If plateau ice was cold-based, lateral and frontal moraines will be found in the valleys only, but if some plateau ice was warm-based, moraines may be found on top of, or leading onto, the plateau from the surrounding valley-head outlets. Valley moraines tend to be dominated by large, cobble- to boulder-size, angular material, indicating that the dominant debris source is rock fall. Where considerable thicknesses of valley floor sediments are available, outlet glaciers may construct large end-moraine sequences, especially where proglacial thrusting takes place. This appears to be most effective where retreat-driven isostatic rebound allows aggradation of permafrost, creating a 'potential' shallow décollement surface within the valley floor sediments.
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