The expansion of the zone of ice rafting around Antarctica is believed by some glacial geologists to coincide with the expansion of glaciers. The initial appearance of ice-rafted debris in the geologic record of the Southern Ocean Waters is believed to mark the initiation of the Antarctic Ice Sheet. Subsequent increases and decreases in the quantity of ice rafted debris are interpreted to indicate expansions and contractions of the Antarctic Ice Sheet. It should be noted, however, that there is considerable debate over the interpretation of ice rafted material, its initial appearance in sedimentary cores, and its significance. There is an overall increase in the amount of sand and gravel in deep sea sediment cores in sediments younger than about 34 million years.
Many glacial environments produce sediment.
Because the physical and chemical setting varies in each of the different glacial environments, a different sediment is produced. For example, under the ice sheet abrasion and plucking produce till. Till has very specific characteristics. Till is a poorly sorted, well mixed sediment with angular clasts. It does not contain any modern microfossils.