HR: 1340h
AN: H53D-0500    [Abstracts]
TI: Geomorphic characterization of the Fortymile Wash alluvial fan, Nye County, Nevada, in support of the Yucca Mountain Project
AU: * Cline, M
EM: mcline@email.arizona.edu
AF: Los Alamos National Labs, Earth and Environmental Sciences Division, Los Alamos Natl. Lab P.O. Box 1663, Los Alamos, NM 87545 United States
AU: * Cline, M
EM: mcline@email.arizona.edu
AF: Department of Geosciences University of Arizona, Gould-Simpson Building #77, 1040 E 4th St, Tucson, AZ 85721 United States
AU: DeLong, S
EM: sdelong@geo.arizona.edu
AF: Los Alamos National Labs, Earth and Environmental Sciences Division, Los Alamos Natl. Lab P.O. Box 1663, Los Alamos, NM 87545 United States
AU: DeLong, S
EM: sdelong@geo.arizona.edu
AF: Department of Geosciences University of Arizona, Gould-Simpson Building #77, 1040 E 4th St, Tucson, AZ 85721 United States
AU: Pelletier, J
EM: jon@geo.arizona.edu
AF: Department of Geosciences University of Arizona, Gould-Simpson Building #77, 1040 E 4th St, Tucson, AZ 85721 United States
AB: In the event of an unlikely volcanic eruption through the proposed high-level radioactive waste repository at Yucca Mountain, contaminated ash may be deposited in portions of the Fortymile Wash drainage basin and subsequently redistributed to the Fortymile Wash alluvial fan by fluvial processes. Characterization of the Fortymile Wash alluvial fan has been undertaken as part of an effort to quantify the transport of contaminated ash throughout the fluvial system, especially to define the spatial distribution of fluvial activity over time scales of repository operation, and the rates of radionuclide migration into different soils on the fan. The Fortymile Wash alluvial fan consists of extremely low relief terraces as old as 70 ka. By conducting soils-geomorphic mapping and correlating relative surface ages with available geochronology from the Fortymile Wash fan and adjacent piedmonts, we identified 4 distinct surfaces on the fan. Surface ages are used to predict the relative stability of different areas of the fan to fluvial activity. Pleistocene-aged surfaces are assumed to be fluvially inactive over the 10 kyr time scale, for example. Our mapping and correlation provides a map of the depozone for contaminated ash that takes into account long-term channel migration for the time scales of repository operation, and it provides a geomorphic framework for predicting radionuclide dispersion rates into different soils across the fan. The standard model for vertical migration of radionuclides in soil is diffusion; therefore we used diffusion profiles derived from ¹³⁷Cs fallout to determine radionuclide infiltration rates on the various geomorphic surfaces. The results show a strong inverse correlation of the geomorphic surface age and diffusivity values inferred from the ¹³⁷Cs profiles collected on the different surfaces of the fan.
DE: 1824 Geomorphology: general (1625)
DE: 1825 Geomorphology: fluvial (1625)
DE: 1826 Geomorphology: hillslope (1625)
DE: 1847 Modeling
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: Fall Meeting 2005