06/16/2022
By Erica Gavin

The Kennedy College of Science Department of Environmental, Earth and Atmospheric Sciences invites you to attend a master's thesis defense by Kimberly Lambert on "Constraining Bedrock Source Regions of Surficial Deposits in the McMurdo Dry Valleys Antarctica."


Candidate Name: Kimberly Lambert
Defense Date: Thursday, June, 30, 2022
Time: 1 to 2 p.m.
Location: Room 212, Olney, North Campus or via Zoom

Advisor: Kate M. Swanger, Department of Environmental Earth and Atmospheric Sciences

Committee Members:

  • Richard Gaschnig, Department of Environmental Earth and Atmospheric Sciences
  • Michael Krol, Bridgewater State University

Brief Abstract:

The McMurdo Dry Valleys of Antarctica contain a record of glacial fluctuations, lake level changes, and meltwater activity during the Quaternary. Samples were taken from surficial deposits in low-elevation study sites in Pearse Valley, the Rhone Glacier region in Taylor Valley, and the North Fork and South Fork regions of Wright Valley. The possible bedrock sources for unconsolidated deposits include the Skelton Group, Granite Harbor Intrusions, Beacon Supergroup, Ferrar Dolerites and McMurdo Volcanics. Samples were analyzed using X-Ray Diffraction, X-Ray Fluorescence, grain mount thin sections, and grain size analyses to constrain sample depositional environment, source regions, in situ weathering, and the possible variations in these parameters with depositional age and sampling sites. Results show that Pearse Valley, North Fork and South Fork contain material from all bedrock sources except McMurdo Volcanics. South Fork had the highest average SiO2 concentrations suggesting contributions from the Beacon Supergroup and Granite Harbor Intrusions. Rhone Glacier region contained material from Skelton Group, Beacon Supergroup and Ferrar Dolerites. Rhone Glacier samples exhibited the lowest average SiO2 and highest average MgO weight percentages of all sampling regions, likely indicative of greater contribution from the Ferrar Dolerites. Regardless of whether samples sourced from local glaciers or the East Antarctic Ice Sheet, significant differences in mineralogy or geochemistry of the glacial tills and glaciofluvial deposits were not observed. The two silt-rich samples of lacustrine or glaciolacustrine origin from Pearse Valley and North Fork had low SiO2 (50.4% and 52.0%) and high Al2O3 (11.2% and 15.1%) compared to other samples, which ranged from 54.0% to 76.0% and 5.2% to 13.4%, respectively. All samples exhibited little evidence of chemical weathering. The average Chemical Index of Alteration value was 50.4% and the average Chemical Index of Weathering Value was 54.8%. For the dated samples, the older deposits did not consistently exhibit higher weathering values. The samples with higher values were often located near a moisture source. The data support slow chemical weathering rates in hyperarid cold desert environments.