Fluvioglacial erosion and sedimentation
115
their courses. The overflowing channels that drain the lakes occur in relation to
glaciolacustrine beach or delta deposits.
3. Forms resulting from fluvioglacial sedimentation
It is well known that one of the characteristics of the fluvioglacial environment is the large
discharge fluctuations and, consequently, the transport capacity. These fluctuations result
in sudden changes in the particle sizes and rapid variations of sedimentary structures,
both laterally and vertically. In addition, they explain why many of the fluvioglacial forms
have a discontinuous character. This is emphasized by the continuous erosion that affects
these forms in areas of retreating glaciers (Menzies, 1995b). On the other hand, the
fluvioglacial materials can be mixed with deposits of glacial till in some places, and the
fluvioglacial sediments commonly are generated from reworking of glacial till (Flint,
1971). Therefore, this is an environment subject to continuous and deep changes, where
the morphology is modified by erosion and sedimentation processes.
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Figure 5.13. Eskers and ice-marginal features in the central part of the Scandinavian Ice Sheet. Eskers
form well-organized patterns and are less common in areas of sedimentary rock, where subglacial water
drains through permeable beds, (Punkari, 1997).