ABSTRACT
The lithological characteristics of the Valdai Glacial deposits of the northwestern parts of the Russian Plain display characteristic patterns of occurrence and specific facies. In thin sections, the sand grains and even the smaller particles are clearly orientated in the direction of radially spreading ice tongues. The unusually clay-rich composition of the glacial deposits is explained by large-scale entrainment of glaciolacustrine clays that filled vast depressions over which the Valdai ice advanced. The Middle Pleistocene till differs from the Valdai Till by its much coarser grain-size composition; the former is mostly represented by a coarse sandy diamicton with abundant gravel. The major characteristic of the Middle Pleistocene till is its markedly lower hornblende content. The glacial debris has wide granulometric and petrographic spectra, runoff in the proglacial zone sorts the material, whilst simultaneously marginal ridges are formed at the ice front.
