HR: 09:50h
AN: GP41B-06    [Abstracts]
TI: Chemical, morphological, and magnetic properties of loessic soils and the development of a multiproxy model to reconstruct paleorainfall
AU: * Zanner, C W
EM: bzanner2@unl.edu
AF: School of Natural Resources, University of Nebraska 133 Keim Hall, Lincoln, NE 68583-0915 United States
AU: Geiss, C E
EM: christoph.geiss@trincoll.edu
AF: Trinity College, 300 Summit Street, Hartford, CT 06106 United States
AB: In recent publications, we have been able to show that changes in the relative abundance of ferrimagnets along a rainfall gradient from less than 500 mm/year in southwestern Nebraska to almost 1000 mm/year in western Illinois correlates well with the modern precipitation gradient. This suggests that we can use a grain-size dependent magnetic parameter as a potential paleorainfall proxy when analyzing paleosols in central North America. Because prior attempts of others to develop a paleoclimate proxy based on magnetics alone have proved challenging, we are proposing that a multiproxy approach using other soil properties in addition to ferrimagnets will be more fruitful. Soil carbon, nitrogen, color, and depths to the top of the B horizon are examples of soil properties that have been shown to correlate to climate. We have sampled loessic soils with a truck-mounted soil probe from more than 70 stable undisturbed upland positions from Nebraska to Illinois. We described and subsampled the cores in the field. Laboratory measurements of soil carbon and nitrogen show a strong correlation to the rainfall gradient. Soil color and other morphological properties also show promise as climatic indicators. When combined with our measured magnetic parameters, such as magnetic susceptibility, anhysteretic remanent magnetization, hysteresis loops, and viscous remanent magnetization, these soil parameters will result in a robust model that tracks modern precipitation and in a promising tool that can be applied to paleosols for reconstructing paleoprecipitation.
DE: 1500 GEOMAGNETISM AND PALEOMAGNETISM
DE: 1512 Environmental magnetism
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 9360 South America
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2005 Joint Assembly