveo-aeolian solid matter was probably collected therein. Because of an extreme continentality with low precipitation, only snowfields survived, unlike the formation of glacier ice sheet in western Eurasia during this cold period.Numerous snowfields at the slopes of arctic mountains as well as in the wide spread plains in front were sources of both water for braided streams crossing the accumulation plain and for clastic material formingIce Complex deposits. The typical bi- and multimodal grain-size distribution of these sediments indicatethat various kinds of transportation and accumulation took place more or less relating to snowfield processes.The paleogeographical situation has to be considered in connection with the dry Arctic shelf areasexisting contemporaneously. Only a little drainage took place on these large flat areas and therefore waterfrom snowfields flowed broadly without clear fluvial orientation over the shelf, where large ice-wedge polygonsystems were formed. Their growth was supported by meltwater coming from snow patches as well as suspended clastic matter transported by numerous streams. Plant and fauna remains indicate the existence of a spotty mosaic of dry and wet patches. The terms ?tundra-steppe? and ?mammoth fauna? characterizethis paleoenvironment. In this landscape the mammoth fauna existed until 12 ka BP, that is, until the end of Ice Complex formation.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL6-Earth climate variability since the Pliocene