Till deposits are unsorted mixtures of rocks, clay and sand sized particles deposited by ice. In the UK it is often known as boulder clay because of the large boulders carried supraglacially, will be dropped amongst subglacial rock flour when the glacier retreats. Individual load items are likely to be sub-angular i.e. not rounded like fluvioglacial deposits, but not sharply angled as freshly weathered deposits. Which will be one field observation when distinguishing differences.
Examples of glacially deposited landforms that you would distinguish from fluvioglacial ones are; rogen moraine, which are lateral bands of glacial till formed beneath the glacier. These are probably formed in areas of extension flow where transverse crevasses at the base of the glacier allow build up of englacial and subglacial debris. When the glacier advances rogen moraines may be broken up into drumlins. Drumlins are rounded mounds/hills of glacial till. Shaped like half an egg, with the blunt end upslope, known as the stoss end. The flatter streamline end is the lee end. They may be the result of localised surplus of glacial load that cannot be transported by the glacier. Or it may be the result of deformation of subglacial ice producing areas of lower pressure that allows till accumulation. Drumlins are often found at confluence of tributary glaciers and where glaciers spread out into plains. Crag and tail are where resistant outcrops of rocks project into the base of the glacier, deposition may occur in the zone of lower pressure downstream of obstruction. This is streamlined by glacier movement to produce a tail for the crag. So these are the features and landforms that will distinguish them from fluvioglacial landforms. These landforms will be much rougher, not very rounded, and will not be sorted into different layers, unlike fluvioglacial landforms.
Fluvioglacial deposits are sorted vertically and horizontally and consist of particles that are more rounded than glacial deposits. Material is deposited by meltwater because of a loss of energy, for example when water enters a lake or when there is a sudden drop in discharge. The most important features formed by fluvioglacial erosion are meltwater channels. Such channels may be proglacial, marginal, subglacial or overflow channels.
An example of an area that under-went fluvioglacial erosion is Britain. As the ice sheet moved southwards over Britain during the Ice Age, rivers flowing northwards were blocked. Proglacial lakes built up between the ice sheet front and higher ground. Eventually a lakes level would rise high enough to overflow at the lowest point of its rim. As the water flowed out rapid erosion would cut an overflow channel e.g. North Yorkshire. Water was dammed by the ice sheet to form a series of lakes in the Eskdale Valley, lined to each other by marginal channels. As the water overflowed to the south the large overflow channel of Newtondale was cut, leading to a further proglacial lake: Lake Pickering. This in turn overflowed through another overflow channel: Kirkham Abbey Gorge. Besides the meltwater channels, this sequence of events has had other impacts: delta deposits at Pickering, lacustrine deposits marking the extent of Lake Pickering and, most significantly, a glacial diversion of drainage. Other landforms that would become distinctive from their roundness/smoothness, and layered material are such things like eskers, that are ridges of sands and gravel’s formed in a sub-glacial tunnel. Kame’s, that are irregular mounds of sands and gravel’s deposited by meltwater on or at edge of ice sheet. Kame terrace’s that are deposited by meltwater between unglaciated higher ground and edge of ice sheet. Kame delta’s, delta built into a proglacial lake. Varves are alternate layers of silt and sand deposited in fluvioglacial lakes, the coarser, lighter coloured sand is deposited in spring when meltwater stream discharge is high and load is carried at its maximum. The darker silk sized sediments are deposited in the autumn, and discharge levels are lower, and only small particles can be transported. Kettles are blocks of ice that become detached from a retreating glacier, and will be partially buried by fluvioglacial deposits. When the ice melts, its form of depression will fill with meltwater. Braided streams are fluvioglacial streams that exhibit a high degree of braiding, as seasonal fluctuations in discharge produce periods of depression.
To answer the question, the field evidence that would be examined would firstly be the shape of the landform and whether it was rounded or not. Secondly whether the material was sorted or not would give a clear indication as to whether it was glacially deposited or fluvioglacialy deposited. Also, it would seem appropriate to suggest that landforms that are located near lakes or other water features would be formed by fluvioglacial depositions.
