Fluvioglacial Drift

the deposits of glacial meltwater streams. Two types of fluvioglacial drift are distinguished: proglacial deposits and ice-contact deposits.

Proglacial deposits are formed ahead of the snout of a glacier by meltwater flowing from under the margin of the glacier. Such deposits constitute outwash plains and fluvioglacial terraces, as well as certain ice-margin and radial eskers. The eskers, which are produced by the merging of deltas that accumulate at the sites where meltwater emerges from under the margin of a glacier, are found in the region where the glacier descends into a lake or sea. The contents of proglacial deposits rapidly change from coarse pebbles and cobbly sand to fine-grained cross-bedded sand with increasing distance from the margin of the glacier.

Ice-contact deposits are formed by meltwater flowing through tunnel valleys, ice-walled trenches, and moulins. Such deposits constitute unique landforms called eskers and kames. Ice-contact deposits are greatly heterogeneous in structure. The heterogeneity arises as a result of variations in the contents of the deposits in the area where the drift accumulates. The deposits may contain pebbles, gravel, and poorly sorted or well-scoured cross-bedded sand of various grain sizes ranging down to fine-grained.