Micromorphology of an Early Holocene Loess-Paleosol Sequence, Central Alaska, U.S.A

Abstract

This paper describes a micromorphological investigation of an early Holocene loess-paleosol sequence at the Chena Hot Springs Road site, a highway road cut exposure near Fairbanks, Alaska, U.S.A. The procedure identified and described soil microstructure, basic mineral components and their related distributions, organic inclusions, and pedogenic features. Micromorphology confirmed the presence of a number of thin, discontinuous, weakly expressed soils that evince disturbance by diagenetic, graviturbative, and cryoturbative processes. Well-preserved organic remains indicate the presence of a boreal forest that would have acted as a highly effective sediment trap. The frequent observation of detrital iron-oxide grains is consistent with other studies of area loess that reveal high concentrations of magnetite and ilmenite, resulting in significant increases in magnetic susceptibility. Increases in wind strength are likely responsible for the increased clay content in the buried paleosols. Loess deposition, which would inhibit pedogenesis, is probably related to greater wind strength, while pedogenesis, indicative of stability and minimal deposition, suggests periods of reduced wind.