ABSTRACT
Tills of the central part of the Don ice sheet are described from the Khopior River Basin near the towns of Novokho-piorsk, Uvarovo, Muchkap and others. The Oka Till has been studied in its stratotype region in the Oka River area. The basal till consists of two to three layers: a red-yellow-brown and a dark brown diamicton with no clear boundary between them, and in many cases, a third layer of dark grey diamicton occurs beneath the previous unit. These basal tills are characterised by high density that increases down the profile, especially in the lower dark-brown unit. Distribution of erratic material in the tills occurs in a particular regularity. It can be shown that the debris composition of the Don Tills in the northern provinces largely comprises material from Scandinavian source areas. The greenish-brown Oka Till, found in the Moscow area beneath two Middle Pleistocene tills, is characterised by both a high clay and a high gravel content.
