Ice-Rafted Debris (IRD)
Introduction
Ice-rafted debris (IRD) is sediment of any grain size that has been transported by floating ice and released subsequently into an aqueous environment; the ice acts as a raft, providing buoyancy to any debris included within it or on its surface. Although IRD is often assumed to be transported by icebergs, the ice raft can be in the form of either icebergs, derived from glaciers and ice sheets, or from sea ice formed by the freezing of sea water. IRD is usually deposited by icebergs and sea ice floating in marine waters, but icebergs, lake and river ice can also transport debris and release it subsequently into lakes.
Sources and distribution of debris
The best-known source of IRD is from glaciers and ice sheets. This form of IRD is heterogeneous in grain size, ranging from fine clays and silts to large boulders. This is because glacier ice can erode and transport material of all grain sizes. Sediments produced in the zone of shearing and crushing at the base of an ice...
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