REMANENCE CHARACTERISTICS OF DIFFERENT MAGNETIC GRAIN-SIZE CATEGORIESAT XIFENG, CENTRAL CHINESE LOESS PLATEAU

Utilizing the thermal unblocking of low-temperature remanent magnetiza tion in superparamagnetic (SP) ferrimagnets and the low-temperature de magnetization of multidomain (MD) magnetite remanences, the relative p roportions of SP, MD, and single-domain (SD and SD-like) ferrimagnets are estimated in the topmost part of a loess section at Xifeng, China, which covers about the past 130,000 yr. SP ferrimagnets are commonly regarded as pedogenic (authigenic) products while the MD component is believed to have a detrital origin. These measurements, therefore, pro vide new data which improve our understanding of the characteristics a nd distribution of the different magnetic grain-size fractions present in loess and soils. In particular, our measurements indicate a larger MD fraction in soil than in loess, a result which indicates that alth ough enhancement of the SP ferrimagnet fraction dominates the increase d low-field magnetic susceptibility of paleosols, an enhancement of th e MD fraction, probably through leaching, also plays an important role during pedogeneSiS. (C) 1994 University of Washington.