Antarctic ice-rafted detritus (IRD) in the South Atlantic: Indicators of iceshelf dynamics or ocean surface conditions?

Ocean sediment core TN057-13PC4/ODP1094, from the Atlantic sector of the Southern Ocean, contains
elevated lithogenic material in sections representing the last glacial period compared to the Holocene. This ice-rafted
detritus is mainly comprised of volcanic glass and ash, but has a significant input of what was previously interpreted as
quartz during peak intervals (Kanfoush et al., 2000, 2002). Our analysis of these clear mineral grains indicates that most
are plagioclase, and that South Sandwich Islands is the predominant source, similar to that inferred for the volcanic
glass (Nielsen et al., in review). In addition, quartz and feldspar with possible Antarctic origin occur in conjunction with
postulated episodes of Antarctic deglaciation. We conclude that while sea ice was the dominant ice rafting agent in the
Polar Frontal Zone of the South Atlantic during the last glacial period, the Holocene IRD variability may reflect
Antarctic ice sheet dynamics.