BASAL ICE ACCRETION AND DEBRIS ENTRAINMENT WITHIN THE COASTAL ICE MARGIN, LAW DOME, ANTARCTICA

Basal ice stratigraphy in coastal ice cliffs at the Law Dome margin ha s revealed the basal accretion d clean and debris-bearing ice, marine congelation ice and granular marine ice inland of the margin. Co-isoto pic analysis of deltaO-18 and deltaD isotopes together with solute che mistry were applied to determine the modes of accretion and debris ent rainment. The marine congelation ice and the granular marine ice were formed from the basal freezing of desalinated sea water and the episod ic mixture of basal meltwater and sea water, respectively. Two differe nt debris-entrainment mechanisms were identified. Debris-band ice with debris concentrations of 6.3-33% (by volume) was formed from proglaci al raised beach and shallow marine sediment incorporated by an over-ri ding advance of the margin. Two other debris-bearing ice types, disper sed debris-poor ice with debris concentrations <0.3% (by volume) and l aminated debris ice with debris concentrations 0.9-1.9% (by volume) we re accreted further inland from the margin by basal regelation process es associated with the Robin (1976) heat-pump effect.