Abstract

Dropstone, dump, and grounding structures, resulting from the melt-out of debris contained in floating and grounded icebergs, are described from a Pleistocene ice-marginal, glacio-lacustrine sequence in Scotland. Dropstones display bending penetration, rucking, and complete rupture of stratum occurring beneath them, and onlap above them, with the degree of deformation varying as a function of the size, shape, and axial disposition of the clast and of the sediment type into which they fell. Dump structures are conical mounds of gravel or diamict formed by the break-up and overturning of dirt-laden icebergs and the consequent release of large quantities of debris to the lake floor. Grounding structures are caused by the grounding of icebergs, the down-warping of underlying lake-floor sediment, and the subsequent in situ melt-out of contained debris to form isolated troughs of diamict.

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