Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 44-46).

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 32-33.

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Thesis (Ph.D.)--Boston University / The Antarctic Plateau is defined on the basis of elevation and slope, being above 2000 meters and with less than a one-degree slope in East Antarctica and being above 1500 meters with less than a one-degree slope in West Antarctica. This region is presented as a high latitude, high elevation, cold desert. It is shown to be a near homogenous geographical region, with a uniform snow surfaace, relatively little local relief, and great depths of snow. Its climate is controlled to a large degree by its geographical location. Elevation, slope, and distance from the coast are presented as the three most important geographical elements [TRUNCATED]

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.

The West Antarctic Ice Sheet (WAIS) is mostly grounded in broad, deep basins (down to 2.5 km below sea level) that are stretched between five crustal blocks. The geometry of the bedrock, being mostly below sea level, induces a fundamental instability in the WAIS through the possibility of runaway grounding line retreat. The crustal environment of the WAIS further influences the ice sheet’s fast flow through conditions at the ice-bedrock boundary. This study focuses on understanding the WAIS by examining the subglacial geology (such as volcanoes and sedimentary basins) at the icebedrock boundary and the continent’s deeper crustal structure- primarily using airborne gravity anomalies. The keystone of this study is a 2004-2005 aerogeophysical survey over one of the most negative mass balance glaciers on the continent: Thwaites Glacier (TG). The gravity anomalies derived from this dataset- as well as gravity-based modeling and spectral crustal boundary depth estimates- reveal a heterogeneous crustal environment beneath the glacier. The widespread Mesozoic rifting observed in the Ross Sea Embayment (RSE) of West Antarctica extends beneath TG, where the crust is ~27 km thick and cool. Adjacent to TG, spectrally-derived shallow Moho depths for the Marie Byrd Land (MBL) crustal block can be explained by thermal support from warm mantle. I assemble here new compilations of free-air and Bouguer gravity anomalies across West Antarctica (from both airborne and satellite datasets) and re-interpret the extents of West Antarctic crustal block and their boundaries with the rift system. Airy isostatic gravity anomalies reveal that TG is relatively sediment starved, in contrast to the sediment-rich RSE. TG’s fast flow velocities could be sustained in this sediment poor environment if higher heat flux in MBL was providing an ample source of subglacial melt water to the glacier. The isostatic anomalies also indicate that TG’s outlet rests on a bedrock sill that will impede future grounding line retreat (up to ~100 km) and temporarily stabilize the glacier. / text

The subjects for this study are two subglacial lakes -- Vostok and Concordia -- located in East Antarctica. Lake Vostok is the largest known subglacial lake on Earth. Melting and freezing at the ice-water contact are known to occur in both lakes. These internal processes are important subjects for numerical modeling. The precise knowledge of the lake's bathymetry and the distribution of unconsolidated sediments at the bottom of the lake are required boundary conditions for such modeling. The ultimate goal of this research was to develop 3D bathymetry models and to establish the distribution of unconsolidated sediments for both lakes. Joint interpretation of airborne gravity and seismic data was performed for Lake Vostok, revealing that the lake is hosted by consolidated sedimentary rocks. The modeling shows that Lake Vostok consists of two sub-basins: a larger, deeper one with water thickness exceeding 1000 m in the south and a shallower one with a water thickness of about 250 m in the north. The resulting 3D model has a substantially better correlation with seismic data than two previous models. Lake Concordia appears to be significantly shallower with water thicknesses not exceeding 200 m for all possible host rock densities. Since the lake is relatively shallow, the sediment layer cannot be resolved. A similar pattern of freezing and melting was observed in Lake Concordia and Lake Vostok: the deeper part of the lake lies under thinner ice and is dominated by the freezing of water at the ice bottom, while in the shallower part of the lake the overlying thicker ice melts. The analysis of seismic data in four different locations over Lake Vostok revealed the presence of unconsolidated sediments at the bottom of the lake. The sedimentary layer appears to be thicker (up to 400 m) in the northern basin, while its thickness does not exceed 300 m in the southern one. Four different sedimentation mechanisms were considered to explain how such a thick sedimentary layer was deposited in Lake Vostok under glacial conditions. The estimates show that none of the mechanisms considered is capable of depositing the observed sedimentary layer, revealing the pre-glacial origin of Lake Vostok.

Abstract not available