THE GEOCHEMICAL PARADOX OF ICE-COMPLEX SEDIMENTS IN NORTH SIBERIA

Icy silty deposits in northern Siberia, here termed 'ice-complex sedim ents' (ICS), have a higher salinization than other continental deposit s of Neogene-Pleistocene age. Data for salinity (%) and the ratio of C a ion content to Cl ion content for samples from the Yana-Indigirskaya and Kolymskaya lowlands Indicate that the salinization of Pleistocene permafrost is lowest, that icy silts have salinities between 0.1% and 1.0%, and that recent floodplain, coastal and alas deposits have sali nities greater than 1%. These differences are thought to reflect the p hase change in gas-liquid inclusions in crystals and rocks when they b reak and their contents (solutions) are released during freezing. This process is termed cryocryptogenesis. It is concluded that ICS deposit s were formed under less humid and colder conditions than exist today in northern Yakutia, but more humid than central Yakutia.