The Margin of the Last Barents-Kara Ice Sheet at Markhida, Northern Russia

Abstract

The Markhida Moraine is a broad zone of ice marginal landforms and deposits running E-W across the Pechora lowland in northern Russia. It was formed along the southern margin of an ice sheet advancing onto the coast from the Kara Sea. Previous researchers (Grosswald, 1980, 1983, 1994a: Grosswald et al., 1974) concluded that the moraine was formed during a readvance of the Barents-Kara ice sheet after 9000 14C yr B.P. This conclusion was based on the occurrence of deformed lacustrine sediments dated 9000 to 10,000 14C yr B.P. between two presumed basal tills in the type section at Markhida. A reinvestigation of the section by the authors revealed only one basal till overlain by lacustrine sediments and diamictons, yielding radiocarbon dates between 9000 and 10,000 14C yr B.P. Luminescence dating from the sand underlying the till gave Middle Weichselian ages. Deformation structures and fabric in the sediments overlying the till solely reflect gravity-driven processes, not glaciotectonic deformation as claimed by previous investigators. We conclude that most of these sediments were finally deposited during very slow (retarded) melting of a large body of buried glacier ice and the underlying permafrost. Thus, the Markhida Moraine, as an ice marginal feature, was formed prior to 10,000 14C yr B.P., probably during the Late Weichselian, but possibly as early as the Middle Weichselian.