DEVELOPING IRON OXIDE PROVENANCE TRACERS FOR ICE STREAMS IN THE WEDDELL SEA SECTOR OF ANTARCTICA

This study builds a library of iron oxide provenance tracers for the Weddell Sea region of Antarctica. Antarctic Ice Sheet dynamics in the Weddell Sea Sector are particularly important due to its potential effects on seal level rise, as 22% of all Antarctic ice drains through the Weddell Sea. Identification of ice rafted debris recovered in sediment cores helps determine which ice sheet sectors are prone to instability. Preservation of iron oxides due to their high hardness and lack of cleavage, combined with compositional variance and diversity of textures make iron oxides natural provenance tracers. Till samples collected from lateral moraines of the Academy, Recovery, and Foundation Ice Streams define fingerprints for the central and eastern Weddell Sea. These are augmented with bedrock samples that were pre-screened for oxide content using magnetic susceptibility from the Shackleton Range and Pensacola Mountains. Bedrock samples from the Ellsworth Mountains represent the western Weddell Sea. Till samples from the Academy and Foundation Ice Streams displayed alteration textures with V-Al bearing magnetites and titanomagnetites, as well as Al-Si-Mn bearing altered ilmenites. Samples from the Recovery Ice Stream contain Mn bearing minerals, which thus far is unique to this ice steam. Preliminary bedrock data from the Pensacola Range displayed pleonaste exsolved in magnetite, while dolerite from the Whichaway Nunataks displayed magnetite, ferrian ilmentite and Fe-Cu-Zn sulfides. These same minerals and compositions are observed in till collected from the Whichaway Nunataks. The magnetite-pleonaste texture in the Pensacola Range and Fe-Cu-Zn sulfides in the Whichaway Nunataks may potentially serve as provenance tracers, as these minerals and textures are distinctive and observed in one location each thus far. Results from this study will be used to identify sources of ice rafted debris that will be recovered in International Ocean Discovery Program (IODP) Expedition 382 to the Scotia Sea.