Indiana University-Purdue University Indianapolis (IUPUI) / 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 Whillans, 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 are
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
v
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.
An observation of the sand fraction from beneath the West Antarctic Ice Streams
shows composition similar to tills from Reedy Glacier. However, tills from the base of
the West Antarctic Ice Streams contain up to 75% polymict grains, and in contrast, these
grains are absent in the tills from Reedy Glacier. These 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 trace fragments of sedimentary, and volcanic
rocks, both of which are absent from the Reedy Glacier sand fraction. However, polymict
grains are believed to represent a process occurring beneath the ice sheet, rather than
indicate provenance. It is difficult to differentiate between the two tills, as both contain
high concentrations of felsic-intermediate igneous lithics, quartz, and feldspar. The
central Ross Sea contains sediment similar in rock type and mineralogy as seen within
sediments from both Reedy Glacier, and the base of the ice streams of West Antarctica.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/1695 |
| Date | 10 October 2008 |
| Creators | Kramer, Katie L. |
| Contributors | Licht, Kathy J., Swope, R. Jeffery, Barth, Andrew, 1958- |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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