During the Early and Middle Pleistocene and the early part of the Late Pleistocene persistent downwarping led to a major transgression in northern West Siberia, extending generally from the Polar Urals to the Central Siberian Plateau. This transgressive phase began in the Tobol'sk period of the Early Pleistocene and reached its maximum during Salekhard time; the Kazantsev period was largely a regressive phase. Minor regressions at the end of the Tobol'sk and Salekhard periods saw the accumulation of unstratified “drift‐like”; deposits in which transport by icebergs and sea ice played a major role. No continental ice sheets existed in this area during the traditional glacial epochs of the Early and Middle Pleistocene.