2003 Volume 109 Issue 12 Pages 697-709
In-situ measurements of initial magnetic susceptibility were carried out on sediments of the Pleistocene Sahama Mud Member in order to examine the applicability of susceptibility measurements to correlation of poorly stratified or unstratified sections onshore. The measurements were done in the field at five sites with a handy susceptibility meter (Kappameter KT-9). Our measurements show that there is a linear relationship between values displayed on a KT-9 and volume susceptibilities determined with a Bartington MS2 meter. Despite lithologically homogeneous silty sediments, significant variations in susceptibility were observed at almost all the sites. At one site where four sections 4-5.5 m apart were measured, susceptibility profiles of individual sections were very similar and definitely correlated to each other. Two sites about 150 m apart also showed similar, correlative susceptibility variations. This result suggests that the simple and rapid technique of susceptibility measurements is useful for correlating poorly-stratified or unstratified sedimentary sections on land. To decipher the cause of the observed susceptibility variations, rock magnetic analyses were performed, drawing followings: (1) the section investigated has an admixture of several magnetic constituents, among which the principal contributor to the susceptibility is partly oxidized magnetite or maghemite; (2) the observed variation of susceptibility basically depends on the concentration of such ferrimagnetic minerals.
