FACTORS INFLUENCING MAGNETIC SUSCEPTIBILITY IN THE PALOUSE LOESS

Magnetic susceptibility is an inexpensive technique that has been successfully used to reconstruct paleoclimate in loess-paleosol sequences. However, magnetic susceptibility is a function of the abundance, type, and size distribution of magnetic particles, which in turn can be affected by paleoenvironmental parameters such as pedogenesis and wind strength. Thus, the paleoenvironmental interpretation of magnetic susceptibility is site-specific. Our study focused on a well-studied loess-paleosol sequence in the Palouse loess near Clyde, southeastern Washington, USA. We measured magnetic susceptibility (low-frequency and frequency dependent), particle size, Fe abundance, induced isothermal remanent magnetization, and temperature-dependent magnetic susceptibility of loess along a depth profile to study what controls magnetic susceptibility in the Palouse loess. Magnetic susceptibility at the Clyde site varies systematically with depth. Magnetic properties such as the Curie temperature are consistent with magnetite and/or maghemite as the dominant carriers, with very little hematite. Magnetic susceptibility of loess at Clyde is not well correlated with individual variables like Fe content; instead, multiple factors may interact to yield the magnetic susceptibility signal.