Article
Article
Till
Article By:
Johnson, W. Hilton Department of Geology, University of Illinois at Urbana-Champaign, Champaign, Illinois.
Last reviewed:December 2019
DOI:https://doi.org/10.1036/1097-8542.697200
Sediment deposited directly from glacier ice. Till is characteristically nonsorted and nonstratified and is deposited by lodgment or melt-out beneath a glacier or by melt-out on the surface of a glacier. The texture of till varies greatly (see illustration) and while all tills are characterized by a wide range of particle sizes, some are predominantly fine-grained (clayey or silty), while others are medium-grained (silty or sandy) or coarse-grained (gravelly or stony). Till contains a variety of rock and mineral fragments which reflect the source material over which the glacier flowed. The particles in the deposit usually show a preferred orientation related to the nature and direction of the ice flow. The overall character of the till reflects the source material, position and distance of transport, nature and position of deposition and postdepositional changes.
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