MAGNETIC SUSCEPTIBILITY OF THE PALOUSE LOESS AS A PALEOCLIMATE INDICATOR

The Palouse loess covers much of eastern Washington and parts of Idaho and Oregon. The Palouse loess is reworked eolian silt originally deposited by glacial outburst floods during the late Pleistocene. These deposits can range from less than one meter to over 75m thick. The magnetic susceptibility of sediment in loess deposits has been used to reconstruct hundreds of thousands of years of past climate in Alaska, Siberia, and central China. However, this technique has not been used in the Palouse loess. We measured the magnetic susceptibility of loess from a previously studied outcrop northwest of Walla Walla, WA and compared it to published paleoclimate data. Magnetic susceptibility of the sediments changes consistently and measurably with time. We measured grain size to test the hypothesis that changes in grain size influence the magnetic susceptibility. If these variables are correlated, grain size may be a useful proxy for paleoclimate in the Palouse.