HR: 1340h
AN: PP33C-1607    [Abstracts]
TI: Variations In The Microstructure Of Polycrystalline Ice From Vostok, Antarctica
AU: * Obbard, R W
EM: rachel.w.obbard@dartmouth.edu
AF: Dartmouth College, Thayer School of Engineering 8000 Cummings Hall, Hanover, NH 03755 United States
AU: Baker, I
EM: ian.baker@dartmouth.edu
AF: Dartmouth College, Thayer School of Engineering 8000 Cummings Hall, Hanover, NH 03755 United States
AB: The 3623 m 5G-1 core collected at Vostok Station, Antarctica contains alternating zones of distinctly different microstructure, the study of which may tell us something about the climate and glacial history of this part of the Antarctic and improve our interpretation of other ice core records. Sixteen specimens of Vostok meteoric ice, from depths of 249 m to 3416 m, have been analyzed using a variety of characterization techniques including optical image analysis, scanning electron microscopy, and electron dispersive spectroscopy. We have also recently begun using a new technique, electron backscatter diffraction to analyze the orientation of both c and a-axes and the distribution of grain boundary misorientations. Our analysis confirms the presence of two distinct types of microstructure in the Vostok core and yields new information on their differences. The ice associated with interglacial periods is characterized by a relatively coarse-grained texture and a strong preferred orientation of the c-axes in a plane across the vertical, producing a vertical girdle fabric. In contrast, glacial period ice is characterized by a much smaller grain size and a strong single maximum fabric, with c-axes clustered around the vertical. We present these differences, and discuss their correlation with the geochemical and climate data, in an effort to explain the deposition, deformation and recrystallization processes that created them.
DE: 0720 Glaciers
DE: 0724 Ice cores (4932)
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 9310 Antarctica (4207)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005