Along with our colleagues Kate Swanger, Doug Kowalewski, and Joerg Schaefer, we are examining the role of physical and chemical weathering in modifying the inventory of cosmogenic nuclides in exposed rocks. In our collaborative NSF grant, entitled Multi-nuclide approach to systematically evaluate the scatter in surface exposure ages in Antarctica and to develop consistent alpine glacier chronologies, we seek to investigate the impact of Earth-surface processes on the application of cosmogenic exposure dating in Antarctica by combining multi-nuclide techniques, detailed field experiments, rock-mechanic studies, and climate modeling.
We will analyze cosmogenic-nuclide inventories for a suite of six alpine-moraine systems in inland regions of the McMurdo Dry Valleys. This area is ideally suited for this study because 1) the targeted alpine moraine sequences are critically important in helping to reconstruct past temperature and precipitation values over the last several million years, 2) the production rates for cosmogenic nuclides are typically high and well-known, and 3) the complexity of surface processes is relatively low. Our work has two specific goals: to evaluate the effects of episodic geomorphic events in modulating cosmogenic inventories in surface rocks in polar deserts and to generate an alpine glacier chronology that will serve as a robust record of regional climate variation over the last several million years. A key objective is to produce a unique sampling strategy that yields consistent exposure-age results by minimizing the effects of episodic geomorphic events that obfuscate cosmogenic-nuclide chronologies. We will link our moraine chronology with regional-scale atmospheric models developed by collaborators at University of Massachusetts Amherst.
NSF Award Abstract
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(* Student Advisee)
*Swanger, K.E., Marchant, D.E., Schaefer, J.M., Winckler, G., and Head, J.W., 2011. Elevated East Antarctic outlet glaciers during warmer-than-present climates in southern Victoria Land. Global and Planetary Change, Volume 79, Issues 1-2, 61-72. doi:10.1016/j.gloplacha.2011.07.012
*Swanger, K.M., Marchant, D.R., Kowalewski, D.E., and Head, J.W. 2010. Viscous flow lobes in central Taylor Valley, Antarctica: Origin as remnant buried glacial ice. Geomorphology 120, 174-185. doi:10.1016/j.geomorph.2010.03.024
Marchant, D.R., *Lewis, A., Phillips, W.C., *Moore, E.J., Souchez, R., and Landis, G. P. 2002. Formation of patterned-ground and sublimation till over Miocene glacier ice in Beacon Valley, Antarctica. Geological Society of America Bulletin 114, 718-730.
Summerfield, M.A., Sugden, D.E., Denton, G.H., Marchant, D.R., Cockburn, H.A.P., and Stuart, F.M., 1999. Cosmogenic isotope data support previous evidence of extremely low rates of denudation in the Dry Valleys region, southern Victoria Land, Antarctica. Geological Society of London, Special Publication 162, 255-267.
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