A COMPARATIVE STUDY OF REEDY GLACIER AND WEST ANTARCTIC ICE STREAMS, TO DETERMINE PROVENANCE OF CENTRAL ROSS SEA LAST GLACIAL MAXIMUM TILL

In January 2007, 26 samples of till from 6 different moraines along the Reedy Glacier, East Antarctica were collected with the goal of differentiating between these samples and till collected from the base of the Whillians, Kamb, and Bindschadler Ice Streams of West Antarctica. The ability to differentiate between East and West Antarctic ice will allow us to constrain ice flow into the Central Ross Sea during the Last Glacial Maximum (LGM), which has implications for more accurate reconstructions of the Ross Ice Sheet and its behavior.

Moraines sampled from the head of Reedy Glacier give insight to the geology beneath the EAIS, and may be representative of what the glacier is eroding from its bed. Samples along the trunk of the glacier capture representative rock types eroded along the length of Reedy Glacier. At each moraine 3 replicate sub-sites were selected for collection to represent the diversity of material within each moraine. Comparisons will be based on the composition of pebbles, particle size distributions, and sand petrography. Analysis of the pebble fraction shows that each sub-site contains similar rock types, however, the concentration of each rock type varies as much as 25-35%. Similar variation is also seen within the sub-site sand fraction. Both the pebble and sand fraction reflect the mapped bedrock geology. The dominant pebble types are coarse-grained felsic and intermediate igneous rocks, as well as quartzite. Similarly felsic igneous grains, quartzite, quartz, and feldspar characterize the sand fraction. Particle size analysis shows that Reedy Glacier till averages 85% sand. The subglacial West Antarctic samples contain approximately 30% sand, and equal amounts of silt and clay, approximately 35% each.

A preliminary observation of the sand fraction from beneath the West Antarctic Ice Streams shows composition substantially different from Reedy Glacier. Sand sized polymict grains dominate material from the base of Whillans and Bindschadler Ice Streams, whereas material from the base of Kamb Ice Stream contains grains of felsic igneous, quartz, feldspar, and few to no polymict grains. In addition to the polymict grains, the sand fraction in the ice stream cores contains fragments of sedimentary, and volcanic rocks, both of which are absent from the Reedy Glacier sand fraction.