Associate Professor Kathy Licht, Department of Earth Sciences, IUPUI
Till in an extensive blue ice moraine in the central Transantarctic Mountains shows relatively continuous deposition by East Antarctic derived ice throughout the last glacial cycle. The well-preserved moraine consists of quasi-continuous, hummocky sediment ridges that form on top of sublimating ice. Ground-penetrating radar (GPR) imaging of the internal structure beneath the moraine’s debris cover shows that the moraine formed through the lateral accretion of basal debris-rich ice layers thrust upward over time. Pebble lithology and detrital zircon geochronology reveal distinct spatial changes between dominant sedimentary (Beacon) and igneous (Ferrar) composition at both meter and kilometer scales. The provenance changes observed in the pebble fraction are interpreted to indicate relative stability of the East Antarctic ice sheet, as the Law Glacier tapped into and eroded successively lower stratigraphic units of the Beacon Supergroup. We also analyzed stable isotope values, which indicate warm-based ice upstream of this site. Together these datasets suggest that Antarctic blue ice moraines may be repositories of sediment from the warm-based portions of ice on the polar plateau and provide valuable archives of ice sheet and geologic history around the continent.
|Date||Wednesday, 18 March 2020|
|Time||1:00pm - 2:00pm|
|Location||Benson Common Room (Room Gn9, Geology)|